Exceeding Recommended Octane Rating

[DEEKAYPEE8569]

Just wondering if anybody has an opinion about this.
Most cars today have recommended octane ratings; nowadays, usually a minimum of 87, for proper operation.
Does anybody else see any performance difference if they use 89 octane; or higher; in today's engines?

 

[CrashTest]

Too much octane means all the fuel won't burn so you'll have unburned fuel going out the tailpipe and blown by the piston rings. Issues? Messed up catalytic converter, messed up O2 sensors, piston ring compromise, brown stains on the side of your car above the tailpipe.

 

[DEEKAYPEE8569]

Too much octane means all the fuel won't burn so you'll have unburned fuel going out the tailpipe and blown by the piston rings. Issues? Messed up catalytic converter, messed up O2 sensors, piston ring compromise, brown stains on the side of your car above the tailpipe.

Ah, yes.....the dreaded brown stains. I knew my advice to one of the lesser informed was correct. Thanx for checkin' my work there Crash.

 

[Vince]

Run engine with 87 octance it pings. Run it with 89 But as far as performance, no difference I can see.

 

[Chris0nllyn]

MOST vehicles can run 87 no problem.

Unless the owners manual call for 92/93 octane, you're just wasting your money.

 

[aps45819]

MOST vehicles can run 87 no problem.

Unless the owners manual call for 92/93 octane, you're just wasting your money.

It's the anti-knock rating of the fuel not an energy rating.

83 octane is easier to ignite than 91 octane fuel.

High compression engines need the higher octane to prevent the air/fuel charge from igniting prematurely. It won't hurt your engine to run high test but it won't do anything for you other than empty your wallet

 

[Chris0nllyn]

It's the anti-knock rating of the fuel not an energy rating.

83 octane is easier to ignite than 91 octane fuel.

High compression engines need the higher octane to prevent the air/fuel charge from igniting prematurely. It won't hurt your engine to run high test but it won't do anything for you other than empty your wallet

Yea, I think a lot of people think the higher the octane, the more power.

Fill up with 87, and be glad your car doesn't need 93 (like mine)

 

[glhs837]

Old Neon was able to run either 91/93 or, at the press of a button, 100 octane for a 50 wheel horsepower bump But normal Neons wouldnt need anything beyond 87. Wifes truck the kiddos 91 Geo, and my bike all swill the cheap stuff, but the Charger requires 91/93, since it's a high compression engine.

 

[Gilligan]

It's the anti-knock rating of the fuel not an energy rating.

83 octane is easier to ignite than 91 octane fuel.

High compression engines need the higher octane to prevent the air/fuel charge from igniting prematurely. It won't hurt your engine to run high test but it won't do anything for you other than empty your wallet

Exactly.

Conversely, if higher octane rated fuel is recommended/specified for your (modern ECM controlled) engine, running lower octane fuel might not save you any money; the timing will automatically be retarded to avoid detonation and lower engine performance the result.

 

[czygvtwkr]

Too much octane means all the fuel won't burn so you'll have unburned fuel going out the tailpipe and blown by the piston rings. Issues? Messed up catalytic converter, messed up O2 sensors, piston ring compromise, brown stains on the side of your car above the tailpipe.

That is a load of crap

 

[GWguy]

My 2000 4.8L GMC is starting to ping and detonate with 87 octane. Also stumbling a bit, especially with the a/c on. I've been wanting to change out the O2 sensors, haven't gotten there yet.

I've been running a can of SeaFoam every other tankful with no real change, so pretty sure it's not injectors. Good thing... $100 bucks a pop x 8. Although the SeaFoam does make the engine run quieter and smoother.

And I have a noisy lifter which only makes noise 30 seconds after starting for about 20 seconds, then shuts up. 4 oz of Marvel Mystery Oil in the gas on fillup shuts that up too!

 

[DEEKAYPEE8569]

MOST vehicles can run 87 no problem.

Unless the owners manual call for 92/93 octane, you're just wasting your money.

Years ago, I had an '81 G.P.. I went through a SUMMIT Racing catalog and got a cartful of aftermarket stuff for it; cam, lifters, aluminum intake, carb, hedders, dual exhaust; all that stuff disabled the stock computer.
I had to run 93 octane or better or that thing would run like it was trying to shake itself apart. On 93 though, that thing would run like a dog.

Kinda wish I still had it.

 

[glhs837]

That is a load of crap

Sort of, it's a matter of scale, I think. Going up 2-4 octane points, not so much as Z06 described. Those sorts of symptoms are much more likely were you to run a bunch of 100/105/110 octane race fuel.

 

[Chris0nllyn]

Years ago, I had an '81 G.P.. I went through a SUMMIT Racing catalog and got a cartful of aftermarket stuff for it; cam, lifters, aluminum intake, carb, hedders, dual exhaust; all that stuff disabled the stock computer.
I had to run 93 octane or better or that thing would run like it was trying to shake itself apart. On 93 though, that thing would run like a dog.

Kinda wish I still had it.

It gets really pricey when you have to run C16 Race Fuel (117 Octane)...$80 for 5 gallons

 

[glhs837]

One reason I rarely used the High Octane Mode button in the Neon, $5 a gallon was a chunk on change, even for a 12 gallon tank.

 

[DEEKAYPEE8569]

It gets really pricey when you have to run C16 Race Fuel (117 Octane)...$80 for 5 gallons

I don't have to. Dad does. He rebuilt his '68 Javelin; say what you will about them;for the drag strip, so it absolutely will not run on pump gas.
AV gas though.....she SCREAMS.

 

[glhs837]

My heart has always loved the Javelin. It has also loved wierd Saabs and some British cars. My head has always been able to wrestle my heart to the ground before spending money.

 

[Chris0nllyn]

I'm just a car guy in general I guess. I love em all, minus the imports that are slow as piss, with a loud muffler, and huge wing......and Fords

 

[DEEKAYPEE8569]

My heart has always loved the Javelin. It has also loved wierd Saabs and some British cars. My head has always been able to wrestle my heart to the ground before spending money.

You didn't go to L'town for the recent car show, did you? We were there.

 

[glhs837]

I'm just a car guy in general I guess. I love em all, minus the imports that are slow as piss, with a loud muffler, and huge wing......and Fords

You didn't go to L'town for the recent car show, did you? We were there.

Oh, I van find a good word to say about almost any car, but some, I can find more good words than others How about huge wing, load exhaust, and fast? Are you okay with that?

No, Dee, did not make it, been very hectic lately.