The Grand Marquis is my daily driver, and runs on Euro II rated gasoline with a sulfur content of 500 ppm. The quality may have been fine back in 1995, but is quite dated right now. To be fair you get what you pay for, and at 91¢/US gallon it's a fair price I suppose. Having said that, Euro IV rated gasoline with an octane rating of 95 RON (91 AKI) and a sulfur content of 25 ppm is available for the handsome sum of $3.93/US Gallon. This is also dated, however, as they are now using Euro V in Europe. Now if the Euro IV stuff will keep my combustion chambers cleaner, provide better gas mileage (I average 17 MPG with the dated stuff) and help extend the life of my engine, I don't mind paying 4 times more. But will there really be an advantage of switching to low sulfur gas with higher detergency? I suppose it would help extend oil changes, but that's the only advantage I can think of. Thanks!