FenixSS

iTrader: (3)

I just got a V6 firebird and recently learned from the previous owner that he's been putting 92 for the past year in it.

I remember reading that putting a higher octane than required is not a 'treat' for the engine, but what are the other possible consequences especially since I'll be switching back to 87.

LS6427

iTrader: (2)

What a dumbass he was. If the engine is fine and runs great its probably ok. He just wasted alot of money for a year.

Nothing will happen if you go back to 87....but please do, a V6 gets absolutely nothing out of a higher octane.

Higher octane is for higher compression engines.


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junkindatrunkmx6

iTrader: (1)

The octane is the gases ability to resist detonation... Your engine should not have detonation issues...

jcws6

iTrader: (1)

What these guys said is right. Put whatever gas your manual recommends in the car. Using anything higher is just a waste of money.

FenixSS

iTrader: (3)

Thanks for clearing that up guys. Peace.

Dewey

iTrader: (1)

sorry to disagree here, but if you switch back you screw yourself. Talking from personal experience, it's just like going from sythetic to conventional. if the engine is used to high octane fuel, then the engine will run like crap with the lower octane.

2002_Z28_Six_Speed

iTrader: (19)

Putting a higher octane gas in your vehicle will cause less than optimal combustion. As it will burn more slowly so there is no reason to do so unless combustion is too quick and thus reducing your power.

91RS383

If you're engine does not run well after the switch back to 87 you probably have side effects from poor combustion, and should do a top engine clean. Use MCCC or similar. The copression ratio of the engine determins the octane requirements.

fleetmgr

Have to disagree. If you managed to see a measurable difference, then you had other issues to begin with. Octane only effects the ability of a fuel to resist detonation. Anything else is imaginary.

There are no effects (short term) in switching between regular and synthetic oils.

LS6427

iTrader: (2)

sorry man Its not a child we're talking about that is used to playing with Johnny every Friday after school, and now he can't anymore, he's gonna cry. Its a bunch of metal that does not change. The mechanics and specs have not changed. The compression is the same...UNLESS there's damage to something. But if there's damage to say a ring or piston, the compression will go down and gas isn't much of a factor, it needs to be fixed.

Now possibly there's a mechanical issue we don't know about, but nothing at all will happen by going back and forth every day with different octanes. If a high compression guy uses lower octane, well he's gonna damage things through detonation.

My stepfathers Dodge Hemi truck, in the manual, it says you can go back and forth from 87 to 89 all you want if one is not available.


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fleetmgr

In todays cars, it should never happen. Thanks to the knock sensor, the ECU should automatically pull timing out to compensate.

LS6427

iTrader: (2)

True, but it still happens. We continually have people coming here asking what the "metal marbles" sound is under the hood when they're accelerating.

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fleetmgr

Wow...I can't remember the last time heard a car ping. Now, my lawnmower does occasionally. Remember the late 70's/early 80's knock-o-matics?

LS6427

iTrader: (2)

Pre-knock sensor era.

There was a guy here last month who had some bad detonation. Turned out to be burnt oil build-up on his pistons from bad valve seals. Same exact thing that happened to my friends 427ci, we took his heads off for a rebuild and cleaned the pistons off in the driveway. The detonation was unbelievable, raced a Mustang and the guy in the Mustang heard it during the race. It was horrible. I don't know how the engine survived this, he drove around for weeks like that and didn't know what it was.

The burnt oil was getting hot spots after the engine was hot and they were igniting the fuel/air right before the spark plug did, and while the piston was still coming upward towards TDC. Some of the valve reliefs were completely filled in.




Cleaned up: Took like 4 hours to clean all 8 pistons.




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fleetmgr

It's truly amazing how far we've come. I remember when that sort of carbon build up would have been considered normal, not in the last couple decades, though.

When I first started wrenching, it wasn't unusual to spend 5-10 minutes on each valve getting the deposits off of them prior to grinding. I'd have to spend a couple hours on each head with a wire wheel in the valve pockets. Lots of lead/ash buildup...great stuff to breathe.

thatguy383

iTrader: (1)

All gas is the "same"- (don't take that the wrong way) higher the the octane the more resistant it is to premature detonation due to higher compression... as far as synthetic to conventional, that's like saying you can't switch back to water from gatorade...

if it doesn't need premium don't run it, if you have money run synthetic oil...it's better..but in this day and age conventional oil is good too... synthetics just have more detergents and old people are scared of **** breaking loose and "bad ****" happening... i doubt it..

LS6427

iTrader: (2)

Well, to me....the whole idea/design of a PCV system is just crazy. Oil going into the "air" intake and flowing across very very hot metal surfaces. Thats just ridiculous. Its gonna stick, period.

I know alot will say I'm nuts, but I'm testing something to see what happens on my 427ci. Been 4 weeks now and I just did an oil change after 4 weeks. The old oil was completely normal as always when I change it with not one drop of moisture in it.

I completely capped off both intake ports, passenger and drivers side valve cover ports and I have absolutely NO MORE oil going into my intake. I put a breather filter on my valley cover crank case exit port. I'm going to add a breather/filter to my oil fill cap.

I have no more oil burn either. I was burning 1 qrt every 2 weeks, now my oil consumption has completely stopped. My 02 sensors are gonna love that and my fuel/air is now proper. My engine is noticably, running better and smoother. I also would get black soot build-up on my rear bumper above both tailpipes after about 1 week of driving...because I figure that the oil going through my engine is making the PCM add fuel, so I'm always rich. 4 weeks later, my bumper is still as clean as it was 4 weeks ago when I cleaned it all off when I started this experiment.

I'm checking the oil daily for any strange changes or moisture....so far everything is perfect.

91RS383

HAZ-Matt

iTrader: (8)

I had a 2000 3.8L Firebird. At any rate the 3800 SII timing tables are setup for 87 octane and you will basically be in the high octane table all the time on 87 which means you will gain no power at all running anything higher.

If you had HPTuners you could change your spark tables and tune it for 91+ and pick up about 5-10HP in the midrange. That would be the only reason you might want to run anything better than 87 on that motor.

NHRAMAN

iTrader: (1)

Your V6 will be fine on 87 Octane...Period. ......