Gas Octane

[zoomzoom]

Anybody got an opinion over octane levels for 545i, or the X5 4.8. I am of course using high test, but with the high price of gas, what about using regular? ZZ

PS, if previously discussed, please excuse the repeated question.

[Hoppy's535i]

should be in your owners manual, probibly say 91

[Jrf786]

91 octane should be the minimum. If you use anythign less, you will get decreased gas mileage, and less performance. Now who wants that?

[billB]

High vs. Low Octane. How much do we know?

A. If we run our cars on low octane, we will end up with a ping/s aka detonation.
B. But we also know knock sensors do work hard at compensating for some via ignition timing.
C. High octane is NOT cleaner than low octane.
D. High octane has LESS energy than low octane! No? but has better detergents.
E. High compression engines demand high octane.

Open questions:
A. Due to high oil prices, can zoom zoom find the lowest possible octane at which his engine does NOT knock with? (Forget about what his manual says for now; think OPEC, knock sensors; high/low compression ratios/chips etc) if yes then
B. Can zoom zoom get better results with higher octane? In terms of Performance?
C. Remember no knocks here since these sensors are taking care of his ignition timing and he is running with relatively high compression engine…advance etc? Any thought?

regards
billb

[The Deuce]

The higher the Octane the more it resists combustion. There shouldn't be any more detergent in 93 than 87.

Higher octane lets you run more timing, which will net more performance.

[BMT]

This is the kind of question that can often get as many different responses as people you ask. However, despite your car having a knock sensor there probably detonation occuring at lower-levels that you are unaware of. I have heard many cars with knock sensors pinging. If I run anything less than 91 in my 540i, which is the highest octane you can get in California you will hear significanting pinging. Regardless, a 545i is a 60k thousand car and an X5 4.8 even more. Buying cheaper gas will save you a little bit of money over the long haul, but it probably isn't worth it when you consider the cost of your cars and the potential long-term wear.

I having a racing car and after my last trip to the track I had 5 gallons of left over 100 octane (5.95 a gallon). I decided to put it in my BMW when the tank was near empty. I feel a pretty massive difference...much fatter torque curve.