Seems some folks here get 18+ MPG driving 75+ MPH,No way will my 04 yukon do that.Just got back from a family vacation.The first leg of the trip driving 57-63 (about)MPH,going over a mountain pass we got 19.2MPG,the rest of the trip consisted of a lot of freeway driving crusing 70-77MPH,mileage varied on several tanks but it looks to have averaged around 16.

Just wondering how some folks here get great mileage at speeds?

5.3,4x4,3.73s,westers tune,borla catback.

 

I got 18 in my moms hoe 2wd 2000 running a little over 70 with flat land and 4 people with one of those shells on the roof to hold all our crap going to FL. It has a k&n drop in and thats it. I just dont see 18+ happening running that fast my buddy has a rcsb 4.8L and he doesnt even get that with exhaust and intake so I would raise the bs flag on a thaoe getting 18+ runnin 80 mph.

 

The best I have seen out of my ECSB is 21.7 mpg. This was driving at night with cruise set just under 70. This was a 250 mile trip; hand calculated mileage. edit: I also have 3.42 gears.

 

Huge difference in mileage for me when when crusing @ 1800 RPMs VS 2300 RPMs

 

Oh yeah I think the tahoe has 3.42s cause it has no off the line performance at all.

 

I average 19.1 mpg on highway with the cruise control set on 78mph. Drivin in the city I average 16.8 - 17.0 This was what the info center shows on my truck and it was also hand calculated to verify.

 

I got 19.4 mpg out of my RCSB truck once. I was and shocked. I had intake, true duals, 3.42s, and 20s on the truck. I was cruising at about 75-80 mph on I-45, but that was at best. I usually get close to 16 mpg on average in the city and around 17 on the highway.

 

I get 15 in the city on my ECSB 5.3 and about 15.5 on the highway running between 80-85 and at some points I do put the pedal to the floor just for kicks and giggles

 

I'm averaging about 18.5-19 mpg running at 70 mph on the freeways back and forth to work. Much faster and the mpg drops slightly, but still not too bad.

Going from stock 3.42's to 3.90's I saw a bit of a mpg drop, but then gained right back up with the insertion of my cam and headers.

 

My SS does the same thing as your truck, 55-60mph I can get 18-19mpg but then if I get on the highway and set the cruise at 75mph goes down to 15-16mpg. It has to be the 4.10's, well and the fact that my beast weighs about 5,300 pounds with me in it.