Cruise control = lower MPG?

[NYRhockey23]

So, went up to Hartford, CT on Saturday night, about a 50mile drive and on my way there i got up to 75mph and set it on Cruise Ctrl. The highest it got up to was 26.1mpg then started to decrease gradually all the way down to 24.9mpg (i had reset the DIC before entering the highway). At this point, i was like "no way" so i slowed down to 65mph and set it on cruise again and the car stayed constant at around 25.5-25.7mpg. On my way back the next day, i reset the DIC again and didnt use the Cruise Ctrl and got above 27mpg going 75+.


Two things caught my attention:

1. I've gotten 30+ mpg on the highway, so these low readings came as a surprise to me, especially since i wasnt flooring it.

2. I was always under the impression that setting the car on CC would give you higher MPG.

I take it's just an outlier rather than the norm, so i'll try it out again next time i take a long trip on the highway.

[LeloSKYLANM]

My experience with cruse is like yours, I feel you do get lower mpg using cruse.

[MikeB]

Next time I'm on the highway, I'll watch the milage with cruise control. One thing I have noticed is the DIC consistantly reads about 1 MPG lower than the old fashioned calculation method.

[CdnSkyGuy]

Is it possible you were driving into the wind on the way there? I know that even a moderate wind can effect your mileage huge!

I would think that the only way you would get worse mileage with CC on would be in an automaticin a hilly area so the car is constantly downshifting/upshifting.

[NYRhockey23]

Originally Posted by CdnSkyGuy

Is it possible you were driving into the wind on the way there? I know that even a moderate wind can effect your mileage huge!

I would think that the only way you would get worse mileage with CC on would be in an automaticin a hilly area so the car is constantly downshifting/upshifting.

Well, i dont know if it was windy, nor did i know wind would affect MPG, although it does make sense since the car would have to work harder against the wind.

[BlueSkyRL]

Also temperature of air outside will affect the mileage. Colder temps = less gas mileage.

[CJsSky]

Originally Posted by CdnSkyGuy

Is it possible you were driving into the wind on the way there? I know that even a moderate wind can effect your mileage huge!

I would think that the only way you would get worse mileage with CC on would be in an automaticin a hilly area so the car is constantly downshifting/upshifting.

I travel between Austin and Dallas often. About 225 miles. I get a big
affect of wind resistance on my mileage. I try to get behind a van or
suv to improve my savings, but not to close.

[SKYtime]

This is shocking to me actually. I've always thought that cruise control IMPROVES gas mileage!

[Luke Sky Watcher]

I always get more MPG without cruise. Its always better to maintain constant pedal pressure than to let the automatic speed sensor try and maintain speed. The hillier the terrain the larger the difference. It can add up to several miles per gallon in mountain country. In addition, the higher the speed you are trying to maintain, the larger the difference. Try and maintain 70+ in hilly country and you will really cut your MPG down big time. I have proven it with a variety of vehicles. It doesnt make any difference; 4, 6, or V8. There are other factors that enter into it but with all other factors being equal, this is the case.

[CdnSkyGuy]

I get more speeding tickets without cruise...which far outweighs the extra $2 I may spend on fuel.

I'm gonna keep my cruise on

[frednorris]

Cruise control should always get you better mileage under IDENTICAL conditions. A person can not keep as steady of a foot on the gas pedal as the computer can. If you get better mileage without cruise, it's because you are paying more attention to your driving. Slower starts etc. Also, the DIC on my car has been off as much as 3mpg compared to hand calculations. Dont' believe it. It's just a guide, not gospel.

[Robotech]

I always get far better gas mileage on the way home from Pheonix than I do on the way to Pheonix. Don't know why but I do. To really test the theaory you need to do one trip under normal conditions both ways then another trip using the CC. That way you can see the result each one gives you. Even then factors like wind and weather can change the results.

[Luke Sky Watcher]

Originally Posted by frednorris

Cruise control should always get you better mileage under IDENTICAL conditions. A person can not keep as steady of a foot on the gas pedal as the computer can. If you get better mileage without cruise, it's because you are paying more attention to your driving. Slower starts etc. Also, the DIC on my car has been off as much as 3mpg compared to hand calculations. Dont' believe it. It's just a guide, not gospel.

