2021 Tahoe RST Abismal mileage

[Gibby13]

Finally got some better gas mileage. Went back down to 87 gas, just did a trip to inlaws for nephews graduation and I got 15mpg on the highway with cruise set at 94.

 

[fasteddy]

94?
Do you live in Germany and drive on the autobahn?

 

[Gibby13]

94?
Do you live in Germany and drive on the autobahn?

Nope, I just stay under the excessive speed limit, which is 25+ here.

 

[89Suburban]

Auto means that the four-wheel-drive only engages when needed. It would make a slight difference possibly, but not a significant difference. Many people leave their vehicle in auto all the time. Not a factor overall....

Doesn't the front driveline stay engaged when in auto and the transfer case engages when needed?

 

[Stbentoak]

Doesn't the front driveline stay engaged when in auto and the transfer case engages when needed?

I think it’s actually the opposite. The front driveline only engages when wheel slip is detected. Otherwise it rides along not rotating....

 

[Thislife1977]

Does make a significant difference?

I’m now getting 16mi/gallon. Yukon isn’t a AWD vehicle, so the 4wd engages often even when you don’t need it like on bumpy roads or steep roads. Auto should be used when the road conditions change like a light snow/sleet/ice, gravel, bad storm...etc.

https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive

 

[Gibby13]

Finally got some better gas mileage. Went back down to 87 gas, just did a trip to inlaws for nephews graduation and I got 15mpg on the highway with cruise set at 94.

On the way back, I set cruise at 84, averaged 16.7mpg but there was a lot more traffic going that speed and drafting definitely helped.

Also both of the above are with the vehicle in 2wd, we had been in auto for the first 4000 miles we had the vehicle.

 

[Fireman591]

Finally got some better gas mileage. Went back down to 87 gas, just did a trip to inlaws for nephews graduation and I got 15mpg on the highway with cruise set at 94.

94!!!!!! I will say I hover around 20mpg at 70-75mph. Anything over that my mpg drops into the low teens. These things are like bricks and they do not do well mpg wise when above 70.

 

[Toasty]

Couple of things - the 5.3 and 6.2 have Dynamic Fuel Management, can can run on as few as 2 cylinders. There's no visual indicator on the dash to show this like previous systems. SOME half ton pickups have been built and sold with this system disabled electronically due to the microchip shortage, with $50 credit to the buyer. (Yes, it is disclosed) but this has not been done on the Tahoe/Suburban/Yukon/XL. And as for the Auto/4WD? when in Auto, the front driveline is engaged, but a very low percentage of power. If slippage is detected, greater power is sent to the wheel. So running in Auto full time will indeed impact your mileage. could be .5-1 mpg I would guess.

 

[Kpwweb]

I think it’s actually the opposite. The front driveline only engages when wheel slip is detected. Otherwise it rides along not rotating....

No. Auto engages the front axle disconnect so everything in the front turns and “drags”. Transfer case is engaged when needed, which also includes starting from a dead stop. I will get 2-3 mpg less on auto.