fuel mileage

[ms2335]

I have a 72 that will be running a 5.3 with 295/45/20 tires on the back, when I am done with restro. What kind of mileage is the 5.3 liter guys getting? What gear ratio are you running? I am hoping to get in the 18-20 range will that be possible?

[glock35ipsc]

I'm getting a consistent 18-19 in town, and 20-21 on the highway.

I run 3.42 gears and a 28" diameter tire. You would need about a 4.11 gear to turn the same RPM @ 75 mph.

[ms2335]

I do have a 4.11 rear end right now but was thinking that was to low for mileage the reason I was asking. I have a 4L60 transmission also.

[TR65]

Glock,

I don't get your math, the 295/45-20 is only ~31 in. diameter.



MS2335,

I get 18-20 back and forth to work with a 6.0 L LS2 and I am working on getting it over 20. I think the key is getting the high gear RPM< as low as possible. I am running 1800 at 70 mph in my 65 (3.73 gears with 2:1 overdrive in 6th). I run the exact same gearing in my LS3 Vette and get 22 mpg on the same route. The difference is mainly aerodynamics as near as I can figure. Our trucks have at least 4 times more drag than the Vette.

TR

[glock35ipsc]

Originally Posted by TR65

Glock,

I don't get your math, the 295/45-20 is only ~31 in. diameter.

Which math?

My tire is 28", and with the 3.42 gear I'm turning about 2200 rpm at 75 mph.

According to my trans/gear/tire calculator, his 295/40-20 would need to run a 4.11 gear to achieve a similar rpm @ 75 mph.

That is, of course, is from memory (which is sketchy at best ). My spreadsheet is on my puter at work, so I don't have access to it right now.