Diesel mileage


I recently replaced my 94 f250 7.2L diesel truck with a 04 Ram 2500 5.9L diesel truck. The mileage is about 1/3 worse in the 04 than in the 94. Since the engine is smaller in the newer truck, this doesn’t make sense to me. Is it a brand difference or a sign that something needs to be checked in the engine? It runs smoothly so I’m not too sure about that. Any suggestions?


Need more details. What are the mileage numbers? There are lots of factors, such as drive ratio, driving habits, loads, etc.


In the ‘etc’ you can consider the 10 tear newer truck with all the added pollution components.


As far as I can tell, it is under similar driving habits. I don’t know what the ratio is - too hard to check now as it is sleeting outside. The “new” truck has about 30 K and the old truck about 120 K.
I hadn’t considered the diffence in the pollution controls.


Um, by “mileage numbers”, I think he meant fuel economy figures.


I doubt if that is the case, but a smaller engine may result in reduced mileage if it is too small.

My guess is there is a problem with that engine and that may be why it was on the market. There are many things that can cause a diesel to have reduced mileage. Timing is a big one. Another very possible problem would be the final gear ratio. Someone may have ordered a lower final ratio to get the same towing ability.


I don’t think there has been much done in the last 10 year’s diesels in the pollution area. That is happing now, but in general it is not resulting in lower mileage.


Injection timing, oil viscosity, final gear ratio, wind resistance, internal engine friction, tire rolling resistance, winter vs summer fuel, box cover or not, manual or auto trans, driving habits, road conditions and terrain are a few things that can effect fuel mileage. Also, your mileage checks must be done over a few tanks; not just one.