Has anyone else compared real world fuel economy (miles traveled vs. gallons filled) to the fuel economy given by the navigation system. I tried searching for any threads, but I didn't see one.

I consistently get 1-2 MPG lower than what the computer states. I have stock 18" rims with standard-sized tires. I did add a K&N filter approximately 5k miles ago, but made sure to leave my battery disconnected all night before re-connecting. I've even tried overinflating my tires to 40 PSI.

I figured it would give me a closer value (within 0.5 MPG) over a 300+ mile period. My drive is about 90% highway and I get somewhere in the 24-26MPG range, although the computer claims 25-28 MPG. Am I missing something, or is this common?

I guess I should give it a little more credit, since my outside temp gauge is usually 5-10 degrees off.

With premium hitting $4/gallon in California, I figured it is time for full blown G35 hypermiling!

 

I always say that the navi mpg are inflated. Gotta do it the old fashioned way

 

I've never had a car whose computer calculation on mileage was correct. Nissan's especially. Normally 2-3mpg off on all my Nissan's.

 

what the computer reads will always be off... either more or less