Do octane levels in gas actually effect car performance?

About ten years ago I saw a blurb on the evening news that some independant study group had done a study which revealed that higher level octane gases actually harmed cars’ engines rather in increasing performance. I’ve never heard anything since about it. I wonder if this has been discredited since or been looked over conveniently by the media so that their advertisers could sell more expensive gas. Does anyone know for sure? Personally, I’ve been using the lowest octane gas ever since.

Try http://www.straightdope.com/ubb/Forum3/HTML/005392.html for a recent discussion. The short answer is, it depends on your vehicle. Check the owner’s manual.


“If you’re so pro-life, do me a favor: don’t block medical clinics, lock arms and block cemeteries.” – Bill Hicks

Advice:

search engine

This should be in GQ

Sorry for posting a previously (several it seems) asked question.
Will be more careful next time.
Thanks however for the link!

I’m moving this to General Questions.

Please don’t do this again, read the damn forum headings before you post, okay?

your humble TubaDiva
Administrator
The Straight Dope

I found some related info about performance boost with raised octane. Some supercharged engines can literally destroy themselves if left at maximum throttle for an extended period of time. The problem can sometimes be solved with water or alcohol injection systems that would cool the combustion chambers long enough for maximum takeoff power in an airplane for a brief period.

During WWII US had 150 octane aviation gasoline for planes without water injection equipment. That allowed P-51 Mustangs to run at 67 inches of manifold pressure for up to eight minutes in combat. The higher octane did not in itself provide more power but allowed the engine to be force fed more than was possible with lower octane fuel.

In my area, the difference in price for mid grade, doesn’t make sense.
87 octane = $1.29
+2pts to
89 = 1.47
+4 pts to
93 octane = 1.52/gal.

Also, if you are thinking about fuel additives, save your money, octane boosters that come in the pint or quart bottles do not work.

It is however possible to increase octane with the addition of toulene or xylene, one part to 2 parts 92 octane = 100 unleaded.
-good for those that feel the need to pressurize their manifolds :wink:

104+ used worked for me, when I had vehicles with higher-compression engines (10.1-1), and higher-octane leaded was no longer available. Perhaps because it had xylene in it.

A local friend used to put xylene in his Turbo TA to keep it from pinging, but he first added aliphatic naphtha to the xylene. I don’t remember if this was to stabilize the xylene, or because pure xylene would prematurely rot the rubber gas lines. Maybe both. Perhaps a chemistry expert could address this.


“If you’re so pro-life, do me a favor: don’t block medical clinics, lock arms and block cemeteries.” – Bill Hicks