yardpro

i have been over this time and time again with the race bikes we used to run.

We are talking about 250cc (1/4 litre) producing 50+hp... VERY high performance 2 stroke, then later extremely high performance 13K rpm 4 strokes....

We used to get a kick out of the guys that would come to the track with their jugs of vp112... 112 octane race gas.. on a stock motor..

As coreman pointed out, higher than required octane actually reduces power as it is harder to ignite.

The ONLY benefit to running higher octane is that you can run leaner, and/or more compression..both of which make more Hp.....
basically higher octane allows you to run a better tune on a motor. that's it.

you will make the most Hp with the lowest octane that will not detonate.

docmirror

I used regular in my GT for many years. In TX, no detonation problems. The detonation margin is controlled partially by the seasonal mix of the fuel. If you put winter regular fuel in and leave it through summer, you might have a slight issue.

I don't think premium is worth the extra cost. My only reason for ever using it would be the better energy of non-Ethanol which can make a decent difference in either economy or power.

Rod Underwood

Regular and Nitros would be like diet cokes with your five pieces of double chocolate cake. ;-)

Rod

Sorry I missed the ride at Sharks.

Barry Chan

so yesterday went fill up with 91 octane and ran for a while and so far so good, all i know from this experience (for my car) is regular doesn't work for MY84, my wife's ford windstar also requires mid-grade or higher or it will ping. The gas in US maybe 20 cents a gallon between regular and premium but in Canada is 20 cents a liter between the two so 80 liter is $16.00 a tank!!

James Bailey

Barry it is also possible that your ignition advance (set by hand at the distibutor) is not at factory specifications which could increase the possibility of "pinging". It would still be an interesting experiment if you had your wife fill the car and not tell you which grade you are burning when. Do it 4 or 5 times before you compare your notes with her notes about the grade of fuel that was actually in the car.

hacker-pschorr

Could also be a bad tank of gas, this happened to my 944S and I always ran 93 in it.

Ran like hell until I flushed the tank.

cali4sun

Avoid Ethanol When Possible

Gasoline that has been cut with 10 or 15 percent ethanol, called E10 or E15, is an mpg killer. Why? Gasoline stores more energy than ethanol (119,000 Btu per gallon vs 80,000). So it takes more ethanol than gasoline to go the same distance.

'89 S4 GP White/Black
'76 912E Silver/Black

fbarnhill

Yes, no Ethanol. I put 370k miles on my 83s and most of it was using regular. Using 92 or 93 would make a small difference in performance but for every day driving, I just could not see the value in the more expensive gas. I could not tell a noticable difference in the mileage either. Maybe on the later cars it will make more difference...

Just my .02 cents worth...

xschop

Ethanol + Hydrocarbons = Organic Acids

The Ethyl alcohol doesn't attack the newer N-buna fuel lines, but the acids do and whats worse is the severely high reaction of organic acids with NIkasil. Don't leave that crap in your tank over long periods of time, avoid it if at all possible.

Barry Chan

My mechanic told me to set the distibutor to where the knocks stop.
we have tried a few times with regular gas in her van and it pings up the hill but no problem with mid-grade.
I will try the regular gas from another station and see.
just how would i know? sign on the pump?

davek9

Yes me too, I looked for you Saturday night, Gary Knox went for a ride and so did a few others; they all got out of the car with big smiles on the faces.

ilikebig928butts

*Freshman* '84 928S chiming in:

Any of the 78-84'rs run on 89 octane? I see 87 and 91 mentioned throughout but not a peep on 89. I'm considering 89 as I *just* got my 1st 928S a month ago. I had no freaking clue that it ran on 87 until the venerable Jim Morehouse sent me the missing owner's guide.

Bill Ball

Love your user name. LOL!

Be sure to join our local group (See below).

dcrasta

@Barry > From what I could find, Ford recommends 87 Octane in Windstars (per 1996 Owners manual).

I would not recommend setting the timing without the use of a timing light. The factory timing spec should be on a sticker under the hood or in the Owners manual. I found a copy on scribd.com
[ http://www.scribd.com/doc/8950544/19...-Owners-Manual ] Information I found says this cannot be adjusted as the 3.8 ford uses wasted spark ignition timing (no dist). Your car may be different (no first hand experience with fords) and if there is a distributor I would not adjust without a timing light.

James Bailey

I think he is adjusting the 928 ignition timing by ear.....and finds it "needs" higher octane fuel....