piperca

I get 15 mixing it up with town/freeway with 4:10's. Best I've ever had is a smidge under 18, all freeway. Uncorrected with 265's ... I'm sure it wouldn't be much better corrected.

I'm really glad this thread hasn't attracted the "I get a constant 22 mpg" guys, that's when I shut off my computer!

bentwings

I keep track of my mpg very closely as well as cost per mile.
Winter fuel cuts the mpg by about 2-3 here and the ulsd seems to take another 1. This is when temps are below 10 degrees F. I get 15 to 17 at very low temps. When it gets to 20-30 deg, it picks up about 1. Over 30 deg I get 17-18. Summer I usually get right at 20.

Now about a month before I changed VP in Dec 06 mpg had dropped to no better than 14-15 on a good day. This was just as winter fuel comes full strength and ulsd started appearing at most pumps. After the change mpg was backup to about 17-18 in the very cold weather. The last fill was 18.7 mpg for 490 miles, so the VP has really helped.