Exactly as davidj said and I said it's the "last 600 miles".

 

I drove to Fla. and on the first tank I put 723 mi. on. When I stoped to fuel up I put in 33.94 gals for a hand calc. avg of 21.3 mpg. That ws going south on I75. The o/h read 23.3 so its off by 2mpg. Still happy with the actual.

Jim

 

mine was off 4 miles per gallon on a 170 mile trip, I'm getting 17.2 on paper truck just rolled 10k. Hope it will get better