3ton1/4

Boy my new 315's have killed my mileage. Maybe the auto trans has a lot to do with it. Guess you can't have good looks and good mileage. Is there any way to regain some of it, other than go to smaller tires ???

That reminds me. I need to update my sig....

Brad

jmccart

I have stock tires on my new truck. I wanted to go to 315's. I figured it would drop RPM's & net better MPG. Another guy on here just posted the same thing about interco 33's. I must be off in my thinking.
Thanx.

3ton1/4

Trust me ! The mileage comes down. I went from 19.5 with 265's to about 16.5 with the 315's. I haven't but the pencile to it yet but I can tell from the number of miles I'm now getting from a tank. If you have the six speed manual it probably won't be as bad.

jmccart

Zowie! That is a big drop.
Thanx.

jmccart

I have read on here a few times that ya' want to keep it under 2100 RPM''s for good milaege. Right now with the G56/3.73's, I am cruising on the fwy at like 2400.

Beavermike

I assume this is had calculated?
If you use the overhead, of course you will need to reflash. I don't think I noticed much of a change going to 285s, maybe a few tenths. But then 315s are way bigger.

3ton1/4

Not going by the overhead. After I installed my chip the overhead is wayyyy off.
I hand caluclated the 19.5 with the 265's. I have just seen my average tank mileage drop from around 550 to 450 miles. Granted that not running it completely dry. Next time I fill up I will hand figure it with the 315's.

Don't get me wrong. I love the look ! I may look at some more mods later on to try and regain some mileage.

XLR8R

My mileage is better with the BFG 315s - it lowers the cruising RPM... the new 37" Toyos should help even more.

bullocklabs

My mileage is horrible on my new 06 I am running a 4.5" lift with 35x12.50 Toyo MT's. I have only filled up once so far but I only averaged 9.5 mpg. This second tank so far seems to be going just as fast as the first one did.

TX_Diesel

With a 6-spd going to a larger tire should help to a certain extent. Once you start lifting the truck and adding wider/larger tires then it will have an adverse effect because of the weight, drag, etc. the new tires/lift put on the truck.

I think 315's with a 2" level is about as big as you can go without starting to see a decrese, of course this is also on a 6-spd, due to the gear ratios when adding this combo to the auto it will change the shift points and what not which will drop your mileage.

Speed Shift

A buddy of mine lost 3mpg when he went to 33s on a NV5600. I plan on doing the same with mine and see if the ratio is better for the G56 ...... I'll let ya know....

marc03

If that continues you got some probs. With basicly the same size lift and tire size I get about 15-16 mpg.

jmccart

Hey Speedshift. I just got a G56 truck with stock size tires. My last truck had the NVG5600 & 285 tires. With the smaller tire & lower overdrive of the G56 & really notice a RPM diff. on the fwy.

Raspy

It's not just the gear ratio that affects mileage. Yes, bigger tires slow the engine but bigger tires, and especially, heavy off road tires, add a lot of drag. They are a lot more massive and have more wind resistance. All that equals lower mileage. So there may be a slight gain in mileage from the RPM drop but there is a larger drop in mileage from the added drag of a much larger, wider and heavier tire. It's not just the RPM of the engine that counts, it's the power the engine must make to propel the truck down the highway. Power is different then RPM.

My mileage went down by about 1-1.5 mpg whenI went to 315s.

If you want to correct the gear ratio problem, and you want to do it with tires, get an 85 series radial with highway tread.

If you want serious off road performance or that kind of look, be ready to pay the price with lower mileage.

Wetspirit

Speed Shift

Yup, it might do 2400rpm @ 70mph but dont plan on slowing it down!!