Dozman

What amount of racing fuel (106 Octane) is ok to use in a shark? I have recently found a gas station that sells 106 octane near me. I am curious as how much is adviseable to put in with say 94 octane? Or is it ok to run straight 106 octane?

John D.

Curt

I have run either 106 or 108 racing fuel. Its the stuff we run in our dwarf cars that are powered by 1200cc motorcylce engines. I had probably a couple gallons left in the tank before putting in about 6 gallons of racing fuel. Seemed to run pretty darn good. But at 4.50 or 5 bucks a gallon it gets pretty darn expensive. My car is a 79 with no computers and not too many sensors or anything so I wasnt too afraid of hurting anything.

How much per gallon does that station charge. Also, getting it from the station sometimes they over estimate the true octane rating.

Normy

Doz-

Before I put my catalytic converter on, I tried running my '85 S2 on 100LL avgas. It felt slightly down on power, and after a few days even began running a little rough. It was obvious that this was too much octane for my 10.4/1 compression. I think 100LL converts to 104 octane for road use.

Normy
'85 S2 5 Speed

Tony

WHY?

Higher octane fuel doesnt mean more power if you go to the gas station, put it in your tank all other things remaining the same. Your wallet gets lighter, thats about it.

Odds are you may even loose power going to 106.

Correct me if im wrong folks, but thats the way i have understood it. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

BC

I have found that SLIGHT increases in octane from the California 91 octane gas DOES help. But you, Doz, have 94 octane available to you, and it, I am pretty sure, is more than enough for the S4 engine.
We, were the fruits and nuts grow, are subject to 91 octane iffyness, IF THAT.

I have added toulene with very good results.

Although, as Mike Schmidt, my good 928 acquaintance from Chicago has said, you have to be very smart about what you add, because you may actually LOSE power.

Big Dave

What about 89 octane vs 93? Should I be able to notice a difference? Probably not. I've assumed the 93 is better for the car and so I always use the 93.....$1.6x per gallon.

Doz: how much are they asking? There's a few places here in Royal Oak that, I believe, sells the 104 for $3.65 a gallon <img src="graemlins/oops.gif" border="0" alt="[oops]" />

I suppose they're catering to the Woodward Cruising crowd.

chris928

There's no "may" about it. Higher octane = lower power. I'm amazed that more people don't know this. You should only use enough octane to eliminate detonation and NO MORE. Anything beyond that and you WILL lose power. Instead you should be looking into using tolune as an additive, a couple of gallons per tank or so. Toluene has very high octane, but more importantly, it also has more SPECIFIC ENERGY, or energy per gallon. Octane has little or none.

Please use the correct octane and send me the money leftover!!!!!!

Bill 86.5 928s

I'm also curious about octane..My father-in-law told me that a high octane fuel burnes slower and not as hot as lower fuels... is this true? does it help in engine op temp? I always wondered if it was true..Bill 84 928s

Mike Velez

The higher the Octane the more compression it can handle before it spontanously combusts. Therefor high compression engines need high octane fuel. Race cars that use super high octane fuel need that fuel to run correctly. Higher octane fuel does burn cleaner than lower octane fuel.

John Struthers

Punch up "gasoline octane ratings" on your browser.
Everything you wanted to know about octane....gas etc <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Drewster67

My 84 Euro requires 98 Ron,I haven't found a place that sells anything over 91 except for a station 25 miles away which sells Trick Racing Gas @ 107 Octane.

I found in my own trials that at 91, my car will not detonate, but if I add a octane boost gas additive (which will bump up the octane from 7-10 points) - My shark runs cleaner and quicker.

Rather than going with gas at 106 (which I feel may be too much) try using a octane boost additive. You may like the Results at the fraction of the cost.

D67 <img border="0" alt="[king]" title="" src="graemlins/r.gif" />

jpitman

RON means 'Octane by Research Method' - there are a couple of ways to determine it.
Octane is a measurement of a fuels resistance to spontaneous ignition under compression, as already said above, not something you can add. The higher your CR, the more of it you need. Watch out for high octane racing fuels, as some of them are not petrol - Methanol is 106 octane, but you need LOTS of it flowing to get good mixture - in a car set up for petrol, it would run VERY lean, if at all.
jp

WallyP

This subject comes up about once a year.

Octane rating is a measure of resistance to preignition/detonation - period. Nothing else.

For many years, there were two commonly used methods of specifying octane ratings - Research Octane Number (RON) and Motor Octane Number (MON).

RON was the number used by the public and the auto manufacturers, and if someone just said "octane", they were talking about RON. This includes all of the literature and stickers on the earlier 928s.

MON was used by the oil industry and not much of anyone else, and were derived by a different test scheme. MON numbers were lower than RON for the same fuel, and the difference between RON and MON for a particular fuel was called the "sensitivity".

The U.S. Federal government got into the act, and decreed that fuel octane ratings would be standardized and posed on fuel pumps and on cars. No problem - except that for some weird reason decided to invent a new standard, not used by anyone else in the world. This is (R+M/2), which is simply the average of the RON and the MON.

(R+M/2) is always lower than RON and higher than MON. This means that if you are looking at literature for an older car, and it just says "octane", it is referring to RON. This will always be a higher number than the (R+M/2) that you can safely use.

The auto manufacturers and oil companies have spent years trying to convince people that the best fuel for their car is the LOWEST octane that does not cause detonation.

Urban legends and wishful thinking still cause many people to waste money on higher-than-needed octane fuel.

Your 928 requires a specific octane rating, which varies from the cheapest regular to expensive high-octane. No, there is no magic table anywhere on the web that I know of that gives all of the ratings, and I wouldn't trust it if there were.

Look at the fuel door - all later 928s should have the rating there. Earlier cars have it in the Owner's Handbook. Don't have the Owner's Handbook for your car? We (and the other vendors) sell them . They are either $19.28 or $21.16 from us, depending upon the year model. Call Jeannie, at (828) 766-9280.

Dozman

I appreciate all the input here. once again the 'Ole" trusty owners handbook speaks 'Loudly' again.

I guess I should spend a little more time in the books. <img src="graemlins/icon107.gif" border="0" alt="[icon107]" />

John D.

V-Fib

As a Geezer, I would like to say say...I sure miss "Ethyl".

Anthony Tate
79/928 Silver Metallic