Mike Johnson

I have a 2WD 2013 with EcoBoost and a 3:31 rear end with factory transmission cooler. I pull a 6,000# travel trailer. I only get between 7.5 and 8.5 MPG when towing. Will changing to a 3:73 rear end improve my gas mileage when towing?

frieed

They will help you move off the line quicker and pull the hills in a higher gear, but are not likely to help gas mileage.
If you want better economy when towing, slow down. Power required goes up exponentially with the speed. e.g. 2x speed takes 4x the power and linearly with the frontal area of the trailer. e.g. 2x frontal area takes 2x the power.
The frontal area of your trailer is fixed, the speed is not, just slow down or get to know the gas pump.

JLTD

frieed is right....but I have also heard that in some cases the better ratio can allow the engine to not work as hard so you may use less boost. But, YMMV (your mileage may vary).

If you look at it from a $$ perspective, it's going to be more than $1000 to have the work done, at a chance to increase your mpg, to what, 10 while towing? At that rate it would take a very long time to make the cost worthwhile...and there's no guarantee.

clearnetedm

I agree with the others here. For what it's worth I have 3.73 gears and tow a 6500lbs trailer and get the same mileage as you. I know there are many variables between our trailers but it's unlikely to net you much in gains. Plus as mentioned the cost would never be recovered unless you can do it for free or close to.

atwowheelguy

Can't tell how yours would change, but my '13 EcoBoost 2WD 3.55 towing a 27.5 ft., 6700# loaded toy hauler gets 11.6-12.3 mpg @ 55-60 mph. How fast are you towing?

brulaz

That's horrible mileage. I get 10mpgUS pulling the rig in my signature on Reg gas (10.7 mpgUS on Premium) at 55-65 mph.

Agree with the others, "speed kills" ... your mileage in this case.

Norotso

You can scroll back and check my fuel stats for the past couple of summers. 3:73 gearing, and tow at 65mph or 105kph

JLTD

+1; Wind resistance rises rapidly above 55mph. At 75 I see 15mpg or less, at 60 it has been up to 22mpg.

Mike Johnson

My 7.5mpg is at around 70MPH. If I tow at 55 I get closer to 9.5 to 10.

olgzr

You can lock out 6th gear and see if the mileage improves. If it does, steeper gears might help.