6mil928

That sounds right. 87 was horrible. Id been using 89 exclusively prior. Jason

jheis

"Fuel Recommendation
....
Minimum octane rating is 91 RON (87 CLC rating on U.S. fuel pumps).
....
The CLC octane rating is usually 4 points lower than the RON rating:

91 RON equals ................ 87 CLC
95 RON equals ................ 91 CLC"

928 OWNER'S MANUAL
MODEL '82
page 63

ROG100

I run regular 87 in my pre 82 US cars with no problem.

6mil928

Any other experts want to chime in

I have no idea what the facts are anymore. I think I'm gonna run what my car seems to like no matter what that may be.

R.Pires

Hi,

I can't vote on this poll because here in Portugal we only have two options, 95 and 98 octane fuel.
Of course I only use 98 in my 83 S, as recomended by the owner's manual and the sticker near the fuel filler!

Regards

Dennis Wilson

US pumps use M+R/2 which is the average of both ratings. i.e. 87+91/2 =89.

Dennis

6mil928

I've heard this before that they mix 87 and 91 to get the 89. Is that what your saying?

hacker-pschorr

Using the word explosive is the only issue I have with Lizard's post. But since I know what he was trying to say, it's a non issue.

Lower octane does burn faster, he is dead on with this statement. High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.

This isn't rocket science and blasting Lizard for mis-using one word is a bit unnecessary.
Simple rule of thumb = run the lowest octane you can without knocking.

A low compression engine like the US 16V (I'm not sure the real CR of the 83-84 cars so that's up in the air) with the very tame ignition curve in theory will be just fine with 87.

Factors that get in the way:
Age = carbon buildup, creates hot spots and in a round about way raises compression ratio

Quality of parts = Running the correct spark plugs? How good are the wires, rotor etc.... I've worked on ill running cars "fixed" by installing the correct OEM parts versus "high performance" aftermarket.
My friend has a 1.8t VW he's always putting **** aftermarket parts on (he falls for all the ads). His car was idling funny and knocking like crazy on the upper end. He put in some $20 a piece go fast spark plugs. After putting in $2 Bosch Coppers his problems went away.

Quality of gas, go to BFE and fill up on 87 that's been sitting there for 8 months..... This is why I stay away from "off the beaten path" gas stations if I can.

So.....
If your low compression motor has clean cylinders / pistons, timing is stock, all parts are in good working order, valve guides / seals are not leaking etc..... good quality 87 octane will be fine.

I'm curious how many people pull their spark plugs on a regular basis to check for detonation.


On a side note, I run 87 in my 79 track car The motor is 100% stock except for exhaust. 8:1 (or less) compression has it advantages on the weekend budget.

6mil928

Just did mine and no sign of detonation. Only half issue was one bank was getting more fuel than the others by the look of the plugs.

Dennis Wilson

What I am saying is that CLC is the old standard used in the US and RON is the standard used in Europe. Now, US pumps rate the octane based upon an average of the two standards. i.e. M(CLC)+R (RON)/2=the new rating used in the US. BTW there is an older thread here that explains it much better than I could.

Dennis

hacker-pschorr

Each bank does have it's own fuel pressure regulator. At least the stock ones do

LightStriker

1980-81-82, they are 16v no?
As far as I know, the US ran on 9:1 ratio, and Europe ran on 10:1 ratio.
1984-85-86, ran on 9.3:1 (US) and 10.4:1 (Europe)

Next what? You will tell me that dull black car cannot be picked by laser and radar?

6mil928

That's correct Hacker. It's one of the projects that are on the back burner till the more pressing issues are resolved.

Dennis Wilson

As far as I know, the early US and ROW 928's had the same spec's even though the ROW 300HP engine may have had a higher compression ratio.

As far as I know, your statement is generally wrong.

As far as I know, saying "as far as I know" doesn't give you the right to insult anyone.

Bye, as far as I know.

Dennis

LightStriker

Well, those infos come from the Porsche 928 Workshop book.
So, if they are wrong, I would like to know! Cause I was expecting that thing to be correct.... and I'm basing my repair on it!