Author Topic: Hypermiling tips?  (Read 3849 times)

Riptoast

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Hypermiling tips?
« on: July 06, 2016, 09:59:41 PM »
I've just recently started getting interested in hypermiling, and have been testing out some of the basic driving techniques for increasing my fuel economy. Things like accelerating slowly, cruising in a higher gear, shifting to neutral when on long descents or rolling up to far off red lights, and minimizing braking and stops seem like common sense. Does anyone have experience with the more involved tricks like turning your engine off while coasting down the road, then dropping the clutch in to restart when needed? What gear would you do that in? And what is the most efficient way to descend a long, steep, mountain road--should I engine brake to save my brake pads or try to coast some to save on gas? I'm all about getting better mileage, but I'm hesitant to try anything that might be remotely dangerous, it just doesn't seem worth it.

Tester

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Re: Hypermiling tips?
« Reply #1 on: July 06, 2016, 10:06:37 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.
More, if you don 't use the engine brake you even risk overheating your brake fluid which believe me is not fun at all when you are going downhill.

Choices

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Re: Hypermiling tips?
« Reply #2 on: July 06, 2016, 10:08:19 PM »
Please keep in mind that 'dangerous' can mean different things in different places. It's one thing to try new techniques while driving a secluded road in the mountains, and another to try techniques that are not typical in big cities.

Other drivers might be annoyed and tailgate or develop road rage, or they might just be distracted, on their phones, or drunk/high. I'm not saying that either of these possibilities is all your fault or in any way acceptable, just that if your goal is to avoid accidents and promote safety in addition to getting excellent mileage, it might be worth your while to drive as others expect you to when others are around.

I can tell you many horrifying traffic tales from the emergency department.

WerKater

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Re: Hypermiling tips?
« Reply #3 on: July 06, 2016, 11:21:06 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.
More, if you don 't use the engine brake you even risk overheating your brake fluid which believe me is not fun at all when you are going downhill.
Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.
- On a significant slope (which sounds what was described here) where you would have to break if coasting, it indeed makes no sense. You will be burning the gas for no good reason and also using your brakes more than necessary.

Accelerating slowly is often not fuel efficient. The most efficient way of accelerating is with almost 100% throttle, shifting up as early as possible.
Cruising in high hear is good. Always be in the highest gear possible (i.e., where your engine makes no funny noises).

Coasting with engine off is practically never worth it. The savings are minuscule (my car for example uses only 0.7L gas per hour of idling). And many of your drive assistance stuff will not really be working. Most importantly the brake booster will not be recharged, after you have used it up.

On a side not concerning this: If you have access to somewhere away from traffic (and other obstacles; like a big empty parking lot), you should try to brake without the booster to see how it feels: Accelerate to a fairly high speed (maybe 80km/h), shift to neutral, shut down the engine, then brake abit, release the brake, repeat. In the beginning it will work like always (booster still working). But as soon as it has used up its vacuum, you will feel as if the brake is not doing anything anymore. But it's not quite true. If you hit the brake with all the force you have, you will be able to stop the car, but it will take a bit. It's an interesting experience and knowing how it feels might save your butt one day, if your brake booster ever fails for any reason.
 

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Tester

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Re: Hypermiling tips?
« Reply #5 on: July 07, 2016, 08:36:29 AM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.
More, if you don 't use the engine brake you even risk overheating your brake fluid which believe me is not fun at all when you are going downhill.
Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.
- On a significant slope (which sounds what was described here) where you would have to break if coasting, it indeed makes no sense. You will be burning the gas for no good reason and also using your brakes more than necessary.

Accelerating slowly is often not fuel efficient. The most efficient way of accelerating is with almost 100% throttle, shifting up as early as possible.
Cruising in high hear is good. Always be in the highest gear possible (i.e., where your engine makes no funny noises).

Coasting with engine off is practically never worth it. The savings are minuscule (my car for example uses only 0.7L gas per hour of idling). And many of your drive assistance stuff will not really be working. Most importantly the brake booster will not be recharged, after you have used it up.

