Mid-Grade Gasoline (89 Octane)

[NickZ28]

So, I'm on my smoke break at work, checking gas prices, and it dawns on me...why do we have mid-grade gasoline? Does anybody use the 89 octone mid-grade? If so, what are the advantages of using that (and spending the extra dime) versus the 87 octane?
I use the 87 octane in our jeeps, the Vette and the SS get the 92 octane or higher. Someone please enlighten me as to why there is 89 octane gasoline....

[CleanGene]

I run 89 octane in my truck, but that's only because it's been custom tuned to run on that octane. Before tuning, I ran 87.

[Ted S.]

Maybe it's just in my head, but the higher octane the gas, the more pep my s10 gets, and the longer I can go between fill ups. I really need to actually document this one month. I had to stop using the 92 because that is all I used to use, but supposedly my engine isn't designed to burn high octane all the time (something about the engine cannot handle the higher heat that goes with the higher octane?!?!)

Now I use at least midgrade, I'm afraid to put the cheap stuff because it seems like the engine just spits it out faster, and I'm putting $20 in the tank in four days vs. the five I would get with midgrade.

[CH.Detailing]

Run the octane that is recommended by the manufacturer, or what your car has been custom tuned for, otherwise you are just wasting money!

[rider9195]

The higher the octane the less resistant it is to burn. Higher performance cars with larger engines, or ones that might have a turbo charger create more heat inside the combustion chamber. The heat might get so high that the fuel is ignited while the piston is still traveling upwards and of course over time that can cause damage. That is call pre detonation. Common on modified turbo charged cars. So if you run 87 in your 800 HP forced induction vehicle it may the fuel may pre detonate. But if you run 93 or higher, the fuel will not pre ignite and the engine will run correctly.

Run what the manufacturer recommends, it is worth it.

[FUNX650]

So, I'm on my smoke break at work, checking gas prices,

-Hopefully...
A "filling-station" is not your place of employment?!?!?!

Bob

[TimmyG]

The higher the octane the less resistant it is to burn. Higher performance cars with larger engines, or ones that might have a turbo charger create more heat inside the combustion chamber. The heat might get so high that the fuel is ignited while the piston is still traveling upwards and of course over time that can cause damage. That is call pre detonation. Common on modified turbo charged cars. So if you run 87 in your 800 HP forced induction vehicle it may the fuel may pre detonate. But if you run 93 or higher, the fuel will not pre ignite and the engine will run correctly.

Run what the manufacturer recommends, it is worth it.

Exactly. Higher octane burns slower.

I only run shell v power premium in my cars. Average 18 mpg+ in both of my 400+ rwhp cars too!

[timaishu]

Ive ran both 87 and 91 or whatever it is in my altima and have noticed no difference. On the fuel door, it mentions using the highest octaine for best performace. So Ive been using 91.

[Pockets@PoorboysWorld]

Thought it had something to do with the compression spontaneous combustion retardation as well.

In the higher performance engines they have a higher compression rate as well so you have to run higher grade or it will spontaneous combustion due to compression alone (heat as a contributor too I guess as posts above mentioned)

[dougaross]

The computers in some cars will have knock sensors and will compensate for different octane. Although I rarely use 87 and mostly use 91/93, I find little if any difference in performance.