Octane Boost to Supplement 91 Octane Fuel

[Ls1eater]

So as we all know, the C8 manual calls for 93 octane. But since that is very hard to find in the day of state emissions requirements, can we use a high quality octane boost (torco or boostane) to supplement 91 (or even 87) octane without voiding warranty or causing engine damage?

[John]

Welcome Ls1eater. A couple of things to assist you. First our Corvettes does not require 93 octane. Our Corvette motors of this and a couple of earlier generations will run fine with 91 octane. There are some Corvette motors going literally over 500,000 miles without 93 octane fuel and never needing even their heads removed.

GM does not recommend octane boosters., To salve your wallet, to save your motor, I would never use one can myself. Just enjoy your Corvette on the highest octane you can get where you are (without buying above what regular gas stations have) and not to worry a bit. On our Corvettes, we I have hundreds of thousands of miles with very rarely over 91 or 92 (best we get where I live) — never a single motor issue.

[ZonaZ06]

Unfortunately my state does not carry the recommended 93, with 91 being the highest available but with reduced performance.

I'm fortunate to have 100 unleaded race fuel available in my area and do add 2.5 gallons of 100 to a 8.5 gallon 91 fill bring the octane to 93/94.

[MidEngine]

Those are good options for those who choose but candidly other than on the race course if then and other than from time slips at the drag strip your butt dyno is not going to be able to tell the difference between your power at 91 vs 92 vs 93 octane.

[Milliwatt Rob]

Outside the West Coast, when 93 is unavailable, its due to elevation. The higher the elevation, the thinner the air. Which means, compared to sea level, engines are operating at lower cylinder pressure (except some supercharged and turbocharged cars). So your car at 3500 feet and up does not need 93.

The same is true across the board. Where 87 octane regular is commonly sold at sea level, in the mountains it may be 85.

[RKCRLR]

I agree with comment about not using an octane booster. There is a specific warning in the owner's manual about fuel additives and all of the octane boosters I've seen contain those additives.
The manual also states 91 octane is acceptable but the engine may have reduced power and fuel economy (I don't think you'd ever be able to tell unless you were running a timed event).
Don't use less than 91 octane.

[ZonaZ06]

Exact words in the C8 owners manual. 91 may be used but, "with reduced performance". 😞

[Mark2021C8]

I have used Boostane Premium in my 600 hp Mercedes AMG engine with great success. It does make a difference in power so if you can only get ahold of 91 and don't want the "reduced power" this is a good alternative. But if you use any octane boosters and you use them regularly, the one downside is you may need to change your spark plugs more often than the recommended timeframe.

Exact words in the C8 owners manual. 91 may be used but, "with reduced performance". 😞

[RKCRLR]

Here is what the owner's manual says about fuels:

Prohibited Fuels
Caution
Do not use fuels with any of the following conditions; doing so may damage the vehicle and void its warranty: .
For vehicles that are not FlexFuel, fuel labeled greater than 15% ethanol by volume, such as mid-level ethanol blends (16–50% ethanol), E85, or FlexFuel.
Fuel with any amount of methanol, methylal, ferrocene, and aniline. These fuels can corrode metal fuel system parts or damage plastic and rubber parts.
Fuel containing metals such as methylcyclopentadienyl manganese tricarbonyl (MMT), which can damage the emissions control system and spark plugs.
Fuel with a posted octane rating of less than the recommended fuel. Using this fuel will lower fuel economy and performance, and may decrease the life of the emissions catalyst.

Every octane booster I've seen has MMT in it or some other prohibited additive.

[Denizen]

Those are good options for those who choose but candidly other than on the race course if then and other than from time slips at the drag strip your butt dyno is not going to be able to tell the difference between your power at 91 vs 92 vs 93 octane.

Correct for some but not for others.

I can feel the difference when I use octane booster in another mid 400s hp car vs 91 octane alone. Maybe you can't.

If you are the sort who enjoys the "kick in the pants" feel when playing hard with your car then give it a try. If you're the sort who enjoys going slow in the slow lane and never exceeding 3500rpm then you''ll probably not feel a thing.

To thine own self be true. Decide who you are and act accordingly.

You've spent lots of money on a very high performance car. Can you live with knowing you're only getting "reduced performance" from it?

Act on that knowledge.

[Jetdriver]

I've used both and can't tell the difference between 91 and 93. Here in MO. BP sells 93 octane without ethanol added, I use it, but no change in performance from 91 with up to 10% ethanol that I can tell, since I discovered the 93 speed juice.

[meyerweb]

Performance will be reduced ONLY if the engine knock sensors detect pinging and retard the timing. In most conditions, even brief full throttle runs probably won't cause detectable pre-ignition. In very hot weather, if the engine is heavily loaded, or you're running hard enough to really raise engine temps, then yes, timing will be retarded and the difference can be noticeable, if small.

[MidLife]

Those are good options for those who choose but candidly other than on the race course if then and other than from time slips at the drag strip your butt dyno is not going to be able to tell the difference between your power at 91 vs 92 vs 93 octane.

The the octane number regarding fuel does not mean more horsepower just because it's higher octane. The higher the octane rating just means the fuel is harder to ignite, not more horsepower. Race cars use higher octane in higher compression engines or forced induction engines to keep fuel from pre igniting due to higher cylinder temps from more compression. Using high octane race gas in a regular engine will not make any more power than 91 octane, or maybe less.

[Milliwatt Rob]

But the LT1 is not a "regular engine" specifying 87 octane fuel. It is high compression engine requiring premium fuel as per Chevrolet.

If you use lower than recommended octane fuel and the knock sensors detect it, the engine will adjust ignition timing and likely also fuel richness to curtail the knocking. This will lower the available horsepower, depending on how much adjustment the computer deems necessary. It may also adversely impact fuel economy.

[meyerweb]

But the LT1 is not a "regular engine" specifying 87 octane fuel. It is high compression engine requiring premium fuel as per Chevrolet.

If you use lower than recommended octane fuel and the knock sensors detect it, the engine will adjust ignition timing and likely also fuel richness to curtail the knocking. This will lower the available horsepower, depending on how much adjustment the computer deems necessary. It may also adversely impact fuel economy.

But it doesn't permanently retard timing. Once the the knock detectors no longer detect knock, the system will revert back to the normal map.