I bought a 2021 Z71 5.3L. I drove it home, all freeway, 15mpg all the way home. Had for it a couple of weeks now, 457 miles total, 13.9 avg mpg. Tire pressure 35 in the front, 33 in the rear, ride height set to normal, drive mode set to normal, 2wd selected. Not sure what I'm doing wrong but I'm not getting anywhere near the epa estimates. Anyone else see the same? Where is the 18mpg?

 

Welcome to the forum!
Is this based only on the car's computer read out, or are you recording mileage and gallons at fill ups to verify? Our 2020 (not a Z71) does 15-18mpg

 

Car's computer read

 

I see you have the Z71 package, does that mean your Tahoe has a factory lift vs a non Z71 Tahoe? I think the Z71's also come with a slightly aggressive wannabe all-terrains, maybe in a 17 inch size. IF you do have a slight lift bc of the off-road package and some type of all terrain tire, those could be factors in the lower than expected MPG.

 

I wouldn't go by the computer read out exclusively. Keep a log of miles driven and gallons used for several fill ups.

If it's lifted and/or has aggressive all terrain tires, those could be factors as well.

Son use to have a 2007 Avalanche 5.3L 4 speed. It had aggressive all terrain tires. Even with a tune up (new plugs) it always averaged 13 mpg uphill, downhill, city, highway - didn't matter.

After the rear differential failed, he traded it for a '16 Subaru WRX 2.0L Turbo 6 speed manual - 30+ mpg all day long.

 

2021 Chevrolet Tahoe 4WD (fueleconomy.gov)

 

EPA highway est. is at 55 mph. Faster you go the thirstier it will be. My '11 will get 18 on the flat under 65 mph without head winds. AFM eliminator installed BTW

 

Same issue, man. I'm up to 4000 miles. I was averaging 14.8 with mostly highway when I first bought it. Tire pressures are 35#, 2wd selected. I tried premium fuel, no effect. I upped the tire pressure to 45# and installed a K&N air filter in the factory intake housing. Now I'm at 15.1. Not sure what the issue is. And I honestly do not thrash on this truck. The $70k was quite an investment for me.

 

Update - Just took a 500mi, round trip, installed an AFe track series intake with a pro 5R filter and used 93 octane. I averaged 18.0mpg.

 

why 93 octane? less latent heat energy in it. if you don't have a boosted or high compression engine....high octane fuel is a waste. Stock class racers have proven it will slow you down.