On a side not concerning this: If you have access to somewhere away from traffic (and other obstacles; like a big empty parking lot), you should try to brake without the booster to see how it feels: Accelerate to a fairly high speed (maybe 80km/h), shift to neutral, shut down the engine, then brake abit, release the brake, repeat. In the beginning it will work like always (booster still working). But as soon as it has used up its vacuum, you will feel as if the brake is not doing anything anymore. But it's not quite true. If you hit the brake with all the force you have, you will be able to stop the car, but it will take a bit. It's an interesting experience and knowing how it feels might save your butt one day, if your brake booster ever fails for any reason.

I would say that losing the steering "booster" is also a concern when coasting with the engine shut off.

SoccerLounge

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Re: Hypermiling tips?
« Reply #6 on: July 07, 2016, 08:07:49 PM »
Accelerating slowly is often not fuel efficient. The most efficient way of accelerating is with almost 100% throttle, shifting up as early as possible.

THIS! There are two reasons this is true: a partially-open throttle body being less efficient, and faster acceleration enabling you to sooner shift into higher gears which provide less engine braking / drag to oppose the engine. On my car, a manual-transmission early-2000s hybrid, my shifting pattern is usually 1-2-5 (with 5th gear being the top). I only use 3 and 4 sparingly, if absolutely necessary, on hills.

Also, use as little gas / throttle as possible to maintain the speed you want to. This sounds like a no-brainer, but often when cruising at low rpm in a high gear, mashing the throttle will cause no perceptible speed increase but just waste a bunch of fuel. If you really have to speed up quickly, downshift. Otherwise, take your time, stay feather-light on that gas, and let the high gear slowly speed you up at its own pace. Unless that's going to seriously cause other drivers a problem; I try not to be 'that guy' who goes 25mph below the limit rather than 5mph below it, etc.

APowers

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Re: Hypermiling tips?
« Reply #7 on: July 09, 2016, 10:52:53 AM »
Ecomodder is a great resource.

In general, shift up early, keep your rpms low, keep the air conditioning off, and minimize drag (keep your tire pressures up, roof racks off, etc). I was surprised at the fact that I could be in 5th gear as low as 20-25 mph. Changing my tire pressure from ~35psi to ~45-50psi made a noticeable difference in coasting performance.

Brake as little as possible, accelerate as little as possible. The whole struggle of transportation is against friction and inertia; you fight friction by reducing drag, you fight inertia by reducing the need for changes in velocity-- the less you need to brake or accelerate, the less work is needed, and the less fuel consumed.

Gimesalot

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Re: Hypermiling tips?
« Reply #8 on: July 11, 2016, 08:28:07 AM »
I know that this isn't a true hypermiling tip but it is the one that I find the most useful:

Get to know the timing of the lights on the streets you normally drive.

For example, if I go the speed limit on my way to work, I will get stopped by most lights.  If instead, I go 5 miles over the speed limit, there are no lights to worry about.  It seems stupid that they time it like that, but it is what it is.

ketchup

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Re: Hypermiling tips?
« Reply #9 on: July 11, 2016, 09:15:40 AM »
Before you start worrying about wacky things like engine-off-coasting, cover the basics:

Keep all your maintenance up to date.  Fix problems when they show up.
Don't go any faster than you have to, especially in stop-and-go situations.
Related: Drive so that you have to brake as little as possible.  That's energy wasted and brake pads worn down.
Turn off extra energy sucking stuff in your car (air conditioning mostly).
Make sure your tires are at the proper pressure and you're not carrying more weight around than you need (leave your bowling ball collection at home).

If you drive a manual:
Follow what others have said about accelerating with high load and low RPMs.

If you drive a hybrid:
Brake as gently as possible to let the regen brakes do their thing and so you don't burn out your real brakes as quickly.

I recently switched from a manual-transmission old car to a newer CVT hybrid and driving for efficiency is quite a different beast with the hybrid (city driving being more efficient than highway driving makes my brain hurt).

MoneyCat

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Re: Hypermiling tips?
« Reply #10 on: July 11, 2016, 09:43:36 AM »
The best hypermiling comes from driving a used hybrid (which are pretty cheap these days because hybrids have been around for fifteen years now). Then you gently brake when necessary to recapture as much kinetic energy as possible, then cruise around town using the electric motor. On some trips I've taken in my Ford Fusion Hybrid, I have rolled down hills on local roads at the speed limit and then completed my trip on electric power. Best MPG so far for a shopping trip was 70.7 MPG.

