MPG went to crap

[hilmar]

just rolled 3600 miles, mpg s been going downhill....wth?

started out 17 ish no problem on display and hand calculated.

now, display and hand calculations 12.8 13.5, using same station, premium....

and this is all prior to changing to 20 s w/ pirelli s ....

[v8_dave]

Is the circumference of the new tires identical? If that is bigger than the your actually going faster and farther than your computer thinks. Don't know what else it could be, maybe needs some more break in. 17 is pretty good hough IMO, it shouldn't go down during break in I would think.

[hilmar]

was happy with 17 to start, figured maybe even get close to 19 ish once broken in....

20 s and 18 s are from what i can see same diameter.

my 98 was a pretty consistant 18 19 mpg no problem..

i m wondering if the excess fuel smell in the oil has something to do with poor mpg.....

havent check that since oil change at 2300 miles.

[megaforcer]

I have never seen a Navigator that did 17mpg. Your computer was lying to you. 12 to 13 is normal millage for a Gator. You might see 17 on a good day on the highway.

[hilmar]

nope, 17 was the early norm, hand calculated.

all i do is highway driving, 2 miles on and off parkway.

my 98 was even better yet, breaking 20 mpg, hand calculated.