I disagree to a point. First, if you are driving in hilly country with cruise on, just watch or actually feel the pedal depress automatically. Thats more gas to keep the set speed. With automatics it will even kick you out of overdrive - the result of both is running at a higher RPM which burns more fuel. I can drive the same route without cruise and maintain my RPMs. I might not be going quite as fast when I reach the top of the hills, but I will save fuel. Even my wife caught on to this while driving through the mountains this summer. In addition, in my opinion, the resume speed function of cruise is not efficient. A manual acceleration is more efficient. On a long highway run with not much starting and stopping, paying more attention would have little effect. Computers make life easy but they cant differentiate a hill from flatland. They are only as good as the instructions they get.
However, I will agree that in the flatlands, cruise should be the way to go and that a strong headwind can make a difference. I also agree that the DIC is a guide. On a 1800 mile trip with my Sky I recorded a difference of about 1.5 MPG. The actual fuel used according to my records hand calculated yielded the higher MPG.
As far as cruise, I guess it has a lot to do with the terrain you drive in.

[ggccg]

Originally Posted by Robotech

I always get far better gas mileage on the way home from Pheonix than I do on the way to Pheonix. Don't know why but I do.

Riverside to Phoenix is a net UP HILL drive (approx 800 ft. to approx 1100 ft.) The trip back to Riverside is net DOWN HILL.

[ggccg]

Originally Posted by Luke Sky Watcher

First, if you are driving in hilly country with cruise on, just watch or actually feel the pedal depress automatically. Thats more gas to keep the set speed. With automatics it will even kick you out of overdrive - the result of both is running at a higher RPM which burns more fuel.

I've never used the Cruise Control on my Sky, but have on our Ford 500 and Mustang (both automatics). It's very annoying how crudely they manipulate the throttle to maintain an uphill climb. They both routinely let the speed bleed off a bit and then downshift to try to regain the speed. I can easily maintain an uphill climb manually with gentle throttle pressure and avoid these inefficient downshifts.

[Sunny Ragtop]

I don't think it has anything to do with the cruise control. I think NYRHockey may have my problem...a faulty DIC (Driver Information Center)

My Average MPH speed always gets "stuck" on whatever number it happens to like. The last several days of driving it never changed from 35mph. I finally reset it today and it updates every few minutes...but soon it will get "stuck" again. So..It may not have anything to do with your actual mileage...it may just be your computer readout.

[JohnD]

Originally Posted by Sunny Ragtop

I don't think it has anything to do with the cruise control. I think NYRHockey may have my problem...a faulty DIC (Driver Information Center)

My Average MPH speed always gets "stuck" on whatever number it happens to like. The last several days of driving it never changed from 35mph. I finally reset it today and it updates every few minutes...but soon it will get "stuck" again. So..It may not have anything to do with your actual mileage...it may just be your computer readout.

I think the "getting stuck" is actually working properly. It shows the average MPG since the last reset. If you've put 3,000 miles on it and averaged 22.6 MPG, how many miles would you have to add onto the total at what fuel efficiency to get it to change even a tenth of a point? Once it settles in on a number then it is going to be very likely to stay there, and only a lot of miles that are added on at a very different average are going to impact it.

Conversely, if you reset it, now the totals are gone. If you do your first mile at 28 MPG on the freeway, and then exit and go in to the city and put on your second mile at say 20 MPG, you're going to see the average fall from 28 to 24 and update every few seconds until it reaches 24. If you add on another city mile it should then continue to fall to 23 a little slower... and so on, until you start getting a whole lot of miles in the total again, and then adding on a single mile (or portion of a mile) at 20 or 28 isn't going to upset the total average at all.

Remember, the mileage shown is the total since the last rest - not the last ten miles or anything like that.

