Oil changes based on time or mileage?

[bobbyj]

If the manual says 6 months or 10,000 miles, is it ok to wait a lot longer than 6 months if you do not drive that much?

[johnny847]

Following.

Honestly if the manual says do something, you should probably do it. However, the cynic in me says that the car manufacturer benefits from you getting oil changes more frequently (but only if you go to the dealer for servicing).

[Spork]

You're going to get a variance of opinion here...  My opinion is that 6 months means more for conventional oil that breaks down with exposure to oxygen.  I don't really worry about it with synthetic oils.

...but as was said: if you are under warranty, you're better off to follow the manual.  My cars are old enough that warranty isn't a factor.

[bobbyj]

Thanks for the answers.  I found another post on the same subject.  Seems like every 6 months is correct if you are doing short trips, so I guess I'll stick with that.

Thanks

http://forum.mrmoneymustache.com/ask-a-mustachian/oil-change-every-6-months/

[Syonyk]

It depends heavily on the driving, type of driving, and somewhat on the type of oil.

If you have a lot of oil to change, it's often worth the oil analysis ($25 or so) to find out when you actually need to change it, but for most people this isn't worth the savings (unless you seriously geek out over engine oil).

There are several things to consider with oil degradation.

- Water.  When the engine runs, it cycles air into the crankcase, and temperature cycles (day/night swings) will bring air into the crankcase as well.  The water, if not boiled out, will eventually need to be removed.  If you do a lot of long highway driving, the oil gets hot enough to get the water out, and this is less of a factor.  For short city driving, or cold weather driving, the water builds up.
- Combustion blowby.  This is dependent on your engine, but a loose engine with a lot of blowby will crud up and acid up oil a whole lot faster than a tight engine.
- Sheer.  This isn't normally an issue with cars, but for motorcycles that share engine oil with the transmission, the transmission gears rip up the oil and it will sheer down to a much thinner oil by the time it's due for replacement.

I'd suggest an "or" approach to oil changes - either the specified number of miles for severe duty service (everything you do is severe driving... nobody, ever, meets the "normal service" requirements), or a given number of months.  At least every year, but it could be more frequent depending on the engine.

Look into how picky your car is.  Certain turbocharged engines are very, very picky, and need aggressive oil change schedules to avoid coking and damage.  Others are a lot less picky.

[Cole]

I have never based my oil change intervals on time. I base mine solely on mileage (I drive about 20k miles a year UGH). Synthetic oil basically never degrades. It loses its additives and the filter can get clogged but the oil is effectively the same. In the spirit of full disclosure I change my oil every 7-10k miles on a car that recommends an oil change every 3k (Its 18 years old). I also went to diesel technical school though and heard a lot of advice from old timers.

[tj]

I change mine when the maintenance minder says so.

[a1smith]

I change mine when the maintenance minder says so.

So do I.  They are more mileage based (along with engine hours, rpm, temp, load, etc) than time based (since ECM doesn't know how long car is parked between times of operation).

[Spork]

I change mine when the maintenance minder says so.

So do I.  They are more mileage based (along with engine hours, rpm, temp, load, etc) than time based (since ECM doesn't know how long car is parked between times of operation).

I don't know about yours, but mine are exactly mileage based, ignoring all else.

[a1smith]

I change mine when the maintenance minder says so.

So do I.  They are more mileage based (along with engine hours, rpm, temp, load, etc) than time based (since ECM doesn't know how long car is parked between times of operation).

I don't know about yours, but mine are exactly mileage based, ignoring all else.

Mine is a Chevy.  GM vehicles use an algorithm that looks at more than just mileage.  So, each oil change interval is a little different depending on how the vehicle was driven.

[tj]

I change mine when the maintenance minder says so.

So do I.  They are more mileage based (along with engine hours, rpm, temp, load, etc) than time based (since ECM doesn't know how long car is parked between times of operation).

I don't know about yours, but mine are exactly mileage based, ignoring all else.

My Honda Civic isn't mileage based. it's been various. Also, I've had the oil pop up as low on its own without a maintenance minder alert.

[patrickza]

I've always thought a good measure would be to base it on amount of fuel used. That way if you're a hard driver it would be more often, if you do mostly freeway driving, less often.

My car recommends 15000km/every year. Personally though I service every 15000km, which for me is about every 18 months. The stealership has never asked why I didn't come in at 12 months, and the car is still in great shape.

[a1smith]

Here is an article about GM's oil life calculation.  They reference an SAE paper at the end which goes into more specifics.

