Just completed a 2800-mile round trip from my home in BC to the Santa Barbara area of California. Most of the driving was on Interstate highways or good 2-lane roads where speeds were close to what you do on the Interstates. The odometer now shows 248,700km (154,500mi).

Overall trip average was 27.0 MPG(US), leaving out the 150 or so miles of urban driving at my destination. So strictly highway.

In other posts here, I have claimed highway economy of 30 MPG, and that was the case, but it involved slower speeds in the 55-65 MPH range. This was my first extended test in this car with higher speeds of 70-75 MPH. The brick-like shape of the S90 is a very good use of space, but not aerodynamically efficient.

Many people on here have spoken of 26-27MPG and now I see my car is right in line with that. For a while there, I thought maybe I had an unusually sharp-running one.

I saw significantly higher and lower MPG readings on individual fillups, which did not reflect actual fuel usage, but were due to inconsistent filling technique, or the car sitting on a tilted surface, etc. I always get fantastic gas mileage on my first fillup in Oregon. Self-serve is illegal there, and the pump jockeys never top off the tank like I do. So the mileage looks great until the next self-serve fillup (in Calif. for example) at which time it looks terrible. It's important to get an average, and not to rely on one single data point as being meaningful - it's probably not.

The return leg of the trip covered 1320 miles in two days. The S90 is a nice highway cruiser: quiet, adequate power, good cruise control, reasonably efficient and comfortable seats. Guess I'll keep it a while longer.
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Bob: son's XC70, dtr's '94-940, my 81GL, 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.