Please post how changing timing affected your fuel economy and power levels here.

I would be interested in learning how different timing settings affect fuel economy at different speeds. If you found that changing timing gave you more or less power did it make driving at your normal speeds better or worse?

With luck information provided below by many who have changed timing or even kept stock timing could end the "what should I set my timing at" threads.


Below is my example showing what timing, gears, transmission, and tire size I have and what mpg I can get in what kind of driving. If others would also post their results it could help to show what combination of gears, tires, and timing works well for the conditions different people drive in.

I have an 1996 stock engine with an automatic and 3.54 gears. My tires are 235/85/16 with an uncorrected speedometer so it reads about 4.5% low. My timing should be set at 14 degrees. That is what the tag on the timing cover tells me. The injection pump has been replaced and has a cummins rebuilt sticker on it. That means it might have a different timing setting than is called for on the tag.

I got 23.5 and 26 mpg at 54 mph and 1,500 rpm. I also got about 18 mpg at 70 mph. All of the above was pure interstate driving. Mixed driving with city and driving at 50 to get to the city gave me about 18 mpg.