What do you do when 93 Octane is not Available?

[wgerow]

Kinda getting my learn on about ROW euro cars, primarily 84-89 3.2 cars. One thing I have seen several times is folks saying their car is set up to take 93 octane. In many states this is no longer available. So what do you do??

Is 91 a major no-no in these cars?

Do octane boosters work? Some say no.....some say they use them

Are there economical mods that can be done to limit damages from using 91?

Do the mods limit the HP/performance of the car?

Thx

[Tippy]

Octane boosters are snake oil.

Maybe get a computer chip from Steve Wong who makes a 91 octane friendly fueling map and enjoy instead of worry.

[Reiver]

91 is fine. The European rating is diff than the US. Check it out and you'll find that compatbility is easier than you think.

[Drisump]

My Euro seems to run fine on 91, but I run 94 locally, however on tours it isn't always available...so 91 it is.

[Eagledriver]

91 should be fine. We have race cars with Euro pistons that run 91 octane.

-Andy

[porwolf]

Maybe this helps: From my original '79 manual:

[FrenchToast]

Originally Posted by wgerow

In many states this is no longer available.

Thx

Which states!??!?!?!?!????!?

EDIT: Been corrected by Quicksilver and JavaDog below. Thanks guys!

Take care!

[wgerow]

Originally Posted by FrenchToast

Which states!??!?!?!?!????!?

California and Maine for sure.....there are others. Appears to be harder and harder to find in some states.
93 Octane Gas - Locations Across USA - Page 5 - Corvette Forum

[wgerow]

Originally Posted by porwolf

Maybe this helps: From my original '79 manual:

Thanks
Mostly talking about euro cars, which didn't have a cat., but had a pre-muffler. Yes, maybe they were/are supposed to have a cat. installed as part of Federalization, but many have been converted back to their roots of a euro spec beast

[javadog]

Whether or not the car has a catalytic converter isn't the issue. The engine compression ratio is the main concern, along with the fact that in some areas of the country we experience much greater temperatures than they do in Germany. A 1979 SC doesn't have a high compression ratio and can burn about any gasoline blend. A ROW 3.2 is a different beast.

I don't know what the fuel octane requirements are for a normally aspirated 3.2, offhand. If it's higher than you can buy locally, either setting the fuel quality switch in the Motronic ECU to position 4 or having a custom chip burned for you would seem to be two options. I have experience running a ROW 930 which was intended to use 98 RON fuel and reducing the timing on that car was one way of dealing with the problem.

People are used to thinking that you can deduct 4 octane points from a RON value to arrive at an equivalent R+M/2 value, but that's not strictly the case.

JR

[FrenchToast]

Originally Posted by javadog

Whether or not the car has a catalytic converter isn't the issue.

Yep. Cats only come into play when you're deciding between leaded and unleaded fuel. A car with a cat you can't put leaded fuel in. However, not all cat-less cars can take leaded fuel either. Now cars with dogs, that's a different story.....

It was around 1979-1980 when catalytic converters started to become mandatory for U.S.-sold cars. One of the reasons the 930 was pulled for the beginning of the eighties.

Guess I should be glad here we can still get 93. Wish we could get fuel without any effing ethanol though.

Take care!

[Quicksilver]

Originally Posted by FrenchToast

Which states!??!?!?!?!????!?

I'm no fuel expert, so follow what others say. However, higher octane fuel typically improves performance in most EFI gasoline/petrol cars. From trucks, cars, etc. plus modern day ones. There are obviously exceptions, but on most it will advance the timing. It is very noticeable when towing with a truck, newer ones as well.

However, when doing any track days or anything, I wouldn't recommend anything lower than 93.

Take care!

Increasing the octane will only improve the performance on a car with a knock sensor. The 3.2s don't have knock sensors so any extra octane doesn't do anything to improve performance.
The only appreciable improvement may be that some brands have improved additive packages for their premium gas that may keep injectors clean to help with long term reliability.

... Or you could put in some Seafoam every once in a while.

[javadog]

Originally Posted by Quicksilver

Increasing the octane will only improve the performance on a car with a knock sensor...

... only if the current octane is insufficient and causing detonation, which then causes the computer to reduce the timing and thus also reduces the torque.

If there is no knock and the timing is not being reduced, increasing the octane will likely reduce power slightly.

JR

[Eagledriver]

While the Euro Carrera has pistons that are quoted as 10.3 compression ratio, they are actually less. For some reason Mahle quotes their piston CR based on zero deck height. Actual measure CR is usually .5 less. So the Euro Carrera actually has 9.8 CR.

-Andy

[1derbar]

I have a 1981 911SC and I use 89 octane. 93 is not available in Maine. With every tank of gas I add Marvel Mystery Oil, 104 octane boost, Lucas upper cylinder lubricant and Marine Sta-bil. My mechanic swears by the recipe, and the car's been running great! I do not have a catalytic converter, and I can get 100 low-lead at a local airport, but I'm not sure if that would be good for the car. Anyone know?

[Quicksilver]

Originally Posted by 1derbar

. . .
I do not have a catalytic converter, and I can get 100 low-lead at a local airport, but I'm not sure if that would be good for the car.
. . .

AV gas has a different specific gravity then auto gas and a different vapor pressure. You should expect it to require different mixture settings to run correctly.

It probably won't directly cause any major havoc but I don't like to use "probably" as a guideline for the care and feeding of a motor that costs $10k to rebuild.

Originally Posted by 1derbar

. . .
With every tank of gas I add Marvel Mystery Oil, 104 octane boost, Lucas upper cylinder lubricant and Marine Sta-bil.
. . .

BTW - If you have a stock US market SC then 89 octane is fine. All the other stuff is just helping the cash flow. STA-BIL is a good idea if the car is driven infrequently. Other then that just buy a quality gas that has a good detergent package. Chevron and Shell are good choices.

[Eagledriver]

Do not run 100 LL in your car. The lead makes white deposits in your combustion chamber and can cause sticking rings.

-Andy

[Tippy]

Quote de Quicksilver

Increasing the octane will only improve the performance on a car with a knock sensor...

... only if the current octane is insufficient and causing detonation, which then causes the computer to reduce the timing and thus also reduces the torque.

Carrera 3.2 electronics wouldn't know if the engine is detonating - thus no retarding of timing.

[Juggino]

Just go to any auto supply and buy NOS octane booster, should add about 7-9 more octane even though it says 10.

[GH85Carrera]

Just don't worry about it. There is almost no 93 in Oklahoma. I can buy 100% gas no ethanol, but 91 is about you can find. It has never been an issue in 16 years of driving.