GM's Oil-Life System Improves Timing of Oil Change

[FIRE me]

I get Mobil One synthetic cheap by way of rebate, and I change the oil and filter once a year. I drive 5,500 miles per year.

[sequoia]

I get Mobil One synthetic cheap by way of rebate, and I change the oil and filter once a year. I drive 5,500 miles per year.

Mobil One synthetic for both vehicle. Vehicle 1 only driven around 5K/yr, so it gets oil change once a year. Vehicle 2 is driven around 5-6K/6months with lots of short trips, stop and go. It gets oil change every 6 months. I do oil change and other maintenance in Spring and Fall, when the weather is nice out, so the number of miles for each oil change is not exact.

[Joggernot]

Changed oil early this month.  Toyota Tacoma got Mobil 1 and filter after 3500 miles and one year.  Honda Accord got Mobil 1 and filter after 5500 miles and one year.  I change oil once a year as a minimum, based on the owner's manual.  The Tacoma gets a lot of short miles around town hauling gardening supplies, etc. so the one year is probably appropriate.  The Accord gets the longer trips.

If the Tacoma drops below 3000 miles in one year, I will let it go until I at least get the 3000 miles out of the oil.  Or I'll move to dino oil to save money.

[TrMama]

My car recommended every 6mo or 8,000km. When I started driving fewer than 8,000km/6 months I switched it over to synthetic. Synthetic doesn't break down over time the way conventional oil does so now I ignore the date and just change it when I hit the mileage requirement (every 18mo).

[zolotiyeruki]

I use plain ol' dino oil, and change it every 6 months (spring/fall, like sequoia), whether it needs it or not.  One car gets about 10k/year, the other gets *maybe* 2500, but I use the same schedule for both.

[paddedhat]

Here is an article about GM's oil life calculation.  They reference an SAE paper at the end which goes into more specifics.

GM's Oil-Life System Improves Timing of Oil Change

If this article was any older it would be written on Parchment, with a quill pen. In the last several decades, many have discovered that "maintenance minders" fail in one critical area. They have no idea how much dirty air your engine is sucking in. Continually operate your vehicle in a dirty environment, with poor filter maintenance, and a few of those recommended 11K change intervals, and you might find yourself buying a new engine pretty quickly. GM and others have also issued TSBs, or dealer only notices, to greatly shorten change intervals in some cases, as their minder systems and extended changes were resulting in serious issues with warranty costs, and lawsuits. I do all my vehicles with Mobil One, and a quality Purolator filter, at 5K intervals. I have little interest in proving that 8-12K intervals are just fine, especially give the very steep cost of being wrong on this issue. Several vehicles I have owned are now in the hands of friends and business associates who are still operating them in the 300-400K range on the ODO. It may of cost a few hundred more in maintenance cost to get them to last this long, but it's hard to argue with the results. If you are driving very few miles and not changing your oil at least every year, or listening to a maintenance minder and changing oil in the 8K+ range, good luck with that.

[flyingaway]

Whatever the manual says, I double it.

[a1smith]

Here is an article about GM's oil life calculation.  They reference an SAE paper at the end which goes into more specifics.

GM's Oil-Life System Improves Timing of Oil Change

If this article was any older it would be written on Parchment, with a quill pen. In the last several decades, many have discovered that "maintenance minders" fail in one critical area. They have no idea how much dirty air your engine is sucking in. Continually operate your vehicle in a dirty environment, with poor filter maintenance, and a few of those recommended 11K change intervals, and you might find yourself buying a new engine pretty quickly. GM and others have also issued TSBs, or dealer only notices, to greatly shorten change intervals in some cases, as their minder systems and extended changes were resulting in serious issues with warranty costs, and lawsuits. I do all my vehicles with Mobil One, and a quality Purolator filter, at 5K intervals. I have little interest in proving that 8-12K intervals are just fine, especially give the very steep cost of being wrong on this issue. Several vehicles I have owned are now in the hands of friends and business associates who are still operating them in the 300-400K range on the ODO. It may of cost a few hundred more in maintenance cost to get them to last this long, but it's hard to argue with the results. If you are driving very few miles and not changing your oil at least every year, or listening to a maintenance minder and changing oil in the 8K+ range, good luck with that.

