Author Topic: Oil change frequency  (Read 962 times)

jpdx

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Oil change frequency
« on: February 02, 2021, 11:45:30 AM »
My vehicle's maintenance schedule says to change the oil (with synthetic) every 7500 miles or 7.5 months. I have been changing every 7500 miles, but with my Mustachian lifestyle it takes me 2-3 years to drive that many miles. Do I really need to change the oil every 7.5 months if I'm driving very little? Does synthetic oil "break down" as quickly as conventional oil?

chemistk

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Re: Oil change frequency
« Reply #1 on: February 02, 2021, 11:55:13 AM »
You definitely should be changing it about annually in your case. Oil breaks down over time, regardless of whether you're driving. Driving just breaks down faster.

This is not to say that your engine is shot if you continue to dive on a few years' old oil, but you're absolutely putting yourself at greater risk for premature engine wear and component failure by keeping the older stuff in. Same thing generally goes with all the fluids.

Given that a DIY oil change should only run you $30 or so (assuming you have the tools to do it), it shouldn't be too much of a pain to just plan on doing it once a year.

Alternatepriorities

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Re: Oil change frequency
« Reply #2 on: February 02, 2021, 12:04:13 PM »
My inner cynic says the manufactures recommendation is designed to optimize their risk of needing to replace the engine before the warranty runs out against the cost of the "free" lifetime oil changes they often wrap into the price of the car... My mobile 1 full synth oil says it will last 15k miles. I use it because it works better at low temps than most oil and don't push it that long.

A DIY oil change is pretty cheap compared to the total cost of driving, so personally I don't go more than a year with the same oil regardless of miles. Our Honda Fit usually gets two per year since we drive it more.

I changed the an old lady's oil once just to be kind... She couldn't remember when it was last changed... A couple of years though. it was pretty gross looking.

YttriumNitrate

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Re: Oil change frequency
« Reply #3 on: February 02, 2021, 12:16:45 PM »
For what it's worth, both my car, and my wife's car use 0w-20 synthetic and the recommended change interval is 1 year or some number of miles that we never reach.

7.5 months seems like an oddly specific interval for oil changes. It kind of seems like the engineers determined 7500 miles was optimal, figured 1,000 miles a month, and called it a day without figuring out how long the oil can actually go when not being used that much.

ChickenStash

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Re: Oil change frequency
« Reply #4 on: February 02, 2021, 12:42:36 PM »
If you are interested in getting some scientific data and a pro opinion, take a sample and send it out for analysis. Blackstone Labs is one place I've used, there are many others out there. They can check for wear metals to give an indication of engine health and also the levels of various additives remaining in the oil and give a recommendation on the change intervals.

RWD

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Re: Oil change frequency
« Reply #5 on: February 02, 2021, 02:15:21 PM »
If you are interested in getting some scientific data and a pro opinion, take a sample and send it out for analysis. Blackstone Labs is one place I've used, there are many others out there. They can check for wear metals to give an indication of engine health and also the levels of various additives remaining in the oil and give a recommendation on the change intervals.
I was going to recommend this as well. You can speculate all you want but the only way to be sure for your exact engine and oil is to send in a sample. I've posted a few of my oil analysis results in my journal (example).

lthenderson

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Re: Oil change frequency
« Reply #6 on: February 02, 2021, 04:37:46 PM »
When I had three vehicles and the third being a spare rarely got more than a thousand miles on it a year, I changed it yearly. I could always see some quite a bit of difference in it over the new oil I put in to replace the old but it wasn't too the point where I thought it was going to do any harm.

SimpleCycle

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Re: Oil change frequency
« Reply #7 on: February 02, 2021, 06:43:29 PM »
We change our oil annually, as we never hit the 5000 mile interval before a year has elapsed.

brooklynmoney

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Re: Oil change frequency
« Reply #8 on: February 02, 2021, 08:35:43 PM »
I bought my first car ever in July. I have driven it 2k miles in the 7 months since. I guess I will change the oil in the spring although by then I estimate I will be at about 3k miles haha.

jpdx

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Re: Oil change frequency
« Reply #9 on: February 03, 2021, 12:05:35 PM »
Thanks everyone. Sounds like the consensus is annual is the way to go. And yes, I take care of oil changes myself so it's no big deal.

