hacker-pschorr

That $5+ a gallon was at the local pump. Track gas was over $7.

We ran "low lead" Av-Gas in my friends Corvette when he raced in NASA. From what he told me, they are only supposed to sell it for aviation purposes (like farm Diesel which gives off a special color in the exhaust). He has a huge toter-home with a stacker trailer. He would pull up to the local airport and say the plane is in back, just need gas and would fill up a 50gal.

Too many projects, the 79 needs a trans rebuild before I go back to the track. This was going to be the year then my 80 hit a deer and that become my priority.

Four of us were going to make RA Memorial Weekend this spring, now it's only Andrew.

MainePorsche

Thanks Guys.
Interesting discussion here.

Wisconsin Joe

A couple thoughts/comments:

AvGas comes in a few different grades. It's dyed to identify what it is, if it's mixed the dyes cancel each other out and it comes out clear. 80/87 is red (not a lot of lead) 100LL (LowLead) is blue. It's "lower" lead, but still has about half of what old "leaded" auto gas had. 130 is green and has about twice the lead as 100LL. There are others, but I'm not aware of them being readily available in the US (130 is pretty rare).
It's been a while since I messed around with AvGas, though. The Cessnas I've flown recently (at least in this century) were all STC'd to run auto gas.

Running leaded AvGas, or any racing gas on the street is illegal. There are a variety of reasons, one of which is that there isn't any road tax on them. Chances of getting caught are small, but still there.

As far as running E10 to reduce knocking: Octane is octane. 91 pure has the same anti-knock properties as 9 E10. It's just that the base gas in the E10 can be lower octane, with the ethanol making it "better."

Fogey1

+1

The Owners Manual for my US '83S has a whole page dedicated to the octane needed for the car and the meaning of the ratings (averaged RON & MON) shown on US pumps. All the pumps show the averaging equation, too.

I feel no guilt about using the octane rating the factory says is needed for my (stock) car and not paying extra $$ for "Premium."

will

mike77

This is specific to UK fuel but the advise from Porsche is fuel with 5% ethanol not 10%. That means premium here in the UK


http://www.porsche.com/uk/aboutporsc...-05-23-classic

GregBBRD

I would not give either of these fuels a second thought, on a stock 928.<br /><br />Except for a turbo charged 4.5 liter built in the early '80's (lasted about 10 miles), I've yet to see a 928 with a damaged piston or even damaged ring lands from detonation. Even naturally aspirated race engines which ran on lower octane than they should have been are included in this.<br /><br />Flattened, spun, or lost their crush soft stock rod bearings from the piston pushing the rod back down the hole (too much cylinder pressure BTDC) I've seen plenty of.........Way too much of, actually.<br /><br />I believe the cylinder heads have very good cooling capacity and "absorb" short periods of thermal abuse before the piston damage occurs.<br /><br /><br />

GlenL

Well, I've had broken lands and rings on my engine. Or engines, I should say. Then I got special rings and ran the octane up. So far, so good. Ascribing it to detonation is a further step, but that's the typical cause.

GregBBRD

Stock engines?

GlenL

Yes and no. The first one was a stock '80 Euro S. That had broken rings and lands. The second was (and is) a 98mm overbore with shaved heads. Higher CR. Broke just the rings on that one. I think it happened on a 200 mile trip where only 91 was available.

Now I'm running aftermarket "turbo" rings and always run with high octane. I've got a trailer rig, too, to get it to the track.

Petza914

The stations around me offer 91 Ethanol free and 93 with up to 10% ethanol.
For the forced induction subset of us reading this thread, I attended Jake Raby's M96/M97 engine building school in GA last year and asked him & Tony Callas (of Callas Rennsport) this exact question since both my 997 and my 928 are supercharged. With a forced induction engine, the answer was a no-thought-required "use the higher octane 93 even if it has up to 10% ethanol" as the higher octane helps to prevent detonation under boost.

leiplouis79

Gentlemen - please check out a company called Race Gas(orange and white can) . Can be purchased at many suppliers - Summit, Jegs , on line. It really works ---and add and adjust your octane to a decent level - up to 105. I've been using it for a while and I can tell you, my 79 is running better than it ever has - even idles much better- this is not a snake oil - its a true addtive to boost the octane level of pump gas. Found out about it, at the PRI show in Indy a few years ago.

GlenL

I have. It's a good option but costs more than getting race gas.

Adk46

When I went to California to drive home with a 987.2 Cayman, I was surprised that it's very difficult to find higher than 91, of any sort. Headed east, there was a state or two where premium was only 90. We must have some members in those states who might comment.

My practice is to use whatever premium I find during the season, but try to fill up on ethanol-free prior to winter storage. I have no justification except a weak "why not?"

MainePorsche

So I think I'm understanding here that there is no issue, or specific complication, in using a reasonable octane fuel with ethanol just don't store or let sit for long periods with the ethanol mix.

Wisconsin Joe

Higher altitude. The lower atmospheric pressure prevents detonation to a certain degree.

Pretty much. Although the "long periods" is subject to some debate.

We had a bit of a debate about "phase separation" a little while back. That's when the alcohol absorbs enough water that it separates out from the gasoline.

I don't know exact numbers for it to happen, but (as I noted above) I would fill up my old Blazer in May or June, drive it a bit and let it sit (not best practice) over and over for a couple months, and then fill up again in August or so.
Many, many 'warm & cool' cycles with lots of chances for condensation.
No problems that I ever noticed.