A4 Octane
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As I understand it
The engine has a knock (ping) sensor. When knocking occurs, the timing is retarded which decreases performance. So, lower grade gas "shouldn't" harm the engine. <p>I've owned a couple of cars that got hard to start after a diet of 87 octane.
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Gas is cheap....not in California...
I just paid $1.43/gallon at Chevron...last two fill ups...and I don't live in a place<br>where they normally have abnormally high gas rates...like right off the freeway in <br>some rural place.<p>I only use 92 octane...and I recommend you do too.<p>Just a dose of my 2 cents worth.<p>Steve S.<br>97 2.8QM
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Don't recommend it.
The 2.8 30V is pretty sensitive to octane, in my experience. With anything less than 92, you can really feel the power surging as the computer retards and advances the timing. With 87, I've even experienced momentary knocking, and the surging is horrible.<p>Charles<p>PS: I'm not the one who put the 87 in, but it didn't take me long to notice! I couldn't wait to get to the gas station to fill up with premium. :-)
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High Octane Antics
Higher octane gas does only one thing, increase the threshold for knock (detonation) resistance. It doesn't do anything magical and [as I understand it] actually has slightly less energy per gallon. It won't give you any more mpg. The A4 has a high enough compression ratio that it requires premium gas. 89 octane would probably suffice on flat roads and no WOT. On a hot day, up a long mountain, the engines knock sensors may signal the ECU to retard the ignition timing enough to overheat the engine. Severely retarded ignition timing actually causing a viscous loop (retards timing, it reduces power, you press the accelerator down farther etc., etc.) So you should use the octane gas listed in your owner's manual and around town can probably get by with one grade lower. You bought a 30k car, get the right octane, brand name gas.