Myth's about Premium Gasoline

[Bill87GN]

don_davi, keep using 87 octane if it's working for you. Pinging/knock sort of sounds like marbles in an empty coffee can. That's the best way i can describe it. If you hear an audible knock, then that's a lot and for some of us with boosted applications, such as the Lightenings here and the N2O'd Civic, that usually means it's too late

Nice article by the way, but it doesn't take into account boosted apps like mine or other turbo'd/s'chrged/nitroused cars. I run the highest octane I can on the street. Here in Boston usually means a homebrew of 94+xylene mix, which usually equates to about 100 octane. At the track it's strictly C16 (116 octane) for those 27psi runs :

happy motoring folks

[FalconGuy]

You really wouldnt hear a knock on a modern car, the knock sensor would just retard the timing to prevent the knock. Result= Less power but the engine will not be damaged.

To see if you have a knock sensor TAP the block with a hammer while its running, listen for the reaction of the engine. No reaction= no sensor

[Ben Z.]

Bill87GN, sweet car! Man, you are running over 25% xylene on the street? Gets pretty expensive, huh? Here's some more good info for you guys. Check out the Fuel section on this website:

http://members.rennlist.org/951_racerx/TOC.html

[Bill87GN]

Ben Z,
Yeah gets pretty expensive, but I still knock down 20+mpg and I don't drive it too much. It only sees 8 months of the year anyway. I guess I am lucky there is no real high octane here or I'd be broke, lol. NH has a bunch of stations, but too far to drive for just gas. Might as well make it myself.

Great site you posted!! that should keep me busy the rest of the day at work, lol

[Jesstzn]

Newer VWbs all call for 92 octane and running less shows a remarkable loss of performance and gas milage actually drops off. Mine is a 10.2/1 30 valve V6

[endus]

Argh...the octane discussion...OH NO!!! I can't read this entire thread because I have done my research and I will end up responding to hald the posts with all the misinfo that's out there...so let me just throw my 2 cents in.

People are correct in saying that running a higher octane fuel than is RECOMMENDED BY YOUR OWNERS MANUAL is unnecessary and wastes money. However, you should run whatever the owners manual says. The reason for this is that the ECU, in order to prevent knock, will retard the timing slightly. This will have the side effect of reducing both fuel economy and power. The estimates used by factory engineers are usually conservative, so running a higher octane fuel than is recommended "just to be safe" is unecessary. I have also heard that you may experience some knock running lower octane fuels as the engine attempts to advance the timing as far as it can. Don't know if this is true but knock is very bad for your engine even in small doses. If you care about your car and want it to run as efficiently as it can, making the most possible power and getting the best possible economy you MUST run the octane level that is recommended by your owners manual. The difference people see in fuel economy and feel in the ***-dyno when running premium fuel versus regular (in a car that requires it) are REAL.

Now that I've said that, take a look at this...

http://www.motorvate.ca/mvp.php/506

Given that the one plug has more miles on it and there is an appreciable difference in the appearance of the plug, I would say that the differences from standard gas that he cites are significant. Now I've heard about how the truck pulls up to the shell station then goes across the street to Mobil, but there is enough anecdotal evidence to justify the trivial cost difference to me.

What do I run? I ONLY use Sunoco Ultra 94. Yes, I may be wasting my money, but the price difference is not that significant and if there is even a chance that the above link proves anything I will stick with it. Then again, I plan to own this car forever...if I didn't care I might not spend the extra money. To me the difference in cost is not significant enough. Yes, I am doing exactly what I said not to and running it "just to be safe" but I'm fine with that.

[endus]

One more thing after reading some more of the thread (I know, I said I wouldn't). That GAS FAQ that was posted is very good and was where I learned a lot.

Also, people saying that modern engines are tuned to not need high octane and that using low octane fuels are fine do not know what they are talking about. Low octane fuels are only fine IF YOUR OWNERS MANUAL SAYS SO. In today's world we have car manufacturers wringing a lot of power out of relatively small engines, using FI, etc. The differences in the power and economy you get with a lot of these cars is absolutely GIGANTIC...you should be running what they recommend and no less!! I understand why octane has become this thing that everyone says is a myth, but people ahve taken shooting the myth down WAY too far. Octane has a function and they sell different grades of gas for a legitimate reason. People have taken the mythbusting way too far and now everyone thinks it's fine to run **** gas ni a car that rewuires 91. The gas stations will lie to you but the car manufacturer will not...listen to them.

What people say about FI and tuning and enhanced ECU's is all true too. A lot of those ECU upgrades basically just advance the timing even farther...therefore requiring an even higher grade of octane. Again, just run what they tell you to run and you'll be fine. By the same token, though, people running race fuel...100 octane + and telling you that their car is hella fast because of it are full of it. As DavidB said, octane just prevents detonation...it does not make any more power by itself. It does allow you to make other changes to the engine which will make more power, but a stock ECU isn't going to say, "hey he put race gas in me, I'll advance the timing even farther!". It has a preset limit to how far it will go.

A lot of places in high altitudes also don't offer as high of an octane rating because I guess in higher altitudes detonation doesn't occur as often because of the lower air pressure. That's why you don't see Ultra 94 or even 93 out in Colorado, etc. like you do at places which are at sea level...or so I'm told at least.

Again...just run what they tell you to run!!