Gas vs. Diesel

RV Clinic - Diesel/Gas image

Q: I am curious about the gas/diesel truck debate. Considering fuel mileage, does the diesel truck get better mileage than the gas truck? Is the cost per mile about equal between a gas and diesel? I can never get a diesel owner to tell me the true mileage they get, they always say, “Well….”
Mike Cressy, Via email

A: Fuel economy can be 20 or 30 percent higher with diesels, with some reporting closer to 40 percent under ideal driving circumstances. Today’s gas engines are becoming so efficient that the gas-to-diesel MPG gap is narrowing. So you can compare the prices of gas and diesel in the areas you intend to operate in with that in mind.

It’s very difficult to make direct comparisons between the two types of engines because there are many variables. The trucks have a very different feel under load and different performance. Diesel trucks also have a considerably higher initial cost, and service — when needed — usually costs more, but diesels generally last longer and have higher resale value. Take a look at the truck’s service requirements, how many quarts of costlier diesel-spec oil each oil change requires, the cost of the oil filter and fuel filters, and so on, and run those numbers out to 100,000 miles or so. Compare the costs to those from a gasoline-powered truck. That’s one factor in figuring if the diesel is right for you. Therefore, how long you keep a vehicle also makes a big difference with regard to how soon the increased fuel economy will start paying back the higher-cost diesel-engine option and other related costs, including frequently more-expensive fuel. Diesels also often have a higher tow rating than gas models, so if you tow heavy trailers, a diesel may be a better choice. — K.F.

Two men - Ken Freund and Jeff Johnston - standing near truck To send your questions to RV Clinic, write to 2575 Vista Del Mar, Ventura, Calif., 93001; or email [email protected]. Also, check out TrailerLife.TV for our expert RV how-to videos.


  1. I installed the tank monitor on my 2007 sierra 5th wheel but when i did the job i would do all of them. The only thing is i had to install one more wire to each unit because of the 3rd wire. With a long stick i pushed the 3rd wire in the underbelly to go with existing wiring back to the new control unit. It’s the best , no guess work on all of the tanks and also gives the battery condition of the rig. A second person is good to have also. I also took pictures of the original wiring at the control unit and marked the wires to get it hooked up right.
    I would do it all again it’s the best. Roger Hime Summerfield Florida


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