I just found the first article I could that described Shirley Shwartz's work on the oil life system; I didn't exhaustively search for the latest and greatest update on the algorithm.  SAE can't afford to print their conference papers on parchment, they just use regular paper and laser printers, even back in 1987!  ;-)

I use the engine oil life system in my Chevy Sonic and it has never given us an oil change interval longer than about 7.5k miles.  The owner's manual also states not to go over one year between oil changes. See page 11-2 in the 2014 Chevy Sonic owner's manual.

Engine Oil Change
When a : % CHANGE message displays in the DIC, have the engine oil and filter changed within the next 1,000 km/600 mi. If driven under the best conditions, the engine oil life system might not indicate the need for vehicle service for more than a year. The engine oil and filter must be changed at least once a year and the oil life system must be reset. Your trained dealer technician can perform this work. If the engine oil life system is reset accidentally, service the vehicle within 5 000 km/3,000 mi since the last service. Reset the oil life system when the oil is changed. See Engine Oil Life
System on page 10-12.

dexos1 qualified oils, which is what is recommended by the owner's manual, are semi-synthetic oils.  dexos1 oil also has an additive package designed for the stated oil change intervals in the owner's manual.

Even though the ECM doesn't know how dirty the air is the driver does.  And changing air filters at the proper intervals is just as important as changing the engine oil.

Additionally, Ford increased their oil change interval from 5,000 miles to 7,500 miles in 2007.  So, it is not just GM.

Speaking of lawsuits, Jiffy Lube International has a class action lawsuit in California over 3,000 mile recommended oil change interval - Will the 3,000-mile oil change open you up to a lawsuit?

Can you list one of the GM Technical Service Bulletins (TSB) that you are referring to?

[Joggernot]

No one has mentioned the site, "Bob is the oil guy".  He has some good information based on research/work he has personally done.

http://www.bobistheoilguy.com/motor-oil-101/

[paddedhat]

I just found the first article I could that described Shirley Shwartz's work on the oil life system; I didn't exhaustively search for the latest and greatest update on the algorithm.  SAE can't afford to print their conference papers on parchment, they just use regular paper and laser printers, even back in 1987!  ;-)

Sorry, but anything on a topic like this, dating back decades, deserves a poke. As for the blather from the SAE, I'll stick with what I read and hear from techs. in the field. If they are fixing major engine damage after the car owner religiously followed the oil change minder, and did a series of 10-15K interval changes, yet grenaded at 125K miles, I tend to give that more weight.

I use the engine oil life system in my Chevy Sonic and it has never given us an oil change interval longer than about 7.5k miles.  The owner's manual also states not to go over one year between oil changes.

7.5K is a bit closer to reality, IMHO. I had several older, 2003-2007 GM products that would easily go 8K on the OCM while they were being used for extremely severe towing duty, or 11-12K when doing lighter work. Naturally, this information was used as entertainment, not as a maintenance schedule.


dexos1 qualified oils, which is what is recommended by the owner's manual, are semi-synthetic oils.  dexos1 oil also has an additive package designed for the stated oil change intervals in the owner's manual.

GM has a pretty flaky history of playing chemical engineer. There Dexcool was such a disaster I find it to be a bit ballsy to be still using the name on other products that they would want the public to believe in. As for longevity additives, all top brands have them., per various SAE standards.

Even though the ECM doesn't know how dirty the air is the driver does.  And changing air filters at the proper intervals is just as important as changing the engine oil.

Correct, and one of the most ignored tasks. This being is one of many reasons why the whole "let the computer algorithm maintain my car" concept can really end up hurting those of us that do not dispose of cars as frequently as the manufacturer would like. 

Additionally, Ford increased their oil change interval from 5,000 miles to 7,500 miles in 2007.  So, it is not just GM.

Extending, or eliminating maintenance, is a key technique in creating the delusion that cars are essentially maintenance free. Sealed transmissions that allegedly do not need to be serviced or checked for fluid levels, ever, extended oil changes and other selling points do little for the crowd that wants to keep a vehicle for 200-300K miles.

Speaking of lawsuits, Jiffy Lube International has a class action lawsuit in California over 3,000 mile recommended oil change interval -

Deceptive business practices are hardly a story. Taking your car to Jiffy Lube and getting screwed is something that most of the intelligent folks on this forum know to avoid. I can take my Honda to a dealer, a month after I install new cabin and engine and filters. The very first thing they do is to send the service writer to the waiting room to tell me that they checked them, and recommended that they be replaced. This is not class action lawsuit material, it's the way they all do business. It's my job to say, "the car is here for a warranty repair, NOT for you to dig through it looking for high profit items to replace"


Can you list one of the GM Technical Service Bulletins (TSB) that you are referring to?

