Octane Recommendation?

[bonsaiwino]

W e just got a '79 carbureted Spider. What fuel octane should I run? Thanks!

[Exit98]

Save your money. Regular is fine.

[aj81spider]

I agree with Doug. When I first got mine I ran premium - then I tried an experiment with regular and noticed no difference at all. I've been running with regular for over a year now.

[Dawgme85]

I find that SHELOB runs best on Ethanol-free fuel, regardless of Octane rating. I typically run 89 Octane (mid-grade), even though 87 should be sufficient, given the low compression ratio of the stock pistons.

YMMV

Maybe I'll try running regular, instead...

[spidernut]

Fiat specified premium fuel. My 79 will run on any octane without pinging. I run mid-grade in the People's Republic of California because I seem to get slightly better fuel economy.

[So Cal Mark]

for best results, use the lowest octane fuel that doesn't result in pinging

[Alleycat124]

Does anyone run regular fuel with a treatment like Lucas?

[AriK]

Does anyone run regular fuel with a treatment like Lucas?

Alleycat,
There are still some stations left that offer 0% Ethanol. Ethanol is a fuel system killer on older cars. It attracts water and is harmful to our carbs and metal fuel lines. It is so corrosive that the gas companies only add it at the stations so to avoid rusting their own pipelines. It eats rubber fuel lines, in fact you need to upgrade them (including your fuel filler hose) for conformity. If it sits too long in your tank and lines it curdles, or in other words transforms into semi solid composition, thus needing to blow out your lines before startup. It also holds less energy content than the same amount of real gas. A 10% ethanol fuel adds up to about 3% energy loss on old cars. A new car's ECU advances the ignition timing and readjusts fuel mixture to compensate but our old cars, well they are just old cars trying to cope.
I try to avoid this type of fuel in my Spider if i have the choice. I do keep a stash of Carb Defender,by Driven, recommended by Mark Allison if i have no choice.
Petro Canada has ethanol in all its fuels, (no labels at the pumps) so stay away from there.


Canadian Tire insinuates with their labels that their fuel contains ethanol in regular and mid grades, but not in premium


Ultramar claims not to use ethanol in their premium brand from Ontario to Labrador.


Shell has no ethanol in their premium V-Power in all of Canada (but not in U.S)



So premium fuel it is for me from the right station. I do not choose it for the octane, in fact i get no pinging with regular.
Please note, I'm not saying premium fuel is better for cars that require unleaded, I'm simply discussing the effect of the ethanol content found in the lower grade fuels vs ethanol free premium grades.

I do however have one question for Mark Allison (or anyone else who knows), since he promotes "Carb Defender":
When i proceed with my 1000 km roadtrip to FFO next week, i will not be going out of my way to find ethanol-free fuel. Does Carb Defender have an influence on fuel that will be consumed the same day, or is it just meant for seasonal storage?

[So Cal Mark]

Carb Defender treats the metal, not the fuel. That's a major difference between it and other fuel treatments such as Stabil. As a rule, you'll get the most power from the lowest octane fuel you can run without detonation. The effects of ethanol are pretty detrimental to older cars as mentioned in a previous post. It does tend to varnish pretty quickly. We see FI cars that have been sitting for 3 months with stuck injectors.

[Frog2Spider]

So is 'Carb Defender' a fuel addititive that will clean FI systems also?

[djape1977]

avoid etanol by any means possible. it eats away fuel hoses this creating leaks and fire hazard. i've had several cars with engine bay fires at my workshop because of deteriorated rubber fuel hoses. in fact, check condition of rubber hoses in the engine bay at least every couple months. fold them over, if you see ANY cracks, or hose feels and looks gooey, change all of them.

octane? any will do.

[DieselSpider]

Unfortunately one thing you can't easily check is the rubber diaphragm in the old style mechanical fuel pumps. Ethanol eats those up too causing leaks both outside of the engine and sometime a spray of gasoline that gets into the crankcase and dilutes the engine oil causing internal damage.

On my SuperDuty truck even though its fuel injected I get 12 mpg on the highway on gas without Ethanol while on 10% Ethanol that drops to 8 mpg so even though they claim only a 3% energy loss on old cars I am seeing a consistent 20% loss of fuel economy on a fuel injected V10 truck when using 10% Ethanol. Ethanol treatment for an 80 gallon tank gets quite expensive too.

[njoconnor]

AriK asked:

"I do however have one question for Mark Allison (or anyone else who knows), since he promotes "Carb Defender":
When i proceed with my 1000 km roadtrip to FFO next week, i will not be going out of my way to find ethanol-free fuel. Does Carb Defender have an influence on fuel that will be consumed the same day, or is it just meant for seasonal storage?"

After reading this series of posts, I asked Old Friend Google for a hand. This "Pure Gas" site is now on my cell phone:

http://pure-gas.org/

Might help you on your trip! Enjoy FFO; wish I could make it this year.

I'll be switching my fuel purchases to a local place which sells ethanol free premium. This place is located less than a mile from our local Costco, which suppresses their fuel prices to "reasonable"... . After 15 years of fueling A4Q's, 900 Turbo's, and BMW 3 series with premium, I'm used to the mild hit to the wallet.

Safe travels, Ari!

Neil

[AriK]

AriK asked:

"I do however have one question for Mark Allison (or anyone else who knows), since he promotes "Carb Defender":
When i proceed with my 1000 km roadtrip to FFO next week, i will not be going out of my way to find ethanol-free fuel. Does Carb Defender have an influence on fuel that will be consumed the same day, or is it just meant for seasonal storage?"

After reading this series of posts, I asked Old Friend Google for a hand. This "Pure Gas" site is now on my cell phone:

http://pure-gas.org/

Might help you on your trip! Enjoy FFO; wish I could make it this year.

I'll be switching my fuel purchases to a local place which sells ethanol free premium. This place is located less than a mile from our local Costco, which suppresses their fuel prices to "reasonable"... . After 15 years of fueling A4Q's, 900 Turbo's, and BMW 3 series with premium, I'm used to the mild hit to the wallet.

Safe travels, Ari!

Neil

Thanks Neil! I have seen that site as well. The trip is way too long to cover in one day therefore i will not go out of my way to look for ethanol-free fuel. It will be one less stress to worry about while i'm pushing a 36 year old Fiat through such a journey. I got some Carb Defenders on special last week that i can feed the tank during my fillups.
As a side note E-0 fuel can usually be found at gas stations that share Marinas since it's general rule that boats must get E-0.

[DUCeditor]

The ethanol thing is real. Its a ridiculous political intervention. But that said older Fiat 124s don't seem to care. I've run mine on "regular" throughout the ever changing mandated formulas for 27 years.

Apart from the ethanol the biggest change in fuel is that so much of it is not "gasoline" at all. The "higher octane" anti-ping is no longer created by further distillation but by increased additives. Additives that tend to form deposits in the combustion chamber and on the valves.

We tested this hypothesis on Ducati motorcycles and found that the motors stayed cleaner AND produced better power on the lowest grade of fuel that they could run without pinging.

-don