Current Events > Does gasoline octane rating work this way? Question for car fanatics

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My car says 91 octane rating is recommended. Can I do half 93 octane rating and half 89 octane rating to equal 91 and save some money? Or is octane rating on a weird logarithmic scale or something and isn't a simple addition and division to get 91?
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ask yourself, does that really seem like a good idea?
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J E S U S posted...

ask yourself, does that really seem like a good idea?

Uh it doesn't sound like a bad idea. Just asking if it'll hit the 91 octane rating.
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ChainedRedone posted...

J E S U S posted...

ask yourself, does that really seem like a good idea?

Uh it doesn't sound like a bad idea. Just asking if it'll hit the 91 octane rating.

the 91 is actually partially mixed at the pump. most gas stations only have the 87 and 93 and when you get the 91 they mix the two of them in real time as you're pumping.

But I don't know what the ratio is, neither do you, you don't know exactly how much empty space you have in your tank, either.

So while yes it works in theory, it's not a good idea.
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ChromaticAngel posted...

ChainedRedone posted...

J E S U S posted...

ask yourself, does that really seem like a good idea?

Uh it doesn't sound like a bad idea. Just asking if it'll hit the 91 octane rating.

the 91 is actually partially mixed at the pump. most gas stations only have the 87 and 93 and when you get the 91 they mix the two of them in real time as you're pumping.

But I don't know what the ratio is, neither do you, you don't know exactly how much empty space you have in your tank, either.

So while yes it works in theory, it's not a good idea.

Yeah that's what I was wondering. If the mix is actually an equal (93+89)/2
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ChainedRedone posted...

Yeah that's what I was wondering. If the mix is actually an equal (93+89)/2

That I don't know. The answer is probably not. It's probably not far off that.
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what car do you have? if its a modern car there is a good chance it will just retard the timing and slightly reduce performance if you go just straight 89 octane.
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Put in whichever one doesn't have ethanol.
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KILBOTz posted...

what car do you have? if its a modern car there is a good chance it will just retard the timing and slightly reduce performance if you go just straight 89 octane.

Pretty much this. The engine won't run efficiently, so you'll probably lose some MPGs which negates any savings you were trying to get by going with a lower octane.

Me? I go with 93 (car asks for at least 91) because I'm not a cheapskate.
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Super Saiyan 3 Goku posted...

KILBOTz posted...

what car do you have? if its a modern car there is a good chance it will just retard the timing and slightly reduce performance if you go just straight 89 octane.

Pretty much this. The engine won't run efficiently, so you'll probably lose some MPGs which negates any savings you were trying to get by going with a lower octane.

Me? I go with 93 (car asks for at least 91) because I'm not a cheapskate.

It's recommended for 91 you don't get any benefits if you go above what the manufacturer recommends because the engine wasn't designed to optimize at those ratings.
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ChainedRedone posted...

Super Saiyan 3 Goku posted...

KILBOTz posted...

what car do you have? if its a modern car there is a good chance it will just retard the timing and slightly reduce performance if you go just straight 89 octane.

Pretty much this. The engine won't run efficiently, so you'll probably lose some MPGs which negates any savings you were trying to get by going with a lower octane.

Me? I go with 93 (car asks for at least 91) because I'm not a cheapskate.

It's recommended for 91 you don't get any benefits if you go above what the manufacturer recommends because the engine wasn't designed to optimize at those ratings.

That's true, except that 91 octane isn't available where I live - only 87, 89, and 93. Believe me, if 91 was available, I'd run that.
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