I hope I'm not jinksing it, but the last 4 or 5 fill-ups, I have been getting 19mpg's or better. Before I would get around 18 on a good tank with hwy driving, 16ish on a tank with a lot of city driving. I filled up yesterday and I got 20 mpg's. My best ever. I would say it's the warm weather, but I never got this good of gas mileage last year, and I haven't changed a thing. About a month ago I get high 16's, low 17's so I figured I would change my fuel filter (eventhough I only had about 10k on it) but never got around to it. Then all of a sudden, BAM, 19 or better. The last tank was about half city (and I was late everywhere I was going, so I wasn't driving easy) but still, 19.
Only thing I could think is that it is the 255/85 tires I put on before Christmas, coupled with the 80 degree weather we're getting.
Anyways, kinda random, but I've been jealous of all the guys saying they get 20mpg.

The tires did it. i never hit 20MPG untill i got my 285's. then when i got my 35's i got 22MPG once. but in the city my millage droped like a rock with the bigger tires.

I noticed a jump in mileage too recently. I assumed that the warmer weather has something to do with it. All highway I'm getting 19 or so at 75 mph, for about a month now - interesting that the better mileage started on a trip back to Atlanta from West Point, MS!

At times I see mileage above 20 if I don't run above 70mph and really baby it.

you did adjust for your tire size right? just curious because i kno that will adjust your mileage

last few fillups have seen an increase due to warmer temps and probably different cuts of blended diesel.

Most stations tend to go back to #2 diesel for summer. a few more btu's per gallon than #1.

My mileage took a jump last year and kept going up till it was getting 26+ hwy. Started smoking at an idle last fall, ended up changing injectors last month and now the mileage is back down to 18-20hwy. Check your balance rates.