Octane Question

[londonontman]

I recently had a customer come into my store and asked that since he has to run premium gas (91 octane) could he run an 89 octane (which is cheaper by almost 15 cents a litre here) and add an octane boost to bring it up to a 91? I honestly couldn't answer this one....what do you all think

[00Beast]

Unless it's that special canadian octane booster, most octane boosters don't do anything measureable. An octane booster that claims 6 points raises octane from 89 to 89.6. Not worth it, IMO.

[londonontman]

Actually it was a NOS product that "claims" a 5 point increase so his thinking was 89+5=94 octane

[willwren]

No, 5 points is .5 octane. Each 'point' in an octane booster is 1/10 of an octane.

Gets pretty expensive that way, doesn't it?

[londonontman]

Figured it was best to ask since I honestly didn't know. Thanks everyone.

[willwren]

If you simply used 89, you would have reduced ignition timing and reduced power and mileage. The reduced mileage would offset the extra cost of premium. It's a wash financially, so it's best to run the premium and prevent long-term engine damage.

I lost a motor due to an error by a pump jockey (we don't pump our own fuel in Oregon).

[repinS]

(91 octane) could he run an 89 octane (which is cheaper by almost 15 cents a litre here)

The difference between regular 87 and premium 91 is 13 cents here, not sure where you're getting 15 cents between 89 and 91.