HipGnosis

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Re: Oil change frequency
« Reply #10 on: February 03, 2021, 07:10:07 PM »
At 2-3 yrs to get to 7,500 miles and synthetic oil, I would change it annually, and only change the oil filter every other oil change.
I wouldn't worry about the small amount of oil kept in the filter when not changing the filter.
Of course, you have to change your own oil to do it w/o changing the filter.  But this gives you control over which oil and filters you use.   Which also gets them cheaper than the oil shops or mechanics charge.
And, it's the MMM way to do it.

cool7hand

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Re: Oil change frequency
« Reply #11 on: February 04, 2021, 05:52:01 AM »
For those who have a warranty, you'll need records of following the manuf.'s recommended schedule if you ever have a significant claim. Just food for thought.

zolotiyeruki

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Re: Oil change frequency
« Reply #12 on: February 04, 2021, 12:57:00 PM »
For those who have a warranty, you'll need records of following the manuf.'s recommended schedule if you ever have a significant claim. Just food for thought.
C'mon, we're mustachians around here.  None of our cars have fewer than 100,000 miles on them! :P

One more datapoint--my '95 Corolla gets its oil changed twice per year, even though it only gets about 5k miles/year.  I think the recommended interval is 5,000 miles, but I do it that often so that 1) I never exceed the recommended interval, and 2) the oil changes happen when the weather is good.

mntnmn117

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Re: Oil change frequency
« Reply #13 on: February 04, 2021, 04:21:52 PM »
I've read full synthetic breaks down far less and the more miles on the engine you can extend it well past 7,500 mile. Mobil 1 has a version guaranteed for 15k. I've been changing oil on 300k mile Toyota Landcruiser every 10-12k miles or 12-18 months.

v8rx7guy

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Re: Oil change frequency
« Reply #14 on: February 04, 2021, 05:06:55 PM »
Not really the best place to save money, IMO.

jpdx

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Re: Oil change frequency
« Reply #15 on: February 06, 2021, 09:01:56 PM »
OP here. I just changed my oil today, and I'm thinking of installing a Fumoto valve next time. My least favorite step is removing the plug and this should make oil changes easier and cleaner. Just open a valve.

RWD

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Re: Oil change frequency
« Reply #16 on: February 06, 2021, 09:28:37 PM »
OP here. I just changed my oil today, and I'm thinking of installing a Fumoto valve next time. My least favorite step is removing the plug and this should make oil changes easier and cleaner. Just open a valve.
I have had Fumoto valves on three vehicles in the past. They are nice (especially if your vehicle likes to spray oil everywhere when the drain plug is removed like our Legacy did) but there are some downsides to consider as well. Depending on the positioning of your oil pan/drain plug the additional length of the valve could be a risk for catching on something (less ground clearance). This wasn't an issue on our Legacy (behind a plastic skid plate) or BRZ (recessed farther than other parts of the chassis) but I did worry about it sometimes with our Supra. Another thing to consider is that you have to touch the valve directly instead of only touching the wrench for a drain plug. The valve will usually get pretty grimy and the lever itself can sometimes get a stuck and take some effort to switch (it's pretty stubby). Not the end of the world but also not the perfect clean world you might be imagining.

sonofsven

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Re: Oil change frequency
« Reply #17 on: February 07, 2021, 08:22:09 AM »
I used to drive a big diesel van as my work rig, it had an Amsoil two filter set up and drain valve and gallons (I forget how many, it was a lot!) of full synthetic Amsoil oil.
I sent in oil samples every six months to their analytics lab for testing, I changed the oil and filters once a year (about 22k miles/year).
They claimed their oil was good for 100k miles, at least in the big diesels. I sold it at approx 303k miles, still running strong abd testing clean.
With my current Nissan Frontier (177k and counting) I change oil and filter every 5k, with standard dino oil from Costco and Wix filters from my local auto parts house. It's actually less expensive than the Amsoil once a year change, those big rigs (one ton van, so not that big, but 7.3 liter engine!) really cost you.

Syonyk

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Re: Oil change frequency
« Reply #18 on: February 12, 2021, 11:12:41 PM »
A 7.3 Powerstroke is about 3.5 gallons with a filter change.  Make sure the 5 gallon bucket is empty when you start...

