The last two tanks of diesel have calculated out to less than 15 mpg. I typically get 19 mpg, would cold temps or winterized diesel have this effect on my mpg? Three tanks ago I started using Stanadyne Performance Formula fuel additive and noticed a difference in power and appeared to go forever before fueling up again (did not run calculation). Could I have a problem other than the possibility of bad fuel? I have about 4500 miles since my last oil change and the same on my fuel filter. The stock filter minder is in the safe area. It shoud be noted that I get my fuel at the same place everytime I fuel up unless Im on a long road trip.

 

Winter fuel will drop you a couple miles per gallon. I also just started using that additive and I notice an improvement also.

 

Warm up times, if long, will lower MPGs, I got about 13MPG last tank. Typically get around 17-18.
Mike

 

Not sure where you live, but with all the cold weather that will zap your mpg's.