onehdeagle

Would 100 octane fuel have any negative effects on a LS3?
How about mixing it with a lower octane such as an 89/91?

photoguy

That is aircraft fuel?? I wouldn't advise using it in an LS3 or any other engine.

NYC6

If your engine is stock the higher octane is of no use other than burning your money.

shopdog

If it is no lead fuel with the proper detergent additives, the fact that it is 100 octane won't hurt the car (won't help either, of course, the car is perfectly happy with 93 octane fuel). The car's ECM will compensate for the harder to ignite and cooler burning high octane fuel.

But don't use any leaded fuel, or any fuel that doesn't have the proper amounts of detergent. Leaded fuel will poison your oxygen sensors and cat converters, leading to rough running, overheating, and increased emissions. Insufficient detergent will let the fuel system varnish up.

AirBusPilot

No negative effects as long as it's unleaded automotive fuel. If you're going to track the car it wouldn't hurt to mix a few gallons if the highest octane pump gas you can buy is 91 like we have here in phx.

TBD

Why, pray tell?

Peace, out.

keith5

I recall that LS2 and LS3's are built to a naturally aspirated combustion at sea level for a 93 octane. Meaning that the physics dictate the compression ratio, ignition timing given the atmoshperic pressure.
You can't just change one of these variables. If you change one you must change the other two in order to realize a power gain.

Going to a 100 octane will only yield a max 93 octane performance gain.
Except that 100 will not completely burn in the combustion cycle. (once again it's a pure physics properties problem). You will end up with unburnt fuel in your exhaust system. That can lead to some "oh-****" moments with the cat or the mufflers. Booms or fires. Usuallly both

saplumr

What do you expect to gain from buying 100 and mixing with lower octane?

Daytona Bob

Maybe I can help...

The octane rating of a spark ignition engine fuel is the detonation resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same detonation resistance as the described mixture.

Octane rating does not relate to the energy content of the fuel. It is only a measure of the fuel's tendency to burn rather than explode

In most countries (including all of Europe and Australia) the "headline" octane rating, shown on the pump, is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, is 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and some even deliver 98 (RON) or 100 (RON).

It is possible for a fuel to have a RON greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, AvGas, LPG, and alcohol fuels such as methanol or ethanol can have octane ratings of 110 or significantly higher - ethanol's RON is 129 (MON 102, AKI 116). Typical "octane booster" gasoline additives include tetra-ethyl lead, MTBE and toluene. Tetra-ethyl lead (the additive used in leaded gasoline) is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that start the combustion, thereby delaying ignition, leading to an increased octane number. Unfortunately, since it is a compound of lead and hence poisonous, its use has declined since the 1970s. In the United States and most of the industrialized world, the use of tetra-ethyl lead is restricted to aviation gasoline.

So if its unleaded - your okay. You can mix it with other unleaded types.

JJC5

100 octane aviation fuel is leaded. Lowlead but it's still leaded and should not be used in automobile engines. The cats and the plugs will suffer big time.

TJBlaylock

My dad ran plane fuel in his chain saws for 20 out of 40 years as a log faller in oregon chain saw yes car no, no need.

HOTRODSRJ

Don't forget intake air temperature! That too has an overall effect. You can run lower octane in the winter vs summer easily with the same results just due to the intake temps.

onehdeagle

#1 We are at about 4500 feet above sea level.
#2 There aren't any stations that sell 93 octane.

OregonC6

I used to pull up to the pump in the late 60s in my 68 SS396 Camaro and get 100 to 103 octane leaded. Same as present day aviation fuel. The big block loved it though would still knock at times on really hot days.

drtli

As altitude goes up there is less oxygen per liter to cause compression detonation so octane requirements decrease. At 4000 ft where I live, 91 octane=93 octane at sea level. At 12000 ft you probably would not knock on 83 octane. Only exception is if you have a turbo/supercharged engine , then altitude doesnt count as much and higher octane would be required. Premium at the pump sold at your altitude has equivalent antiknock of premium sold at any other. The oil company does the math for you and sells what you need. Just buy premium!

photoguy

This is true. I fly single engine aircraft and I have to lean the oxygen as altitude increases.

dpigguy

If its unlead auto fuel, it will run but it is not needed as others have said. As far a avgas is concerned, used it in racing dirt bikes (2-stroke) and only issue is that it burns hotter then regular pump gas which in turn caused issues on longer races, etc. Wouldn't try in a LS3 for same reason let alone rest of problems it could cause with cats, etc. jmho

freyke

AirBusPilot

I think you mean you have to lean the fuel.

cclive

100LL aviation gas is leaded and will damage things in a car engine that needs unleaded. Car engines since 1975 have needed unleaded because of catalytic converters.
Also, the higher the elevation, the less tendency there is for detonation. This is why 93 octane is rarely seen in the mountain west...it isn't needed. There is nothing inherently 'better' about higher octane fuel, it is only more resistant to detonation or 'knock'. Once the octane rating is high enough to stop the knock, a higher rating will do nothing. It is a good way to waste money though.