OK did the tank/gage test this afternoon. The 450i book claims it has an 8+gallon tank. Siphoned out the last almost a gallon as best I could so I believe the tank was as empty as I could make it. As Crossbolt stated there are 5 bars on the fuel gage and when I was done siphoning no bars were showing and the little gas pump symbol was flashing. So I added 2 gallons of fuel and now the gage shows 2 bars, then added 2 more gallons and gage showed 3 bars, added 2 more gallons and all 5 bars were shown. Proceeded to add the last two gallons and it took all but mabey 6-8 oz at best. The manual states to not fill the neck of the tank so I quite pouring when it sounded like it was coming up the neck. So.....after it uses the first 2 gallons the gage should start to drop, at 2 bars I should have a little over 2 gallons of gas left in tank, at one bar I think it would be safe to say its time to add more fuel, I understand you do not want to run a fuel injection system dry. Hope this helps someone.....