Duramax Fuel Economy

Hello Craig,

Look up your owner's manual for the following spec: max torque at xxxx rpm. You should get the best fuel economy at xxxx rpm in top gear/overdrive. Good luck.

Franko

Hello dperez,

If you have a stick shift, keeping the rpm at/near that reading in any gear will give you the optimum mileage for that gear (e.g., going up a very steep hill in 2nd at 1800 rpm, or a steep hill in 3rd at 1800 rpm, etc.). For automatics, if your tranny is gear-hunting, manually select the lower of two gears it cannot make its mind up on and keep it at/near that reading.

BTW, that's pretty good city/highway mileage. We get 22 mpg highway on our '98 6.5TD 4x4 Tahoe. 26 mpg highway on our '86 6.2NA 4x2 Sub. But they've got much less torque/hp than your D-max. Aaahhh, I can always dream...

So my 2004 GMC 1500 CC with the 5.3L will get the best mileage at 4000 rpm's since it makes its 335 ft-lb of torque at that rpm? I find that awfully high and probable an illegal speed to be traveling.

they're talking about the Duromax,not your 5.3.

******************** There are three kinds of lies; lies,damned lies,and statistics.---Disraeli

Just curious, what are your truck's specs for:

1. Max Torque at xxxx rpm
2. Max HP at yyyy rpm

Horsepower: 295 hp Max Horsepower: 5200 rpm Torque: 330 ft-lbs. Max Torque: 4000 rpm

Just for "Max" comparisons:

2004 5.3L Gas V8, HP 295 at 5200 rpm, Torque 330 at 4000 rpm 1998 5.7L Gas V8, HP 255 at 4600 rpm, Torque 330 at 2800 rpm 1998 6.5L TD V8, HP 180 at 3400 rpm, Torque 360 at 1800 rpm 2001 6.6L TD V8, HP 300 at 3100 rpm, Torque 520 at 1800 rpm

Of course, the gearing/final drive ratio/tire sizes will determine the speed at the above RPMs (on the average between 55-65 mph). Nevertheless, the max torque figures at the specified RPMs will provide the most efficient mileage for the engines mentioned above.

gear/overdrive.

Maybe the engine is the most efficient at max torque, but I don't think that I will get the best mileage since I will be traveling far north of the speed limit.

Far north of the speed limit, I would have to agree as the engine would be expending much of the energy generated just pushing aside air. Again, gearing/drive ration/tire size all matter.