Type of Fuel
 

Hello everyone, I just bought a 2007 A4 3.2, I want to use regular fuel in it, Has anyone had any experiences doing this ?

Re: Type of Fuel
 

I have never used regular fuel, even in cars that were much cheaper than the Audi. I have found that I get better mileage with premium gas under identical conditions (or as much as I can make them identical) and the cost isn't really THAT much of a difference.

I subscribe to the school of thought that you bought a premium car, you may as well treat it that way....why do you want to use regular gas?

Unless you're driving crazy amounts each year the savings are negligible in the long run in terms of other things we waste money on.

Re: Type of Fuel
 

Yes that is part of why, I put 45 to 50,000 Kms on a year so the difference adds up fast.

Re: Type of Fuel
 

technically your O2 sensor will adjust to the gas and pull back timing... so if you must, you probably should be able to get away with using 87...

Re: Type of Fuel
 

Thank you, But if I want to do a day of play not travel , will it adjust back to premium ?

Re: Type of Fuel
 

yes, it adjusts back as the O2 sensor relays data... if you're pre-planning a fun day, I would let the tank run as low as possible and fill up with 94 sunoco...

Re: Type of Fuel
 

Thank you very much.

Re: Type of Fuel
 

Great observation, however this is technically impossible. The higher the octane fuel the less BTU it contains, you will actually get lower gas mileage with a higher octane fuel because the BTU value is lower then regular gasoline.

The knock sensor will pull timing depending on knock. A lower octane fuel while it gives you better gas mileage will not have the AKI of a higher octane fuel (AKI = Anti Knock Index) so you will not make as much HP. This only matters at 100% throttle near the engine peak power output which on the V6 and 1.8T is high 5k-low 6k rpm area. If your just daily driving the car, regular fuel will be a better choice and will not cause any long term issues.

Generally most high octane fuel uses ethanol which has half the density of regular fuel so you must burn twice as much of it for the same power. Adding this to regular fuel increases the Octane Number but goes to further reduce the BTU value of the gas. So you will get even less mileage on Sunoco Ultra 94 than even just 91 without ethanol. If you have a huge turbo and make massive power then yes that a good choice. In a stock car, there is just no point.

As a matter of fact higher octane fuel will produce less power then using the fuel rating that the car is designed for. I'm not sure if it would show up on a dyno with 94 vs. 91 but if you put in unledded Pro Fuel MK4 114octane (Kinda Like VP C16 but no led) into a 1.8T you would probably lose 10hp because the car doesn't have enough HP or spark power to burn it properly. The higher the octane, the harder it is to ignite which is great for a 500hp car (my talon which runs 11.7 @ 119mph loves it) but the 1.8T or Boxster, not so much.

Regards,

Re: Type of Fuel
 

Good answer , Thank you very much. I understand. I have a Suzuki Hayabusa and have been running regular fuel in it since new,In fact Suzuki recommended it.

Re: Type of Fuel
 

I always ran regular in my CBR600 same as you. Better mileage when cruising and still worked at 16,000rpm with 12:1 compression no problem. My bike did 11.2 @ 126mph in the quarter on regular gas, so it was obviously not affecting the performance at all.

There are a lot of misconceptions regarding fuel and octane out there. People automatically assume higher is better but not always and not on every car. Hell I ran regular in my talon when I was just driving somewhere long distance. I drove to E-Town from home here 8 hours away and ran regular the whole way. I drained the tank at the track (had a switch valve so I could easily) and filled up with race gas from a can ran all day, drained the race gas left back into my can, and re-filled up my regular and drove home. The car even with 424whp would get 30+mph on regular gas on the highway. I could run 12psi of boost even from my 60-1 and make about 250hp on regular gas with no detonation. The car would go 13.2 @ 105mph on 12psi with regular gas lol...