Hey fellas !

Two days ago, i went with my brother to buy a bur for him.

I have 2007 LT with 4 spd tranny and 22'' rims with 305/45 tires.
He get 2009 LT with 6 spd and factory rims and tires

we were cruising in speed 70 mph for 200 miles long trip.

My avg was 18.1 MPG
He was getting 21.4 MPG

so, this is the different btw 6 spd tranny and big tires.

 

Well first of all.....your gonna get worse gas mileage cause your tires are almost 4% taller then stock. You probably got 18.7 mpg with the difference.

 

And second of all......I doubt he got 21.4 MPG at 70 MPH which beats the EPA rating of 20 and at lower speeds.

 

Also the heavier wheel/tire combo will probably lower the mpg somewhat.

 

And of course you should hand calculate to verify the accuracy for a few tanks
but 21 does sound high but not necessarily unreasonable.

Were you following each other closely and who was in the lead?

The following vehicle can get worse mpg because you are trying to maintain a distance to a particular vehicle meaning the following vehicle is slowing and speeding up more...

 

I once was getting 22 mpg at 70 mph for a ten mile stretch due to a brisk tail wind. It was actually in V4 mode part of the time.

Bottom line, there are a lot of conditions that factor in to mpg.

 

is yours 4x4?
over a 200 mile trip going 70mph I get basically right at 20mpg hand calculated (more or less depending on any wind)
ours is 2 wd

 

the trailing vehicle will get better MPG (check mythbusters for proof).

Also, highway is easy on these rigs, they don't actually have much more drag than a prius!

it's city that kills it...

also, just use the dash MPG... if you trust the tach, oil, temp, speedo, odo, air temp, a/c temp, fuel, voltage, compass, gps, air bag sensors, seat belt sensor, etc, you might as well just trust ONE MORE GUAGE.

 

That is only if you are following a bigger vehicle (tractor trailer) and you have to tailgate a bit but your right it does work
Its been my exp when in vehicle convoys the followers tend to spend a lot of time slowing and speeding up to keep the gap closed...
But as shark stated there are many variables to consider..

 

Personally I don't trust any of the gauges to be accurate, especially the mpg. Every GM vehicle that I've owned w/ the mpg function has consistently been off by 0.5-1.2 mpg.

As a GM guy once told me, these are not gauges, they're indicators. They make no claim to accuracy.

I've noticed that when passing a big rig, the mpg goes up when you're along side the drive wheels. I attributed it to a "bow wave" effect but might be something else. Following behind one closely definitely helps but tends to pi55 of the trucker cuz they can't see you.

CDs: Hybrid=.34, LTZ=.36, Z71=.38, Corvette=.29

What's it for a Prius?