Effect of Cruise Control on Gas Mileage

I have a 2016 Limited 4X4 with about 22K miles. I get within 1 MPG of 22 MPG on every tank and it doesn't matter if I am in town or on the highway. When on the highway I always used the cruise set to 65mph. On two trips recently, I travelled about 40 miles at 65mph without the cruise and one ended with 26mpg and one almost 29mpg! I notice that if traveling at 65 on level highway and I engage the cruise I can hear a slight sound but there is no change in the rpms. What is going on?

 

What is the sound like? Does it sound like the truck needs to upshift?

 

To answer one question, cruise control on our trucks will gun the throttle up hills if it is trying to maintain speed ... and then cut fuel going down hills as it's not needed to maintain desired speed.

Anyone who knows basic hypermiling techniques will know this is exactly the opposite of how one should drive when trying for optimal MPG.

 

No, it is a barely perceptible click and I can see the real-time gas mileage drop and stay down with no change in the RPMs. This is all on level road. I wondered if it was a disengagement of the Atkinson cycle.

 

This is on level road. I notice the real-time fuel mileage drops slightly and stays down while the RPMs stay the same.

 

Overall, you should be able to get better MPG with your own foot than with cruise control. Cruise control will always try to maintain a constant speed no matter what the road conditions. If you have a completely flat road that is fine but usually roads have slight grades to them. On an incline or hill, cruise control will burn extra gas to maintain the 65mph while most of us will sacrifice a few mph until the incline has passed.

For the 3rd generation there were issues with the shifting/transmission when using cruise control but were mostly fixed with the ecu update. That might be the odd sounds you are referring to?

 

The German in me wants to say ... "there is no such thing as level road", but I get what you are saying.

In overdrive, there can be a significant increase in fuel usage without affecting RPM's. I've stared at the throttle position sensor reading on my scangauge (and Torque app) quite a lot to learn this.

 

If you are driving normally (no race car tendencies) then cruise control will never ever get better mpg overall. Maybe for a mile or two but, over a hundred miles your foot always will do better.

 

How would the cruise Ctrl effect mileage on a manual transmission?

 

I bought a corolla a long time ago to mess around with hypermiling. 1990 5speed. Regular driving it got 36mpg combined. Hypermiling I was able to get 46-48mpg combined. That thing was a death trap though; wouldn't do that again lol.

 

I try to kick off the cruise control when approaching a hill. 3500 to maintain speed seems really excessive. Heck sometimes it's just a slight change in grade and the truck will rev up to 2500 in cruise control.

Manually controlling the throttle has yeilded better results for me but my foot does get tired on long trips in which case I'll surrrender to cruise control.

 

First time the cruise throttle RPM'd up to 5 and a half I stopped using it lol. Luckily I live in the prairies and not so much hills or mountains like on my vacation 2 months ago.

 

I just got back from a trip to BC, Canada, and I found that the best mileage was gained by using cruise control.... BUT I ran in "S" mode.... When I saw a hill coming, I'd drop the tranny to 5th and we would cruise over the hill with no real issues.... Because "I" anticipated the hill...( I saw it coming)...the freakin' CC don't "see shit"... On it's own, it waits too late and floors the pedal...(down to 4th or 3rd).. I can see the hill and drop a gear ....over we go... no problem...

I actually got up to 28.9 MPG CDN on our trip home thru the states from BC...

Just a matter of "finesse"...!!!!