anyone have bad gas mpg as me?

[70jimmy]

Or gears, or t-case. Doesn't seem like anyone cares that incorrect odometer is possibly the largest factor out there.

I figured when I went from 31's to 37's my speedo would be way off, but at the same time I went from whatever my stock gearing was, maybe 3.07 or something to 4.10, so now my speedo reads 5 mph slow at 60. Helps to keep me out of trouble.

 

[1978Blazerk5]

Some people that figure mileage after putting big tires on forget that no only is your speedo off but the odometer also. Make sure you are using road miles and not odometer if you have had a tire size change.

well I checked the speedo against the Gps and she was only 2 miles off, so i figure the odometer is pretty close

 

[onetonbb74]

With the name "onetonbb74" your mileage is expected to be bad.

def. not a DD.

 

[blazinzuk]

My blazer is 39.5 Iroks with 4.56 gears, at 65 I get around 9.5, at 70 I get 9 at 75 I get 8, faster than that I get less then 7

When I first got it stock, it got 10 mpg, put 35s on it got 10, lift 38s and 4.10s got 10

I am putting fuel injection on and hoping to get back up to the 10 mpg at 70 or 75

 

[MaxPF]

Or gears, or t-case. Doesn't seem like anyone cares that incorrect odometer is possibly the largest factor out there.

I have corrected for my gears and tire size. 10-11 MPG is my true gas mileage.

According to the sticker on my door jamb my ride came with 31x10.5x15's. The stock gears were 3.73's, and I have a 4L60 tranny (renamed 700R4, .7:1 overdrive). Using BFG All-Terrain specs gives 677 revs/mile for that tire size. So, at 65 MPH in OD in stock form the engine would turn ~1900 RPM. With 33's and 4.56's I turn 2200 RPM.

My truck isn't lifted, so any mileage vs stock is simply due to an extra 300RPM at cruise, more rolling resistance (and weight), and an ageing engine in a questionable state of maintenance (it needs to have the injectors cleaned or replaced and a new cap, rotor, wires, and plugs). It wasn't a lot better before I put on the 33's and regeared - maybe 12-13 MPG. It may have actually gotten it's rated 14-16 MPG when it was new...