Very first Google hit on   "TSB to modify GM oil change frequency" was about reflashing to lower intervals on 2010 Acadia due to excess timing chain wear. Doesn't matter if it's GM, VW. BMW etc. they all have TSBs out there, silent recalls, and quietly address the fraud that is the oil change minder system.  When you have a system that tells you that everything is ducky when you go 10-15K between changes, You lose.

[a1smith]

Google modifies search results based on search history, etc. so your 1st hit is not my 1st hit.

Here is my first hit.

http://www.aftermarketsuppliers.org/Councils/Filter-Manufacturers-Council/TSBs-2/English/94-1R1.pdf

It is a TSB but not a GM one and they don't reference what you mention.  Can you post the link on your 1st hit so I can read it?  Thanks!

[paddedhat]

Various GM products

www.enclaveforum.net/index.php?topic=7827.20;wap2

http://community.cartalk.com/discussion/2246797/gm-customer-satisfaction-program-recall-of-3-6l-v6-engine

http://wot.motortrend.com/gm-shortens-oil-change-interval-warnings-for-779000-vehicles-352839.html

BMW's decision to go from 15K to 10K intervals, and/or two years to one between changes, on all new cars in 2014

http://f10.5post.com/forums/showthread.php?t=868294

If you dig deeper you will find additional evidence on enthusiasts websites. There is some particularly interesting stuff done by the VW crowd, using oil analysis that proves that the factory recommended 10K intervals in many specific VW engines, particularly turbo equipped ones, is not producing acceptable results, and resulting in wear and sludging issues. 

I've said it many times before. You can trust the algorithm to determine the fate of your $5,000 plus engine, and hope it dealt with all the intangibles like particulate pollution, acid and water build accumulation, degradation of the additive package, etc.... or you can use a quality synthetic and filter, and do the work yourself, every 5K. The difference in cost? About a third of a cent per mile.  The difference in longevity? I have seen it make the difference between an engine that was a sludged up boat anchor at 125K miles on it, and a duplicate, but properly maintained one,  that looked new when the heads were pulled. Your money, spend it however you want.

By my thinking, at 0.003 per mile in additional operating costs, it becomes a conversation that's not even worth having.

[Papa Mustache]

I change my oil normally at 5K miles with Mobile 1 and a Wix/NAPA Gold filter.

An old timer told me to change it my oil when the oil gets dirty enough that I can't read the markings on the dipstick.

You know what? Around here that is about 5K miles unless I'm working my car hard (short trips, really extreme weather, etc).

We also have a number of collector cars in the family. We've been changing those cars about once per year with nary a problem for 30 years. These cars hardly run 3k-4K a year which might resemble the habits of frequently bicycling MMM readers.

So far my Hondas have lasted north of 300K miles. For many of you in different parts of the country - the salt will get your car before the engine wears out. Don't worry about the oil changes. Just pick an interval and get it done. My interval works out to once in the spring and again in the fall before it gets too cool. We carpool alot.

[libertarian4321]

Manufacturers will recommend that you do "maintenance" with ridiculous regularity (let me guess, they recommend that you do the maintenance at THEIR facility?).

Why?  BECAUSE THEY MAKE MONEY FROM IT!

And even if you get your oil change done somewhere else, e.g. a quick lube place, they'll recommend you come back every 3K miles.

Because your car needs it?  Hell no.

Because they make $35 every time you show up.  And if you show up every 3k miles, instead of 5k or 7k miles, they make more money.

I do my oil about every 5k, regardless of the time (what, that oil that was made 6,000,000 years ago is going to "go bad" sitting in your engine if you wait more than a year?).  I could probably safely do it even less often.

My 14 year old Truck is running just fine...

[BlueMR2]

Both of my cars say to do 3000 miles or 3 months, whichever comes first.  The oil I use says 15000 miles or 1 year whichever comes first.  What I'm actually doing is every 3000 miles.  Sometimes it's less than a year, sometimes more (I drive around 7,000 miles a year total, but it's spread across 2 cars and a motorcycle)...  :-)

The motorcycle is listed at 3500 miles or 1 year, with 15000 mile or 1 year oil.  I just do it yearly as it only gets hundreds of miles.  If I waited for mileage it could be a decade, which is probably a bit much...

A few of the racers I know that only do a few hundred miles a year just change the oil every 5 years.  Doesn't seem to be causing them any harm, but would make me nervous.

