n2oiroc, Youre absolutely right!!!!! Fuel and the fuels additive package has a LOT to do with dirty powervalves!!! What people don't understand is that todays gasolines are designed for 4 stroke AUTOMOTIVE engines,,,A WORLD of difference between 2 and 4 stroke CAR engines!!! The additive package(in todays gasoline) could actually be creating the problems with dirty powervalves... I've tried a few times to talk with the engineers at MOBIL and AMOCO (near Chicago) and they asked me a thousand questions as WHY I wanted to know their recipe (package),,, NEEDLESS TO SAY,, they won't release ANY information!!!! Its their trade secret!!!! Kinda like KENTUCKY FRIED CHICKEN!!!!! "summer gas" in chicago atomizes at +43 degrees F. and winter gas atomizes at -34 below.. if you used winter gas in the summertime,,, it would atomize in the fuel lines and create a "vapor lock" condition,,,,, SO,,, it is VERY important to the refineries to make fuel that adapts to the LOCATION and SEASON!!!!! If you consistently bought a tank of MOBIL super unleaded, and your car runs like DOGCRAP,,, and you bought a tank of SHELL super unleaded, and your car runs fine,,, NATURALLY you would buy the fuel that makes your car run better!!!!! PEOPLE get fuel from the LOCAL REFINERIES!!!!! That means that JOES GAS probably buys the SAME fuel that MOBIL sells at their stations.... Chicago has 2 refineries,, one is BP amoco in Whiting Indiana and the other is MOBIL in Joliet Illinois (both about 1/2 hour from Chicago)...... Fuel companies are NOT going to ship their product 8 hours on a TRUCK to get it to EAGLE RIVER WISCONSIN every other day!!!!! It just isn't feasible!!!!! Therefore, gas stations USUALLY buy their fuel from the LOCAL REFINERIES!!!! In CHICAGO, theres citgo, bp amaco,shell,gas city, marathon,texaco,mobil,thorntns, speedway,joes gas, teds gas franks gas, ernies gas,,,,,,, and the list goes ON AND ON!!!!! Do you know WHO all of them buy their fuel from??????????????? EITHER MOBIL OR BP!!!!!!! REMEMBER,, these fuels are designed for PASSENGER AUTOMOBILES!!!!! NOT FOR SNOWMOBILES!!!!!!! so boys and girls,,,, When i say that there is a LOT OF VARIABLES when it comes to dirty powervalves,,, PLEASE DON'T BELIEVE ITS THE OIL!!!!!!! Gary Oles nosboy