Another 2 ?s regarding maximizing gas mileage

Is cruse control more efficient than trying to maintain speed manually :slight_smile: I mean by foot? Is there a word comparable for foot as for hand?

Second question: While in cruse control going up a hill would it be more efficient to bump the speed down going up and bump it up while going down the hill?

In my unscientific observations of driving styles and mileaage over the several years and miles in many vehicles it would seem that holding the accelerator at a fixed position and allowing the vehicle to benefit from going down hills by gaining speed, and still holding the pedal constant, allow for the loss of speed climbing inclines that follow. With many years driving 300+ miles daily in a 1/2 ton van, I was able to average nearly 19 mpg over hundreds of thousands of miles. I never did any comparisons other than my mileage versus other drivers in near identical trucks. Most could not surpass 16mpg.

You are essentially asking a single question.

To those who wish to attain maximum mpg on the highway, it is likely that you would achieve it without cruise control and do so in the manner you describe; that is, give up speed when ascending and reclaim it on the downhill run. I acually tested this idea years ago when I installed a driving computer on my '84 Buick.

Of course, attaining maximum mpg need not be everyone’s concern. On my solo runs to NYC, an 11.5 hour trip, I could not handle the stress of constantly feathering the accelerator pedal the entire trip. Fatigue sets in. That’s why I turn things over to the cruise control.

I’ve found cruise control delivers up to 5% decreased fuel consumption.

I suppose changing the speed slightly while going up hills can offer some improved mileage, so long as you actually do bump the speed back up when going down the hill. However, I think it’d make a difference of at most 1% better mileage, hardly worth it. You could get better mileage improvements by chance.

I make the same 500 round trip on the PA Turnpike once or twice each month. I’ve driven it using cruise control and I’ve driven it without cruise control, many times each, and I have been unable to detect a difference in fuel mileage between the two. After much experimentation, I now use the cruise control as long as traffic and weather conditions permit.

The biggest impact on fuel mileage has been vehicle speed. It takes a lot more fuel to travel at 75 mph (the speed I try to maintain) than it does to go 65. The second largest impact has been the weather. Rain and wind (especially a head wind) will reduce fuel mileage. A nice tail wind will increase mpg slightly.

If you use the cruise control, I recommend you “set it and forget it.” Adjusting the speed every time you climb a hill will probably use more gas than maintaining a constant speed.

The answer to each question is both yes and no.

It all depends. If you are skilled and drive well, you can beat the cruse.  Many people would loose out doing it manually.  Same for the hill deal, it depends on the car, the hill the design of the cruse etc.  The difference is usually small for both of those situations.

This reminds me of a Roxette song. “The answers are so simple, but the explanations are very hard to do.” I don’t remember the name of the song. They have a lot of good catch phrases like that.

“Go to Sleep”, from the Crash! Boom! Bang! album.

…There are tears without the colour
A million seas with water
An ocean full of people where shattered hearts can go.

And love’s a golden ripple where answers are so simple
But the explanations are very hard to do. …

Nice to see a classic band quoted on here!! We need more of that.

I think “you’ve been thunderstruck” would apply to a lot of the posts we get here.

I suspect you can obtain better mileage by manually varying your speed as you go u[ and down hills. However, I prefer to use the cruise control and maintain a constant speed (probably safer in traffic and certainly easier).

You most certainly will use less fuel if you let your car slow down up hills and then let gravity give you back your cruising speed when you go back down the hills, but, doing this also significantly lowers your average speed. If you compensate for the time you lost slowing down on the hill with a higher cruising speed, there goes all the fuel you saved on the hills.
If a lower average speed is acceptable, then I think it would be more efficiently accomplished by driving at a lower steady cruising speed.

Don’t underestimate how much slowing down impacts your moving average. The reason that interstate highways get you there faster than old fashioned highways has a lot more to do with the fact that interstates have no stop lights or 30 mph speed zones than it has to do with high speed limits. Stop to pee at a gas station, and there goes that slowpoke you passed a half hour ago and you have to pass him all over again.

While holding your foot steady regardlessof how much your speed wanders may get better mileage, in mountainous areas you’ll drive the people behind you nuts. Your may encounter road rage, or at least people fighting to pass you at the earliest opportunity…even taking risks to do so. Unless you live in the plains states where your speed won’t vary much and traffic is almost nonexistant.

Right or wrong, that’s the reality. I do not recommend this practice.

If you have automatic trans I suspect cruise control will win mpg unless the hills are very steep and you sense the trans having to go two gears lower than overdrive to maintain speed. Then manually slower speed only 1 gear below O.D. would be better mpg. Automatics coast down hill pretty efficiently.

If you have standard trans than turning off cruise and shifting to neutral down hill will save gas but becareful about going faster than you can stop. With standard trans you need to watch your rpm that you’re not getting too low going uphill. Most cruise controls will shut themself off and idle when the rpm gets too low. Then you need to manually down shift and manually get on the accelerator.

If you use cruise control to go the speed limit instead of going 10 MPH or more over if you let your foot do the talking, you would increase mileage.