MarshalTex

I have not read much on the mileage of an EB with the 3.15 gear. It would seem with the low rpm torque of the EB, it might get be able to get better mileage with the highway gear. Most people have the 3.55 or 3.73 gear and report low 20's when trying to get their best mpg. On one forum, it was reported by an op with an 3.15 that he could get 24-26 when driving on level ground at about 65. Sometimes he found he could get as high as 28 when driving around 60. Has anyone else seen this? I am interested in high mpg and not heavy tow capability.

engineermike

I'd say that's pretty accurate. My 3.15 supercrew is getting 27 mpg at a constant 65 mph and 28+ at 60. I've achieved 24.5 mpg over a 250 mile insterstate trip also. All this was on E10, so I would expect 1-1.5 mpg better on pure gas.

Twisty

27 and 28+!! That is great!!

MarshalTex

It just seems that with the 3.15 you make the overall best use of the torque. I think if more people new of the possibility of outstanding mileage, the sales of the highway gear would go up. Does the high gearing affect city driving and lug the engine? How about towing with the 3.15?

engineermike

Most people don't seem to realize or appreciate the effects of the extremely short gearing in the new 6R80 transmission. The 3.15 rear gear with the 6R80 is the same overall ratio as a 4.50 rear gear with the old 4R70W trans. So no, it doesn't lug the engine at all, even when towing.

slowmoving1

2011 Super crew 2wd
3.5 eco boost
3.15 gears
1400 miles on trip B average MPG 20.9
This tank 21.7 mpg

55-65 mph it will avg 23-25 mpg

Also I towed 3500 pounds the other day 18.9 mpg going 70-80 mph no lugging issues towed great

bubbabud

Same numbers exactly except trip B was for 9100 miles and have limmeted towing 6000 lbs with standard tow package no isues 2011 xlt scab

MarshalTex

You guys are proving what I was suspecting. At very low rpm, the engine is making more torque than alot of gas motors are at high rpm. With the right transmission gearing and the right gear. You have the best of both worlds. I am puzzled why more trucks are not being equipped with 3.15's and are reporting great gas mileage. I am suspicious that the dealers are auto ordering 3.55 and 3.73 due to old habits and then most are just buying what is on the lot. I am fixing to have to order a '12 because I can't find what I want on the lot. I rarely tow and make alot of very short commutes, but I at least want the great mpg on the highway.

DieselDawg

at 65 mph in Texas flat ground with 3.55's...23-25 is possible. With 3.15s I could believe 26-28 due to torque

jcain

as long as you keep the turbos unloaded, you're essentially driving a 3.5L v6 with 10:1 compression