Gas additives?

[Birmingham Bill]

In your opinion, are gas additivies (high octane) needed to help my car run smoothly? I have a 90 911. If so, how much do you recommend per fill-up?

[Steve@Rennsport]

Bill:

Octane boosters are a total waste of money and besides, they make a mess inside the engine as well as attack the elastomers in the fuel system.

If you require more octane than pump gas, use unleaded race gas. Your 93 premium should be fine unless you have a poorly done chip.

[pwd72s]

During the winter months, I do use Sta-Bil. Injector cleaner once a year or so, tho I dunno if it's any real help.

[Lukesportsman]

Really, Steve? A recent magazine article tested a fewer of the better "accepted" octane boosters. They used both the "new" method of testing and the old carbeurated piston engine to test octanes. There was no evaluation to other characteristics you mention, but they each did raise the octane nearly their advertised 2-4pts from the CA 91 octane premium.

I don't know if it really makes a big difference but I run some 104 octane booster on top of the 93 pump in my OEM supercharged application when at the track. I don't run it in the race car, though ( I guess there is still a part of me that doesn't fully trust it).

Not that Steve's opinion needs support, but I do not feel that a stock Porsche is going to need over 93 octane without boost.

[RoninLB]

Originally posted by Lukesportsman

each did raise the octane nearly their advertised 2-4pts from the CA 91 octane premium.

2-4pts means 91.2 - 91.4, I think.

[dd74]

Originally posted by Lukesportsman
...A recent magazine article tested a fewer of the better "accepted" octane boosters. They used both the "new" method of testing and the old carbeurated piston engine to test octanes. There was no evaluation to other characteristics you mention, but they each did raise the octane nearly their advertised 2-4pts from the CA 91 octane premium.

Can you post that article, or at least tell us the magazine in which you read that report?

Thanks.

[Steve@Rennsport]

Hi Luke:

There are several issues to think about when using octane boosters,....

1) Cost per octane point.

2) Potential damage to rubber lines, O-rings, and seals in the fuel system
as well as the deposits these products leave on piston crowns, combustion chambers, and plugs. Its not pretty.

3) Inconsistent mix (octane levels) in fuel tank.

Personally, I see no harm in carrying a bottle of 104+ just for emergencies where you might have accidently received something other than premium gasoline. Thats not as uncommon as you might think.

I simply try to discourage people from using such products in lieu of 100 octane unleaded when possible.

Ultimately, its your dime,...

[Don Plumley]

Originally posted by Birmingham Bill
...are gas additivies (high octane) needed to help my car run smoothly? I have a 90 911.

As your question reads, my assumption would be that you should not need octane boosters to help your car run smoothly. Unless you have a real gas quality problem, your engine is designed to run on 91 octane fuel.

What's not running smooth about it?

I have an 87 with a more primative DME, and I run fine on our legendarily bad CA gas.

Don

[mschuep]

My manual says no less than 92

[KobaltBlau]

note that the manual is probably referring to RON while our gas is rated as (RON + MON)/2. These come out a few points different.

[tobluforu]

If you have a supercharged car or a turbo, porsche or not, try a product called torco. I have no idea what's in it, I have no idea what it does to the internals of the engine and what not, it's expensive as hell, but it works. When I dump this stuff in the sc viper I notice a difference right off the bat, but you have to pre-mix it. These things are kind of like band aids in a sense. If your car is put together right, tuned on a dyno then there is no need. But if your looking for a little more pep, then give it a shot. Useless on a na car.
http://www.torcoracefuels.com/catalog/product_info.php?products_id=29

[sammyg2]

Yep, an octane booster that is advertised to raise the octane 4 points will increase it .4 octane as stated above, it will not raise it from 92 to 96.