Cruise control...gas saver, or gas waster?

[mjncad]

I have a 1999 F-250 4x4 extended cab, long bed with a V-10, 5-speed manual, and 4.11 limited slip rear end. I average between 13 - 13.5 MPG with it.

I'm not a fan of cruise control; but I decided to try it for a couple of tanks of gas, and it seemed to actually lower the MPG instead of raising it. My mileage dropped about 0.5 - 1 MPG.

My thought is that cruise control would raise mileage by keeping the speed more constant than I can with the gas pedal. But after my experiment, I'm theorizing that the constant micro adjustments CC makes to the throttle to maintain a set speed actually lowers the MPG.

Any thoughts on the theory? I went back to driving the truck without using CC.

 

[Gale Hawkins]

mjncad as you have seen the use of cruise control can cost you mileage. Your logic as to why is along the same lines as mine.:thumbsup:

After years of driving your foot is connected to your eye/ear input so you have a built in cruise control especially on roads not totally flat.

The cruise on the truck gets no input into what is going to happen in the future and this bites hard in the hills.

 

[MikeD74T]

Agree : Cruise control is less fuel efficient because it works harder to maintain speed up hills and holds you back on the downhills. Cruise is purely reactive & doesn't anticipate anything therefore utilizes excessive throttle modulation.
I use it extensively as the minor loss of milage is worth the convenience of not getting a speeding ticket ( I have a lead foot). You can learn a lot about your & other's driving habits by using cruise. e.i. I set mine about 70-72 on 65 mph highways. It's amazing how many people speed up as you catch up with them then slow significantly after you get a couple lengths beyond. Another thing most people do is drop about 3-5 mph at the crest of a hill when assending. Very few drivers in NH maintain a speed that varies less then 5 mph depending on terrain & traffic. I'm more aware of what's around me on cruise because if you don't pay attention to your mirrors you'll get boxed in behind slower vehicles because someone will start to pass you then slow down until you drive up on slower traffic in your lane and have to brake. MikeD74T

 

[Bird]

Everything I've ever read, as well as my own experience, is that over 90% of drivers will get better mileage with the cruise control. But yes, it is possible to get very slightly better mileage without it, if you know how, but to do it you have to be frequently changing speeds and making a real nuisance of yourself if there's any other traffic (as described pretty well by MikeD74T). It's amazing to me how many idiots very slowly enter a freeway, causing traffic already there to slow down. Then the same idiots will very gradually speed up to 10 mph over the limit. Then they slow down going uphill, causing other traffic behind them to slow down, then speed up going downhill so traffic behind them can't pass.

But just for the sheer convenience of it, I hope to never own another vehicle without cruise control.:laughing: I probably use mine as much as, if not more than, anyone. When I go to the grocery store 2 miles down the Interstate, I just stay on the service road, speed limit of 45 mph, and use the cruise control. And of course, like Mike, I have to be careful to avoid going too fast without it.

 

[JasG]

I have noticed when your speed drops, on any vehicle I have tried cruise control. It hits the throttle harder to get back to the set speed. This even on flat ground where I tend to hit the throttle a little less harsh to get back to speed.

I do use it sometimes just so as Mike said not to get a ticket. On long trips is is easy to over time pick up the pace a little too much and not realize it. It is funny to as he said the number of people who speed up when you come up on them. Or better yet pass you then slow down 3-5 MPH.

 

[Bird]

I have noticed when your speed drops, on any vehicle I have tried cruise control. It hits the throttle harder to get back to the set speed.

That can certainly happen. It's even normal, I think, if you've allowed the speed to drop too much before hitting the "resume".

But another thing I like about cruise control is the speed with which it reacts. We bought a new 1993 Ford Escort station wagon with a manual 5-speed transmission to tow behind a motorhome. With that small engine, if you were not using cruise control when the air-conditioner compressor came on, you'd feel the sudden load and slight slowing, but if the cruise control were engaged, you'd never feel a thing.

Anyway, I can understand some not liking it. In fact, I'm not sure my wife has ever used the cruise control.:laughing: I don't think she has.

 

[Toyboy]

I use mine a lot also on highways. I'll set it say... 64 to 68 (limit is 70) sit back and let "the pack" blow on by. Next thing I know I'm all alone again on the road. I used to be one of those that ran w/the pack but I guess I'm just not that much in a hurry anymore. Don't have to worry about cops either. Your mention of the slow pokes merging on the interstates drive me nuts too. They will merge on at 40 making everyone get out of their way, and the next thing you know their blowing by you.

 

[dodge man]

You will get better gas mileage without the cruise, but who wants to concentrate that much. If you use more of a constant thottle approach instead of a constant speed approach but that has a way of annoying other drivers by your speed being all over the place.

 

[Gale Hawkins]

Sometimes in the old 454 motorhome with the 4L80-e transmission I use cruise but keep it out of OD if there is much locking and unlocking of the torque converter and especially if it is coming out of OD at least once every mile.

In OD with cruise on it will drop about 5 MPH before dropping back to 3rd and unlocking the TC. Then it goes to wide open throttle (WOT) trying to get back to the set speed but on much of a hill it never does until the top.

Out of OD the speed loss is much less and even the TC often stays locked much longer even if it does finally unlock. TC unlocking jumps our RPM by 200 but at the same gound speed.

For the days of weak overloaded truck driving I will gain some speed down for the next hill. Cruise can not see ahead.

At WOT and still no pick up in speed is a BIG waste of gas in my view.

Like others I will give up 1 MPH on a long trip to have cruise however there are times when cruise may increase MPG without question. Two lane roads with hills I do not use OD or cruise for better power/fuel ratios. Staying the right power band is more important to me than MPG.

 

[FlaDon]

Sometimes in the old 454 motorhome with the 4L80-e transmission I use cruise but keep it out of OD if there is much locking and unlocking of the torque converter and especially if it is coming out of OD at least once every mile.

In OD with cruise on it will drop about 5 MPH before dropping back to 3rd and unlocking the TC. Then it goes to wide open throttle (WOT) trying to get back to the set speed but on much of a hill it never does until the top.

Out of OD the speed loss is much less and even the TC often stays locked much longer even if it does finally unlock. TC unlocking jumps our RPM by 200 but at the same gound speed.

For the days of weak overloaded truck driving I will gain some speed down for the next hill. Cruise can not see ahead.

At WOT and still no pick up in speed is a BIG waste of gas in my view.

Like others I will give up 1 MPH on a long trip to have cruise however there are times when cruise may increase MPG without question. Two lane roads with hills I do not use OD or cruise for better power/fuel ratios. Staying the right power band is more important to me than MPG.

A lot of that has to do with the tranny and your gearing. If that was a T-1000 in there you'd drop down one gear and go. The TC in my truck causes a 400 RPM change in 4th. It's like having another gear. Our old MH had a 454 but only a 3-spd tranny. It would take the same grade in 3 without changing gears. But the fan sure would get loud.