This morning I got up real early,everyone asleep and nothing to do, SO I decide to run my S40 dry and to prove what Arno has been saying all along, that the tank hols 16 gal. Since the "gas pump light" had been on the previous night, I knew it would not be long before the "fuel" message appeared! So I stopped at my local bagel shop, got a works bagel with chive cream cheese and a medium Green Mountain Hazelnut coffee (mmmmm)plus 1/2 gal of emergency gas and headed off into the Vermont countyside on my great adventure. Shortly thereafter the "fuel" message appeared and I reset my odmeter! I hopped on the Interstate(We basically have two) and drove at 55-60 mph for approx. 25-30 min and then did scenic back roads(lots of cows and horses) at 35-55 mph for 30 min plus. As I approached a familiar Mobil station with 64 miles on the odo and my trip computer reading 32.1 mpg......I chickened out and refueled! With the pump lever set on the 1st click(slowest flow rate), I put in 14.96 gal as it clicked off. I was then able to squeeze in another 7+ tenths for a total of 15.7 gals. This would mean that if Arno and Volvo are correct than the tank does indeed hold 16 gal!!!!!!!!!!!!!!!!!!!!!!! I have read that its a 15.8 "usuable" tank, and a 16 gal tank.....I actually think that if I had run it dry, I could of put in 16.2 + allowing for the filler pipe! So what have we learned???? 1st, I did a crazy but fun experiment, 2nd, that the Volvo gas guage is deliberatly set up incorrect.! If you fill up at 3/4, 1/2 or 1/4 tank, you always take 2+ gallons less than you think you would, (my opinion) thus Volvo is erroring on the side of caution!!!!! Any thoughts, Bill