In general, "annually" is probably fine for most vehicles driven less frequently, though if you're never getting them hot, you might consider doing it a bit more often.

The major failure modes of oil, as I understand them:
- Just getting dirty.  Oil filters help remove some stuff, but they're normally full flow (all the oil from the oil pump flows through them unless the bypass valve is open with very cold oil), so they can't be tight enough to remove everything and still supply oil to the engine in sufficient quantity.  For a lot of larger engines, you can get "bypass oil filters."  These take a fraction of the flow off the oil pump and run it through a far, far finer filter before returning it to the oil supply, pretty much solving the particulate issue.
- Water in the oil leading to corrosion.  If the vehicle is mostly used for short trips, this is the most common problem - you end up with condensed water from the atmosphere in the oil, and it attacks the engine.  Getting the engine up to full temperature, and holding it there for a while, mostly boils it off (think 45 minutes on the highway).  I think water in the crankcase ends up acidic through a variety of means, which isn't good for the metal.
- The various additive packages wearing out.  There are all sorts of additives in oil to help with various things - buffers to help keep the acidity down, zinc and other metals (not anywhere near enough of it anymore, because it fouls catalytic converters, use diesel oil in old engines) to help protect metal if there's metal contact (it forms a more or less self healing layer), etc.  These just get used up.  If you've got a large engine with good oil monitoring, you can actually get the various packages to add back in as the materials are used up, but this just isn't worth it for most people as opposed to just changing the oil.
- Mechanical shearing of the molecules.  Engine oil (as opposed to transmission oil) is intended mostly for sliding in bearings.  If you run it through gears, it'll actually end up getting cut apart (insert large handwaves here, search for mechanical shear stability if you want the full details) and thinning.  Motorcycles that use engine oil in the transmission tend to be pretty bad about this, and on an old bike, I actually used this as the oil change indicator (the no oil pressure light would start lingering a hair longer on startup and that was my clue to change the oil).  This, unfortunately, you really can't do much about without replacing the oil.  Better quality oil tends to hold up longer, and different engines do this at rather radically different rates.

If you're rolling a ton of miles (especially with an engine that takes a lot of oil), various optimizations make sense.  Bypass filters, oil monitoring, additive packages, etc.

If you're not?  Just change the oil and filter every year if it needs it or not, and see if you can find "oil and filter" combo deals to save a bit on the oil.  For most cases, there's no real reason to run a high end pure synthetic unless required, but I'd avoid the cheapest of the cheap as well.  I tend to run a semi-synthetic diesel blend in most of the motors around here (truck, tractor, motorcycles, property motors - they've got more anti-wear metals in them than automotive oil for gas engines), and run whatever the car wants in it.

I have a lot of overdue oil changes after 2020, though. :/

Morning Glory

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Re: Oil change frequency
« Reply #19 on: February 15, 2021, 05:46:21 AM »
For those who have a warranty, you'll need records of following the manuf.'s recommended schedule if you ever have a significant claim. Just food for thought.
C'mon, we're mustachians around here.  None of our cars have fewer than 100,000 miles on them! :P

One more datapoint--my '95 Corolla gets its oil changed twice per year, even though it only gets about 5k miles/year.  I think the recommended interval is 5,000 miles, but I do it that often so that 1) I never exceed the recommended interval, and 2) the oil changes happen when the weather is good.

I have a 2003 neon with less than 100k miles lol. I live 4 miles from work and bike 6 months of the year. It looks like shit but the heat and AC still work so I'm keeping it. My goal is to retire before that car rusts out, then move someplace warmer so I don't need it.

My husband gets the fancy oil that's good for a year. Sometimes Costco has a sale.

BussoV6

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Re: Oil change frequency
« Reply #20 on: February 23, 2021, 02:41:42 AM »
With regular testing, it is possible for synthetic lubricants to last tens of thousands of miles. Some heavy duty equipment have extremely long change intervals with regular monitoring, filter changes, additive pack maintenance and external filtration.

For private cars/SUVs, I'd always be in the 5000 - 15000 mile range. Shorter intevals if trips are in a dusty environment or mainly short trips. Longer if not. Regular oil changes are cheap maintenance.