Tow/Haul Helps Fuel Mileage

[Brocky]

I finally got a chance to test it out in my signature truck.Exhaust brake always in position one. Last winter I had a 1300 mile tankfull: 30% Interstate, 60% local 2 lane roads, and 10% city. Running a normal empty (10000 lbs) without tow/haul and got 16.3 MPG overall. This past weekend I made a similiar percentage of roads, 1100 mile trip up to Ohio and back, running all back roads in Kentucky and Ohio and used tow haul most of the time and got 19.4 MPG overall. The only thing is slightly rougher down shifting and when using the brake pedal to knock off the cruise it wants to drop 2 gears at once, like from 6th to 4th, but if you keep a little on the throttle and use your left toe on the brake it does not do it..

 

[gsbrockman]

I *think* your numbers are skewed due to the fact you were running winter blended fuel for your first calculation.

 

[Bob4x4]

I finally got a chance to test it out in my signature truck.Exhaust brake always in position one. Last winter I had a 1300 mile tankfull: 30% Interstate, 60% local 2 lane roads, and 10% city. Running a normal empty (10000 lbs) without tow/haul and got 16.3 MPG overall. This past weekend I made a similiar percentage of roads, 1100 mile trip up to Ohio and back, running all back roads in Kentucky and Ohio and used tow haul most of the time and got 19.4 MPG overall. The only thing is slightly rougher down shifting and when using the brake pedal to knock off the cruise it wants to drop 2 gears at once, like from 6th to 4th, but if you keep a little on the throttle and use your left toe on the brake it does not do it..

use the cancel button to shut the cruise off

 

[Brocky]

This was all on South Carolina fuel.. They do not know what winter is down here..

 

[gsbrockman]

This was all on South Carolina fuel.. They do not know what winter is down here..

Scroll through this document (towards the US Maps, and especially Table X5.1) and you'll see even southern fuel is blended some, although not to the degree that ME, MI, ND, MN, & MT are blended to in the dead of winter. I'd be hard-pressed to think that more aggressive & frequent downshifting (ie TOW/HAUL engaged) nets better fuel economy than with it off (ie coasting, either with zero exhaust brake, exhaust brake full on, or exhaust brake on AUTO).

 

[Newsa]

I know some have reported better fuel mileage after truck breaks in. Others have reported that their truck just seems to pull better (and burn diesel more efficiently) when it runs at 210+°F. I think I have also noticed better fuel mileage after break-in and more power when charging up a hill loaded when the engine temps rise. I believe the compression ignition starts earlier in the power stroke (lower case, not the Ford model HD truck) when the engine is good & hot giving a more complete burn and a longer cylinder explosion. So, I would expect a diesel to have better mileage in the summer. Another way to get this same combustion is to increase the cetane rating with an additive. But all my experiences described above are before adding any fuel additive. I have only burned a 1/4 tank of fuel on additive. And of course a summer fuel will give more miles per gallon. Last 2 winters in SC have been extra cold.