Cruise Control Gas Milage 2021

I recently road-tripped from Wisconsin to Wyoming and was absolutely shocked at my gas mileage. I was under the impression that highway driving in cruise control would give me an increase in MPG. This was not the case at all.

I have a 2021 TRD Sport, Automatic, Longbed.

All I have done is put new tires on it (Cooper AT). The truck is absolutely stock otherwise.

On the way out west, my MPG displayed at 12.6 by the time I finished the drive. This was using cruise control the entire time. I do understand that once you get 70+ in a truck that mpg is always going to go to shit. But for a mostly stock truck I thought this was a little ridiculous.

Oddly, once I got to the mountains I stopped using cruise control and the mpg went back up to 18ish. Now, this is driving through mountain passes and some flats which I was expecting to be the worst contributor to mpg. Then, on the way back, I didn't use cruise control and still was at around 17.

WHY DID CRUISE CONTROL WASTE SOOOOOO MUCH GAS?! Makes me never want to use cruise control again.

 

How fast were you going when you set the cruise control? Also, were you using standard cruise control, or that adaptive cruise control shit?

 

Questions

What was your speed set at?
What tires do you have (size and load rating)?

Wind also plays a major role. I recently made a trip from Nashville to Atlanta. I averaged 19.8 going to Atlanta but only 15 on the return trip. The only difference being ambient temps and head wind.

 

3 main speeds were 60, 70, and stretches of 80.

I should also note... say I'm going 70... I would set the cruise, the truck would be going 69, it would rev up to 70, it would stay at like 3500 RPM long after it reaches 70, and it would NOT regulate the RPMs back down to around or under 2k. However, if I would go 80 without cruise control, I could manually rev to 80, find a sweet spot in the pedal, and be going 80 at like 2k RPMs. I could not believe how long cruise control took to down-regulate the RPMs.

 

Read my previous reply for speeds. I do NOT have E load tires, I went with SL for the very goal of better MPGs. They are 265/75/16.

 

This morning I drove to work. It's an 18.9 mile commute one way. For most of that drive, I'm able to set the cruise control @ 65mph. Usually on my LCD screen it shows "19.8" or higher as my MPG. But there was a strong wind blowing today, and it read "18.9".

When I pulled into work and stopped the truck, the LCD read out changed and read "21.4MPG" for the trip I made.

It's important to realize that the there is OVERALL MPG's, and the MPG's you got for a specific trip.

 

On that note - I always use standard...Why would I want to be at the mercy of the idiot in front of me - who is most likely NOT using cruise...?

 

Best to avoid using adaptive cruise in hilly areas. Great for level, low traffic highways...if there is such a thing.

 

Noted. I do get defaulted to adaptive, however, there was almost no traffic on the way out so it wasn't kicking in.. Unless being in adaptive, even with no traffic, acts differently than normal cruise.

I will turn that BS off from now on.

 

Doesn't matter, both have shitty throttle control.

Y'all hitting the nails on the head. The transmission has two overdrive gears, 5 and 6. It will drop down into 4th to get up to speed quite a bit. But only when in cruise. I can have my cruise on and it will drop to 4th sometimes 3rd on a hill going up, but if I don't use cruise, the same hill I can gain speed and keep it in 5th or 6th. Throttle control from cruise is a huge disaster, the transmission shift points are a part of that but I think Toyota really bungled it with the cruise control on this thing.

I have a 2020 with the new ECT flash for the transmission. Same shenanigans.

Truck drives great when it's under my control. Cruise blows. Which is fine around town but a 7500 mile road trip can get old, quick.

Kansas.


Edit: Adaptive may actually be even better, if I leave the addaptive on and tag in behind an 18 wheeler on hills, they usually slow down and I stick in 5th or 6th for the hills. I went out the mass pike behind big rigs the whole way and used cruise for almost all of it. No big deal.

 

These trucks just hate 70 is what I think. If I go low to mid 60's on cruise, I get above 20 mpg all day long.

Had to follow a friend for 2 hours once, he kept a cool pace of 90 mph. My truck got a few mpg better at 90 than 75.

 

That’s just wild to me! How shitty that this is a thing. Especially considering highways around me are all 70 and people do 80

 

It is super frustrating when the cruise control system wont properly shift into a higher gear and seems stuck at high rpms for no reason. The adaptive cruise is bad about that.

Pro tip, when it does this, you can tap the gas pedal and the truck will shift into a higher gear.

 

Ill second this. Right at 70, these trucks are terrible. Its just a bad spot for their drivetrain combo. I've found that setting my cruise at 72 will give me much better results compared to 70. Being on larger tires, that puts me at about 74.5mph on the GPS.

 

On this note, I put my truck in S6 every time I use constant speed cruise now. It will still shift down into 5th and 4th, but will shift back up very quickly, normally only takes a couple seconds.

 

I don't know where you got the idea that cruise control gets better mileage. It is absolutely false. It is not as efficient as your foot.
I would think headwinds played a major part on your way out.
Lastly, your truck's most efficient speed is only 50 mph. Here's a typical curve. Take a look at the amount of HP required to go from 50-70 mph! All of that is wind resistance. Even a 5mph headwind is additive and will suck the fuel required.

 

Relative to me driving in the city and short stretches of highway, I would have expected a cross country trip in cruise to perform better than constant acceleration and stopping.

 

I have the same tires as you OP, and I get the same crap mpg if I use cruise anytime I have a headwind or if I hit annoying gradual hills that cause the truck to rev. I get the best mpg if I just use my foot unless, like stated above, I'm on long flat stretches. I can say though adding the Cooper ATs took off a couple of mpg compared to the stock Firestones, so keep that in mind as well.

 

Elevation plays a factor as well. You essentially drove uphill across half the country on your trip out. In addition your engine became less efficient and was making about 50hp less by the time you got to Wyoming.

 

I agree, and totally expected the slight drop. I was just shocked to see the number 12 when looking at the MPG. I’ve heard of lifted, 33” tires, loaded bed rack rigs getting this much.