I still don't know how. Your running smaller rear gear, smaller engine, but a manual. See comment to tsduke.

OP & slowride, like tsduke, I was at 14.6 MPG thruout winter. This after my efans install. Which I keep hearing is due to winter gas. My tune isn't up to date by someone who can tune better than me for the 160* stat (which may come out if 14.6 continues but not sure). I was gonna yank cooler stat cause b4 fans & stat, it'd get 16.6-17.1 mixed w/. a best of 18.1 (babying). The 16.6-17.1 was heavy foot or not, it varied little. But now, in winter, 14.6 seems the norm.

Oh ya, now there's a 110# cover on it, it might help aero, which should help MPGs but it's weight might make it a wash. Jury still out on Snugtop helpin MPGs, at least in my case thus far.

FWIW, yesterday's fill-up, if I did it accurate, 17MPG mixed.
I'm hopin it's right, cause either gas blend changed, I calculated wrong or my hope, it improved. I'm hoping it improved but how, I don't care cause I changed nothing.

trxmxzx is the 16-17mpg avg in your 99 ecsb 2wd w/. mods in sig HWY or cty or mixed?

 

GMT900 RCSB 5.3 w/AFM 3.73, Intake, tune 18.0 mpg.

 

13 city/17 highway with the stock 60 and stock stall

16-17 highway with the 80 and Yank stall, city I'm not sure, but with similar driving I'd expect mileage to go down to maybe 11-12.

 

If I actually calculated mine, I'd probably shoot myself.

 

Scott, I guess u don't need that 1st gun then.

 

22 highway and 16-17 around town on 35's




Its my Duramax though LOL.



Im wandering how much MPG i'll lose going from the 5.3 to the 6.0 .?

 

i get 15.5 in city
17 on the highway

 

13-15 in town, 19-20 on the highway.

 

454tbi/turbo400 It averaged 10 on a 1000 mile trip at 80/85 mph. but only does 6-7 around town. Hopefully the 5.3 swap will be done in the next few weeks. Jay

 

Last long drive (700) miles unloaded, 23.5 (With lean cruise set to around 16.5)

Around town i get about 14-15 cuz i drive like an *******.