Definiive answer ?? Y or N "05 T6

My understanding: it will "run" but not make full power.

With lower octane gas, to prevent detonation, aka pinging, the car's brain adjusts the timing away from the point which would yield maximum power.

You can run regular fuel, but the ECU will retard the timing and reduce boost pressure somewhat and you will get less power. You'll also get slightly lower fuel economy, whether this will be noticeable or not you'll have to find out.

He said his car is a T6, that's the top of the line high pressure turbocharged engine and will most definitely benefit from high octane fuel. If you don't want the extra power, you may as well save thousands and buy the light pressure turbo or naturally aspirated models. Some of us like the extra power and don't mind paying a couple dollars more to fill the tank.

Run on minimum rated octane stated to save on gas costs. Only high compression engines need high octane, its stated on what to use in you manual, High will give more power and a bit better mpg but nowhere near enough to make up cost difference, you might get 1-2/10th better mpg. If you have a full car and are going through mountains with the AC on then the extra power may be worth it. High test only cars are for rich suckers who dont care about money.

-------------------------------------------- My 1.9T S40 calls for premium - I ran some tests on different grades of gas and, while drivability didn't suffer, there was a decrease in MPG. Once the MPG was figured into the overall cost the difference between premium and mid-grade was less than a nickel per gallon.

I beg to differ from Joerg's opinion but I believe there can be a big difference in gasoline. It's true that there are minimum standards that gasoline must meet, but they are just that, "minimum". I think the better brands exceed those specs, particularly in cleaning additives. The composition of gasoline is very complicated. It can contain as many as 50 different chemicals, probably not all at the same time, but still, a particular octane gasoline may be very different between different brands.

I do agree that using a higher octane fuel than needed will not improve performance. However, remember the R+M/2 formula. Different brands can reach the pump octane number with different R and M numbers. That can make a difference sometimes, particularly with high combustion pressures, ie: turbocharged engines, among others.

Steve E

"Detonation will cause piston and ring damage, top ring groove wear, scoring, sticking rings, loose head gaskets and possible complete engine failure."

see:

I'd heard that it all comes from pretty much the same place. The only gas I've ever had problems with came from Arco, and that was on more than one occasion. I chalked it up to stale fuel or water contamination but I'll never know for sure. I figure the gas may be the same, but the storage conditions may vary.

My dad put cheap gas in his 240 Turbo a few times and it would ping like crazy. I think the boost was at around 12 psi and of course there's no knock sensor on those cars. The power limit with virtually any turbo motor is determined by the onset of detonation, modern engine management will retard the ignition timing and/or back off the boost pressure to prevent it, but why spend the money on the fancy hardware then not let it work to its full potential?