what gives????

[jt metal]

I currently own

 

'93 Chevy 1 ton 350 4.10 700r4..........14 mpg

'03 Tahoe 5.3 3.42 4L60e 15 mpg

'06 GMC 2500hd 6.0 4.10 4L80e 14 mpg

 

Added this rig to the mix......

 

'07 Silverado ext cab 6.0 3.73 6L90e. 11.8mpg really????

 

So a 3.73/6L90 combo, is that one to stay away from? Lol!

 

I'm not a hater! Is there something I should look for?

[patriot]

Change your driving habits?

[jt metal]

Change your driving habits?

You mean buy a Ford? 11.8 was more highway and some around town.

 

What's expected?

[intheburbs]

My 08 Burb has the exact same powertrain. It weighs 6500 lbs empty.

 

I'm a pretty severe leadfoot. I drive my truck like I stole it. The 6.0 loves to rev, and I let it. The Blackbear tune just encourages my bad behavior.

 

I get 13-14 around town, 15-16 if I use the cruise control at 65-70 on the highway.

[ColoradoDave]

2010 Sierra 2500HD, 6.0, 3.73, 6L90, manual 4x4 xfer cast, 145,000 miles, purchased used. No check engine light but scan tool showed history of the DTC being recently cleared. My first two tanks of fuel I ran through it calculated at 11.3 mpg and 11.9. I then did a full service.

 

1. Replaced severely worn original spark plugs with a fresh set of factory sprkplugs

2. engine oil changed to mobil 1 0w30 dexos,

3. tranny drained and filter changed, refilled with synthetic valvoline dex6 (old fluid looked horrible)

4., manual xfer case drained and refilled with synthetic valvoline dex6 (old fluid looked horrible)

5/ front and rear diffs drained and filled with royal purple 75w90 synthetic gear oil (old fluid looked horrible)

3. all hoses and belts changed with GM parts

 

Next tank of fuel after service showed 13.2 mpg.

 

Ran into issue with TPS/Throttle body throwing DTC's, reduced engine power, blah blah blah...

1. pulled throttle body. TB extremely filthy with carbon / oily residue...no luck cleaning it well enough to prevent DTC. replaced TB which solved DTC issue.

 

still in the 13's mpg.

 

I then reflashed computer and tranny with blackbear tune. After the flash, getting 15.5 to as high as 16 mpg. Just checked the computer and it shows 15.5 mpg in mixed city/highway driving.

 

It will be interesting to see how the fuel economy does during the winter driving season with crappy winter gas.;

[jt metal]

Nice job, C.D. !!!!!

 

Just bought truck! Looks like new wires, assuming newer plugs. You're right, I'll give this thing some love. Look into tuner.

 

Thanks, Joe

 

My avg fuel shows 13.3 but I did the math on fill up. 11.8 is what it is!!!!!

[ColoradoDave]

If you have a GPS, check your speedo vs actual. If your tires are bigger than factory and the computer hasnt been reflashed to compensate, your MPG calculations will be off because the speedo and odometer are off...could explain some of what you are seeing. Cant go wrong doing good basic service though.

[jt metal]

You called that one too. Bigger tires!

 

I'll Service all fluids with synthetic and go from there.

 

15+ is what I'd be happy with.

 

With all the gm vehicles I have, was expecting better.

[jt metal]

www.fuelly.com Cars Chevrolet

 

Went to above sight. I guess 10-12mpg is pretty normal.