89 octane -- what's the point?

[scheides]

So either you have a car that can run 'regular' 87 octane gas, or something that requires premium. Why do they even offer 89?

[Pushit2.0]

To make more money, my Wifes parents were a regular 89 octane purchaser until I told them your car will get better millage and run better on 87 octane. Thats what it was tuned to run off from the OEM, as far as I know there is no car that says 89 octane recommended/required.

~John

[Kracka]

John's right, its a marketing ploy and it works on a lot of people!

[xveganxcowboyx]

I just read that the 89 octane gas is just over flow from the low and high octane tanks and it's octane rating can change depending on which one over flows more. Anyone know anything about that?

People don't know much about octane. I just had a guy tell me (long time manager of a parts store) that he's one hundred percent sure his stock internals carb'd 350 runs much better on 100 octane so it's all he puts in it.

[Shane55113]

Its the 91 and the 87 mixed together literally they have hoses from each tank Y into the 89 pump handle. Just ask Gofastman, he works at a independent shop that sells gas and his boss showed him.

[turbotalon1g]

^nice.

[carltalon]

Originally Posted by Shane55113

Its the 91 and the 87 mixed together literally they have hoses from each tank Y into the 89 pump handle. Just ask Gofastman, he works at a independent shop that sells gas and his boss showed him.

This is what I've heard too. There is no 89 tank the 87 and 91 just mix in the pump to make 89.

[asshanson]

Not true in Iowa. 89 is the only gas with 10% ethanol in Iowa and it's a dime cheaper per gallon, which is why everyone there buys it. However, even with the cost savings, you're still up in the end if you buy the 87 because of mileage increases.

[gofastman]

Originally Posted by slowboy

Not true in Iowa. 89 is the only gas with 10% ethanol in Iowa and it's a dime cheaper per gallon, which is why everyone there buys it. However, even with the cost savings, you're still up in the end if you buy the 87 because of mileage increases.

thats true also, some times they just jack up the ethanol content to raise the octane to 89 but usually they sell it at the same price as 87 if they is the case, at least in MN
interesting fact, btw, my boss makes about $175 on an $18,000 load of fuel

[Goat Blower]

A lot of my cars specify 91 octane or better, but I always run 87 octane, works just fine. If you can make use of better octane gas by running more boost and/or timing, then it's worth it.

100 octane gas will make an old carbureted Chevy run better because you can advance the ignition timing without pinging. I wouldn't waste the gas though in something like that unless I was running domed 12:1 pistons or higher. Or if it had a set of T88's on it.

[gofastman]

Originally Posted by Goat Blower

A lot of my cars specify 91 octane or better, but I always run 87 octane, works just fine. If you can make use of better octane gas by running more boost and/or timing, then it's worth it.

100 octane gas will make an old carbureted Chevy run better because you can advance the ignition timing without pinging. I wouldn't waste the gas though in something like that unless I was running domed 12:1 pistons or higher. Or if it had a set of T88's on it.

the only real practical use i can think of for 89 octane is a VERY heavily loaded truck going through a hot area using close to WOT for long periods of time, it may allow the PCM to run more timing than one with 87 under the same conditions

[xveganxcowboyx]

Originally Posted by Goat Blower

100 octane gas will make an old carbureted Chevy run better because you can advance the ignition timing without pinging. I wouldn't waste the gas though in something like that unless I was running domed 12:1 pistons or higher. Or if it had a set of T88's on it.

I asked him if he'd done anything to warrant the higher octane. He said no. "It just runs better, she likes it." Then he proceeded to talk about how my "japanese import" was a waste of time.