I have a 96 audi A4 quattro and was wondering what would happen if I started using 87 octane fuel in it. I have been putting 93 octane fuel since I bought it. Gas here in SC has now hit 3.07$ for premium and I was just wondering If 87 Would hurt the car at all? What is the lowest Octane rating I could get away with putting in my audi Without causing It any damage?

 

In a 2.8, you can get away with regular gas just fine.

 

you will lag on performance and youre mpg will drop so it wont make a diffrence because it will equall out if not you end up paying more in the long run

 

$50 every two weeks for me93 octane.

 

The difference in a tank of gas between regular and premium is what? Maybe $5?? Your car will run ok on regular, but your knock sensors will be working over time, andyou will lose performance/mpg as said.

 

What's the compression ratio of a 12V motor? I rather doubt it's high enough to necessitate high octane fuel, unless you've got some manner of forced induction.

 

The 12v engine has a high-ish compression ratio, I think 10:3 : 1. Which is why super charging or forced inductionis difficult.

 

I guess everyone agrees that premium is the way to go because the loss in performance and fuel economy will neutralize the cheaper purchase price...but here's another bit worth considering. I always fill up at the Safeway because it's where I do my shopping so I generally get a $0.17 discount, so it's much cheaper than anywhere else. A few nights ago, I was desperate for gas so I filled up at Chevron because it was the only thing around. I think I ended up spending $5 or $6 more for the whole tank, but I have been getting more than 4 mpg better on this tank driving the exact same route I always do during the week.

Anyway, what it comes down to is that you won't save money buying regular and you may even be better off buying the more expensive premiums.

 

In my bikes (which lack knock sensors), I'm always told to run the lowest grade possible without pinging. Octane actually makes the fuel less volatile to prevent compression ignition before the spark. My last Ducati had a compression ratio of 10.3:1, and it loved regular gas.

*edit* My Aprilia has a compression ratio of 11.4:1, and I won't put anything less than 93 through it. I'm afraid to try mid grade. 10.3:1 on a 2V per cylinder motor will handle regular gas just fine. The turbo guys need it, but the V6 crowd really don't.

 

The heads on your bike shouldcool faster/better than any car engine. They might have the same compression ratio, but you have to take heat into account when debating pre ignition/knock/pinging w/different octane fuels.