[MidniteBlues]

Here is another subject that can be veerrryyyy controversial-I will tread lightly-However I will try to keep it simple. "IN GENERAL" And, depending on the vehicle, cruise control over all IS a fuel saver. Why? because if properly designed it will maintain the same speed it was set to. By properly design, by that I mean it will maintain throttle pressure "the same as your foot". In other words you "should not" feel gas then dis-engage, then gas then disengage--it should be a steady "engage" mode. HOWEVER, should you hit a hill, over pass, uphill/downhill incline and the "threshold" is hit, the CC will either dis-engage, engage or even drop down a gear to come back to that threshold speed that it was set at before this obstacle was encountered.> Down here in Florida we are basically veerrryyy flat, the highest thing we see down here is an over pass, or on a few occasions driving north OR south big HIGH bridges going over bodies of water, ALL my vehicles CC have worked properly on all of these occasions, that also includes the Sky's computer--I beleive that CC saves fuel, so far nothing stated here so far has changed my opinion--NO dis-respect at all intented to posters so far--Just my experience after driving these different vehicles at my old age-- I however agree with many points stated above by luke, once the CC engages IT IS very agreesive--it will want to get back to your set speed immediately, whereas if you were in "manual" mode, you can increase the speed at a lower rate, therefore saving you fuel--I guess overall there are pluss and minus for both ways-

[Luke Sky Watcher]

Originally Posted by MidniteBlues

Here is another subject that can be veerrryyyy controversial-I will tread lightly-However I will try to keep it simple. "IN GENERAL" And, depending on the vehicle, cruise control over all IS a fuel saver. Why? because if properly designed it will maintain the same speed it was set to. By properly design, by that I mean it will maintain throttle pressure "the same as your foot". In other words you "should not" feel gas then dis-engage, then gas then disengage--it should be a steady "engage" mode. HOWEVER, should you hit a hill, over pass, uphill/downhill incline and the "threshold" is hit, the CC will either dis-engage, engage or even drop down a gear to come back to that threshold speed that it was set at before this obstacle was encountered.> Down here in Florida we are basically veerrryyy flat, the highest thing we see down here is an over pass, or on a few occasions driving north OR south big HIGH bridges going over bodies of water, ALL my vehicles CC have worked properly on all of these occasions, that also includes the Sky's computer--I beleive that CC saves fuel, so far nothing stated here so far has changed my opinion--NO dis-respect at all intented to posters so far--Just my experience after driving these different vehicles at my old age-- I however agree with many points stated above by luke, once the CC engages IT IS very agreesive--it will want to get back to your set speed immediately, whereas if you were in "manual" mode, you can increase the speed at a lower rate, therefore saving you fuel--I guess overall there are pluss and minus for both ways-

I too live in Florida but our problem is not hills its traffic. Trying to maintain a speed on 75 is hazardeous at best. There are too many agressive drivers cutting in and out and you have to jam on the brakes. I take a long trip each year outside of Florida and I find it very hard to use cruise in places like western SC, NC VA and WV and PA. There are places made for CC and thats where I use it.

[Sunny Ragtop]

Originally Posted by jdigiant

I think the "getting stuck" is actually working properly. It shows the average MPG since the last reset. If you've put 3,000 miles on it and averaged 22.6 MPG, how many miles would you have to add onto the total at what fuel efficiency to get it to change even a tenth of a point? Once it settles in on a number then it is going to be very likely to stay there, and only a lot of miles that are added on at a very different average are going to impact it.

Conversely, if you reset it, now the totals are gone. If you do your first mile at 28 MPG on the freeway, and then exit and go in to the city and put on your second mile at say 20 MPG, you're going to see the average fall from 28 to 24 and update every few seconds until it reaches 24. If you add on another city mile it should then continue to fall to 23 a little slower... and so on, until you start getting a whole lot of miles in the total again, and then adding on a single mile (or portion of a mile) at 20 or 28 isn't going to upset the total average at all.

Remember, the mileage shown is the total since the last rest - not the last ten miles or anything like that.

My Average Speed in MPH gets STUCK not my MPG. This morning I was on the Interstate for almost 17 miles going over 71mph and my Average Speed never changed from 33MPH. I know that is not right.