[patrat]

Two options:

Follow the manual schedule, time or mileage whichever comes first. Use cheap oil that meets specs, I usually found the cheapest oil was a house brand at walmart (outside of good sales... subscribe to an alert for "motor oil" at slickdeals). I aim for just a hair over $2/ a quart, although it fluctuates. The "cheap" purolator filters are pretty good.

OR

Use a premium synthetic with a matching filter, which as a pair is warranted by the oil manufacturer for an extended change interval. I just switched to this, when Mobil was running a sale on their extended change oil and filter (thanks slickdeals). The cost per year came out to be a little less this way, and 1/2 to 1/3 as much work, not counting time researching and sending rebates.

My scenario was a Toyota that uses ~5 qt of 5w30 or 5w20, on a 6 month/5000 factory interval. With the extended oil, Mobil guarantees 1 year/15000 mile intervals. There was a $30 rebate at the time on 10 quarts with 2 Mobil filters, and I found where the oil and filters were at their best price. Previously I had stocked up on a 2 year supply of oil for free, when valvoline introduced their "green" recycled nexgen oil with crazy good rebates (thanks slickdeals).

You can do the used oil analysis, but I think it really only helps if you are geeking out with high dollar engine oil, or running a fleet of vehicles and taking an example from the fleet to establish your own intervals for the fleet. Neither really fits the role for a frugal DIY person.

Arguments for high dollar oil are hard to make when the cheaper oil has the car still running well, without oil related engine failure, at high mileage / when you resell it. Although sludging anecdotes exist for certain oils, looking at the oil bottle will tell you what ILSAC/API standards it meets. The standards are pretty good. I haven't personally seen a failure that could be attributed to a particular oil brand. The oil geeks over at Bob is the Oil Guy also seemed to conclude that store brand oils were relabeled middle of the line oils, with good performance.

[BlueMR2]

Although sludging anecdotes exist for certain oils, looking at the oil bottle will tell you what ILSAC/API standards it meets. The standards are pretty good. I haven't personally seen a failure that could be attributed to a particular oil brand. The oil geeks over at Bob is the Oil Guy also seemed to conclude that store brand oils were relabeled middle of the line oils, with good performance.

From what I recall, it's certain engines combined with "regular" oil (of any manufacturer) that are the sludging issues.  There was a whole big mess with I believe it was late '90's/early 2000 ish Toyotas.  IIRC as part of meeting the latest emissions specs they narrowed some oil passages to keep temperatures higher, which resulted in sludge related failures a few years later when paired with the (recommended) dinosaur oil.  People running synthetic didn't have the issue.

I lost an early '90's Toyota engine to sludge.  It killed the oil pump gradually over time, so I was getting just under 10 psi out of it by the time I started hearing rod knock.  Normal pressure at cruise is 60 psi.  The warning light comes on between 5-7psi...  Cylinder bores were torn up.  It was obviously wearing for a long time like that.    We were able to salvage the crank and the block.  Block had to get overbored and everything else ended up getting replaced.  $4500.  I run synthetic in the rebuilt.  :-)

[Spork]

This may border on an "old wives tale".  But I'll leave this here anyway.

I will add to this... I've always heard to pick an oil and stick with it.   Changing brands/formulations will end up leaving different additives, detergents, etc behind that were never intended to mix.  These are what will end up causing sludge or even removing sludge build up that wasn't bothering anything.

I'll add my doesn't-mean-a-thing anecdote.  Some 30+ years ago, when I was in college, my roommate bought an old Nova.  It was ugly but ran fine and didn't leak or burn oil at all.  At the first oil change, instead of going with what the previous owner had used, he bought whatever was on sale.  The detergents in that oil seemed to "clean out" all the build up over the years ... and that damn thing leaked like a sieve from the front main seal from that day forward.  It was 3 hours from college to home.  He stopped once an hour to add another quart of oil.

[KarefulKactus15]

Il chime in. I go by whichever comes first.   10k Miles or once a year on synthetic.   Although these oil threads crack me up.   Other then extreme cases where oil was never changed, I've never seen a high mileage car fail from "lack of oil changes early in life".   Its always the transmission in my experience that finally bites the dust, probably due to lack of fluid change lol

[Spork]

Il chime in. I go by whichever comes first.   10k Miles or once a year on synthetic.   Although these oil threads crack me up.   Other then extreme cases where oil was never changed, I've never seen a high mileage car fail from "lack of oil changes early in life".   Its always the transmission in my experience that finally bites the dust, probably due to lack of fluid change lol

...And yet, newer cars (Toyota is one I've personally noticed) are starting to specify never-change transmission fluid.

