[sm=smiley6.gif] Finally had the XC90 on the road (2006 2.5 FWD) and only got 16.2MPG. The on board info was saying 18.9-19.2 MPG. I really want to question the meter at the pump where I filled up on the highway. I also was averaging speeds of 75 MPH, maybe that is just too fast??? I even did an oil change before the trip. My expedition got 19 on the road.....

 

I wouldn't put too much faith in the onboard info; many manufacturers fudgethe numbers a bit in their favor.
Other factors would be
tire wear/size - any variation +/- can make a difference in speed and odometer,
distance traveled - more distance and fuelusedmakes for more accuracy,
the angle of the ground at the fuel pumps - differences can lead to varying levels of 'full'. You might have gotten a short fill the first time and a complete fill the next.

Also keep in mind that most gas this time of year is winter-blend, which will take a toll. I've seen a 10% drop from 2 months ago due to winter-blend. And different vehicles behave differently at high speeds. You will just have to find where the butter zone is on your XC.

 

Tire size: I may have larger than OEM tires, they were new when we purchased the vehicle. How can I find out what OEM size tire is for the 2005 with 17" rims? If there is a size difference can the onboard computer be reprogrammed to compensatelargertire size?

Distance: drove 325 miles, 97% hwy

Angle / short-fill:With as much asone gallon difference, I only gain one MPG for that tank.............

 

IIRC the tire info is located on the inside of the fuel door. I really don't know of a way to correct the computer for it. I don't know if the dealer has the ability or not, but you couldbring it up on your next visit.

The reason I brought up the possible other factors was because I went through a similar process setting up my ScanGaugeII mileage tool. It reads info straight from the OBD port so its similar to the onboard info, but it has room for adjustments to correct for speed and fuel used. One tip was to try filling up at the same pump each time (hard to do on the hwy, I know) to eliminate variations in filling. That way, you will only be left with the tire size factor. The ScanGaugeII was spot-on right out of the box for me (4.124 gallons pumped vs 4.1 gallons calculated).

But if you're looking for tips on better mileage in general, LoveMyS60 has a great post. Do a search; you'll find it.