Hi I am looking to purchase a diesel truck but don't know
which of the three is better on mpg just stock for now
duramax, powerstroke, or cummins. I won't be towing any
trailers or carrying any loads, just driving to and from work
which is only 3 miles away in town but would be taking the
family out every now and then. Any advice will help with the
You have an interesting question. The Diesel engine gets it's fuel economy mostly from the fuel. Diesel fuel has more heat energy than gasoline. Turbocharging will help increase the power and fuel economy. Any of these three choices will produce economy. Not towing a trailer, go with a lower number rear axle gear ratio ie, pick a 3.08 not a 4.56. Next issue: you aren't driving far enough to heat up the oil in the engine. Diesels thrive on heat, you should get the engine hot enough to burn of the moisture in the oil. 3 miles per trip equals an unhappy motor. Even gas engines won't be happy at 3 miles per trip.
If you are going to be commuting a short distance and not pulling a trailer or hauling a load DO NOT BUY a diesel. Short trips soot up some of the sensors and this will cause it to be in the shop more than it is out. A friend of mine had regular issues with his Dodge until he stopped driving it a short distance to work every day (2.5miles each way).