[AlexK]

In 2006 my friend and I both bought new Toyota Yarises (Yarii?). Last month that friend had a shoulder injury and his car was overdue so I changed the oil in it for him. The oil fill hole area in his car was cruddy with caked on gunk. Mine is spotless and still looks new. We both use Mobil 1 with the difference being I was changing oil at 5k intervals and he was doing 10k. My car has 100k and his 140k so that could be part of it but his looked 1000 times worse not 40% worse.

On a side note the Yaris is an excellent car. Neither has ever had a single issue.

[HipGnosis]

  Its always the transmission in my experience that finally bites the dust, probably due to lack of fluid change lol

...And yet, newer cars (Toyota is one I've personally noticed) are starting to specify never-change transmission fluid.

Not "yet"...  It is BECAUSE owners never changed fluid that the MFG's are now making transmissions that don't need it.   Transmissions that needed fluid changes were the 'weak link' of the cars. 

[Syonyk]

And that sealed transmission fluid will absolutely last the life of the warranty!  Beyond that?  Good luck.  If you're gentle, it'll be fine for a while longer.  If not, it won't.  Once the fluid wears out, the transmission will follow.

Heat is the enemy of transmission fluid for automatic transmissions.  Keep the transmission fluid cool, the transmission will last a long time.  Get it hot, your transmission life will drop dramatically.  Get it too hot, your transmission life is measured in tens of miles to failure.

This is why pretty much all serious towing trucks have transmission temperature gauges and extra transmission coolers - a well built automatic will tow a house, as long as you keep it cool.  If your transmission temps in the pan are above about 160-180F, the fluid is going to be too hot in the working parts, and it's life will be shortened.  It's about 20F per "half life drop" of the transmission fluid - so only 40F too hot, and your fluid life is cut in four.

Manual transmissions are easier.  Do they have fluid in them?  Has it been changed in the last, oh, 150k miles?  Then it's fine.  And they let you know very clearly when they're getting unhappy with their fluid, but they don't overheat it like an automatic under load will.

[Spork]

  Its always the transmission in my experience that finally bites the dust, probably due to lack of fluid change lol

...And yet, newer cars (Toyota is one I've personally noticed) are starting to specify never-change transmission fluid.

Not "yet"...  It is BECAUSE owners never changed fluid that the MFG's are now making transmissions that don't need it.   Transmissions that needed fluid changes were the 'weak link' of the cars.

I would suspect the main reason owners never changed the fluid was because it was a pain in the ass.  If they'd put a damn drain plug on there, you could do multiple partial changes really easily.  Oddly, the "no change needed" transmissions now DO have a drain plug.

I'm still on the fence on the no-change transmission.  I see lots of arguments back and forth on whether to do it or not.  So far ... I haven't caved in and changed it.

[Syonyk]

You'll never hurt a car by changing fluids too often.

[music lover]

I change it once a year...but I only drive 10k kilometers (6200 miles) a year. I always use synthetic oil.

[TechMike]

You'll never hurt a car by changing fluids too often.

But it will hurt your wallet.

My cars (I still need to convince myself to sell one) get driven so little that I never change for mileage. I always change the oil every six months, regardless. At $15 to do it myself each oil change, that's only about $60 a year on oil changes. $30 if I can convince myself to sell the rarely driven SUV.

[Syonyk]

You'll never hurt a car by changing fluids too often.

But it will hurt your wallet.

Sure.  But a fluid change every so often to avoid a transmission rebuild seems worth it, even if the transmission is "sealed for life."  All that phrase actually means is, "We're pretty confident it will make it out of the warranty period with no fluid changes."

Some older engines were well known to sludge up without frequent oil changes, and at least some turbocharged engines are *very* picky about it and will proceed to coke up the oil and fry turbo bearings if you're not religious about oil changes.

[BlueMR2]

///some turbocharged engines are *very* picky about it and will proceed to coke up the oil and fry turbo bearings if you're not religious about oil changes.

Well, usually the root cause is people that don't read the owner's manual...  Turbo cars normally have an idle down time period which you must observe to avoid oil coking in the turbo.  Car people know this.  Average Joe consumer does not (and doesn't read the manual to learn it either).  Luckily it's less of a thing nowadays with water cooled turbos (but even my oiled AND water cooled turbo car has idle down times in the manual!)...