Riptoast

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Re: Hypermiling tips?
« Reply #11 on: July 11, 2016, 05:00:17 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.

I admit I don't know much about engine efficiency, but do you mean that engine braking uses no more gas than idling would, and that coasting in neutral with the engine on actually uses more than just idling? If someone could explain that a bit it would be much appreciated.

Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.

Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

Tester

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Re: Hypermiling tips?
« Reply #12 on: July 11, 2016, 05:30:13 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.

I admit I don't know much about engine efficiency, but do you mean that engine braking uses no more gas than idling would, and that coasting in neutral with the engine on actually uses more than just idling? If someone could explain that a bit it would be much appreciated.

Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.

Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

For modern cars engine brake means zero fuel is used.
The computer detects what is happening and cuts of the fuel.

So, if you use engine brake, zero fuel used.
If you use neutral, idling fuel is used.

Now, there are other things which get more wear from engine braking - instead of using the brake pads you use the transmission...
But after I experienced brake fading because of a long descent with high speeds and long braking before corners I really prefer engine braking and lower speeds - if someone is pushing me over the reasonable speed they can go jump from a cliff if they want.

I was lucky that I knew fading can happen in that kind of traffic so when it started I was still able to safely get off the road and stop the car - the brake did not fade completely.

Spork

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Re: Hypermiling tips?
« Reply #13 on: July 11, 2016, 05:36:06 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.

I admit I don't know much about engine efficiency, but do you mean that engine braking uses no more gas than idling would, and that coasting in neutral with the engine on actually uses more than just idling? If someone could explain that a bit it would be much appreciated.

Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.

Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

For modern cars engine brake means zero fuel is used.
The computer detects what is happening and cuts of the fuel.

So, if you use engine brake, zero fuel used.
If you use neutral, idling fuel is used.

Now, there are other things which get more wear from engine braking - instead of using the brake pads you use the transmission...
But after I experienced brake fading because of a long descent with high speeds and long braking before corners I really prefer engine braking and lower speeds - if someone is pushing me over the reasonable speed they can go jump from a cliff if they want.

I was lucky that I knew fading can happen in that kind of traffic so when it started I was still able to safely get off the road and stop the car - the brake did not fade completely.

I believe the confusion (and I was confused, too) is in the terminology.

"Engine braking" generally refers to using the engine to slow the car down.  I.e., downshifting.  It DOES use more fuel.  It usually (but not always) refers to manual transmissions.  I can assure you:  if you do that with a modern manual transmission, the engine will rev and you will use more gas.  I suspect it is also true of a modern automatic transmission.  If you shift from "overdrive" into L2 or L1... you'll burn more fuel.

I think the Tester is referring to a modern day automatic transmission car where the transmission is left absolutely alone in the "overdrive" selection.  Personally, I would not call this engine braking.  There is no engine braking going on.

SoccerLounge

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Re: Hypermiling tips?
« Reply #14 on: July 11, 2016, 05:42:46 PM »
[Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

It's not black and white, and has to do with when various models of cars turn off the fuel injectors. But it also depends on things like how much drag the highest gear puts on the engine vs. the (tiny) amount of extra fuel used when coasting in neutral (assuming you're driving a car that injects a small amount of fuel in neutral vs. none when in gear with zero throttle because in the latter case the transmission helps turn the engine over but in the former case there has to be enough fuel to overcome engine inertia)... etc!

I'd give more tips, but the Insight is an odd beast; there is no electric-only power at all - it's electric-assists-gas vs. gas-assists-electric - and so driving it is an odd, well, hybrid of the driving styles of something like an Echo and something like a Prius. Both of which I think are fun to drive, btw. I think there are some of us that get our kicks from well-designed efficient cars and high mpg, instead of from going 50mph over the speed limit and blasting away from the stop sign :)
« Last Edit: July 11, 2016, 05:44:38 PM by SoccerLounge »

Tester

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Re: Hypermiling tips?
« Reply #15 on: July 11, 2016, 06:00:42 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.

I admit I don't know much about engine efficiency, but do you mean that engine braking uses no more gas than idling would, and that coasting in neutral with the engine on actually uses more than just idling? If someone could explain that a bit it would be much appreciated.

Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.

Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

For modern cars engine brake means zero fuel is used.
The computer detects what is happening and cuts of the fuel.

So, if you use engine brake, zero fuel used.
If you use neutral, idling fuel is used.

Now, there are other things which get more wear from engine braking - instead of using the brake pads you use the transmission...
But after I experienced brake fading because of a long descent with high speeds and long braking before corners I really prefer engine braking and lower speeds - if someone is pushing me over the reasonable speed they can go jump from a cliff if they want.

I was lucky that I knew fading can happen in that kind of traffic so when it started I was still able to safely get off the road and stop the car - the brake did not fade completely.

I believe the confusion (and I was confused, too) is in the terminology.

"Engine braking" generally refers to using the engine to slow the car down.  I.e., downshifting.  It DOES use more fuel.  It usually (but not always) refers to manual transmissions.  I can assure you:  if you do that with a modern manual transmission, the engine will rev and you will use more gas.  I suspect it is also true of a modern automatic transmission.  If you shift from "overdrive" into L2 or L1... you'll burn more fuel.

I think the Tester is referring to a modern day automatic transmission car where the transmission is left absolutely alone in the "overdrive" selection.  Personally, I would not call this engine braking.  There is no engine braking going on.

No, it will rev but it does not use gas.
The ECU detects what is happening and cuts off the fuel injection.
I am referring to downshifting. Downshifting is engine braking for me - and for modern cars, regardless of manual or automatic it will cut off the fuel injection.

To be clear: I am only talking about wanting to slow down or driving downhill.
If you just want to coast, then of course you don't want to use the engine brake (or any brake:) ).

And about the fuel cut off: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#safe=active&q=downshift+fuel+cut+off

Spork

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Re: Hypermiling tips?
« Reply #16 on: July 12, 2016, 12:47:27 PM »
If you have a relatively modern car you should not coast downhill because it will use gas while using the engine brake doesn't.

I admit I don't know much about engine efficiency, but do you mean that engine braking uses no more gas than idling would, and that coasting in neutral with the engine on actually uses more than just idling? If someone could explain that a bit it would be much appreciated.

Whether coasting (engine on) is good or bad, depends.
- If there is only a light slope to coast down (such that coasting will put you at or below the legal and safe speed), it is good. Yes, you will burn more gas while coasting as compared to being in gear, but you will slow down less and will not have to re-accelerate as early.

Why would coasting with the engine on in neutral burn more gas than coasting in gear? Wouldn't they be pretty much the same since the engine is essentially idling, but putting it in neutral lets you coast farther?

For modern cars engine brake means zero fuel is used.
The computer detects what is happening and cuts of the fuel.

So, if you use engine brake, zero fuel used.
If you use neutral, idling fuel is used.

Now, there are other things which get more wear from engine braking - instead of using the brake pads you use the transmission...
But after I experienced brake fading because of a long descent with high speeds and long braking before corners I really prefer engine braking and lower speeds - if someone is pushing me over the reasonable speed they can go jump from a cliff if they want.

I was lucky that I knew fading can happen in that kind of traffic so when it started I was still able to safely get off the road and stop the car - the brake did not fade completely.

I believe the confusion (and I was confused, too) is in the terminology.

"Engine braking" generally refers to using the engine to slow the car down.  I.e., downshifting.  It DOES use more fuel.  It usually (but not always) refers to manual transmissions.  I can assure you:  if you do that with a modern manual transmission, the engine will rev and you will use more gas.  I suspect it is also true of a modern automatic transmission.  If you shift from "overdrive" into L2 or L1... you'll burn more fuel.

I think the Tester is referring to a modern day automatic transmission car where the transmission is left absolutely alone in the "overdrive" selection.  Personally, I would not call this engine braking.  There is no engine braking going on.

No, it will rev but it does not use gas.
The ECU detects what is happening and cuts off the fuel injection.
I am referring to downshifting. Downshifting is engine braking for me - and for modern cars, regardless of manual or automatic it will cut off the fuel injection.

To be clear: I am only talking about wanting to slow down or driving downhill.
If you just want to coast, then of course you don't want to use the engine brake (or any brake:) ).

And about the fuel cut off: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#safe=active&q=downshift+fuel+cut+off

No shit!  I learned something.