89 Octane gasoline

[ram57ta]

20 years ago when my 82 V6 Regal had over 100k miles on it the engine would rattle on anything less than 89 octane fuel (worn rings). When I bought my 83 Supra and started tinkering with timing at the track I didn't gain anything in ET or MPH from either 93 octane OR 100 octane (normally aspirated). When I picked up my 94 T/A I initially put premium in it (93) to check the mileage...then I switched to 87 and checked again......under all driving conditions I could not tell ANY difference....it ran the same. When I picked up my Grand National (turbo V6) I did the same experiment...started with 87...noticed some pinging on hard acceleration...it got slightly better with 89 octane....and essentially went away with 93 (using the stock boost and chip). My 98 GMC with 218k miles (vortec 350) has a slight bit of knock at WOT under a load on 87....with 93 octane its better...but I cant tell any difference between 87 and 89 other than the price.

[71chevellejohn]

Premium fuel is bullshit anyways.

Premium fuel isn't bullshit, there are specific applications where it is needed. The general misconception among the masses is since it costs more, it must be better for their vehicle than the less expensive fuel. And what you end up with is soccer moms unnecessarily filling the minivan with premium(or mid) thinking they are getting more out of it, when really they are just wasting money.

And jdgregory, the octane levels tend to vary by region, not state. Last time I went through El Paso there were pumps that were 86/88/90. And I remember seeing as low as 85 octane fuel in Colorado.

I have been told that a lot of it has to do with elevation, but I don't have the science on hand to back it up. I also don't have a logical explanation for mid grade.

I'm sure someone that knows more will be along to give you some type of answer.

[jdgregory84]

20 years ago when my 82 V6 Regal had over 100k miles on it the engine would rattle on anything less than 89 octane fuel (worn rings). When I bought my 83 Supra and started tinkering with timing at the track I didn't gain anything in ET or MPH from either 93 octane OR 100 octane (normally aspirated). When I picked up my 94 T/A I initially put premium in it (93) to check the mileage...then I switched to 87 and checked again......under all driving conditions I could not tell ANY difference....it ran the same. When I picked up my Grand National (turbo V6) I did the same experiment...started with 87...noticed some pinging on hard acceleration...it got slightly better with 89 octane....and essentially went away with 93 (using the stock boost and chip). My 98 GMC with 218k miles (vortec 350) has a slight bit of knock at WOT under a load on 87....with 93 octane its better...but I cant tell any difference between 87 and 89 other than the price.

So unless you own an '81 Buick Regal, 89 octane fuel is useless. I will have to let this satisfy my thirst for knowledge. Time to ummmm....party.

[jdgregory84]

Premium fuel isn't bullshit, there are specific applications where it is needed. The general misconception among the masses is since it costs more, it must be better for their vehicle than the less expensive fuel. And what you end up with is soccer moms unnecessarily filling the minivan with premium(or mid) thinking they are getting more out of it, when really they are just wasting money.

And jdgregory, the octane levels tend to vary by region, not state. Last time I went through El Paso there were pumps that were 86/88/90. And I remember seeing as low as 85 octane fuel in Colorado.

I have been told that a lot of it has to do with elevation, but I don't have the science on hand to back it up. I also don't have a logical explanation for mid grade.

I'm sure someone that knows more will be along to give you some type of answer.

Dude, I've researched it enough. I've heard that California does 91 because of emissions even though I heard the hotter fuel burns, the less emissions and the higher the octane, the higher temperature it burns at, creating a more powerful ignition hence the potential power increase. California is ran by some of the biggest retards though so to think that higher octane means higher pollution would be right on par with them.

[petyweestraw]

Most guess now say to use 87. So why not. Just don't use cheap stuff

Angry Panda Poon Rawrrrrrr!!!

[jdgregory84]

Most guess now say to use 87. So why not. Just don't use cheap stuff

Angry Panda Poon Rawrrrrrr!!!

Fortunately, I've never had a fuel issue with my vehicle, but I have been a service writer and have seen a few issues with fuel being the problem. I've seen wal-mart as a problem a couple of times, but I've also seen shell, and chevron which are typically higher in cost for the same grade. A bad batch is a bad batch no matter where it comes from.

[ram57ta]

Premium fuel isn't bullshit, there are specific applications where it is needed. The general misconception among the masses is since it costs more, it must be better for their vehicle than the less expensive fuel. And what you end up with is soccer moms unnecessarily filling the minivan with premium(or mid) thinking they are getting more out of it, when really they are just wasting money.

And jdgregory, the octane levels tend to vary by region, not state. Last time I went through El Paso there were pumps that were 86/88/90. And I remember seeing as low as 85 octane fuel in Colorado.

I have been told that a lot of it has to do with elevation, but I don't have the science on hand to back it up. I also don't have a logical explanation for mid grade.

I'm sure someone that knows more will be along to give you some type of answer.

I think generally....any somewhat modern EFI vehicle thats NOT forced induction should run just fine with 85-87 octane fuel. ANY forced induction (turbo, supercharger) or modified high compression OR high timing engine should run premium fuel to prevent pre-ignition or detonation. High mileage (worn rings/lower compression) might benefit from higher octane to prevent ignition rattle. Not sure there is a specific answer for EVERY car...just gotta test it and see what works best for your driving needs.

[majorownage]

Dude, I've researched it enough. I've heard that California does 91 because of emissions even though I heard the hotter fuel burns, the less emissions and the higher the octane, the higher temperature it burns at, creating a more powerful ignition hence the potential power increase. California is ran by some of the biggest retards though so to think that higher octane means higher pollution would be right on par with them.

It doesn't burn hotter... The flame front moves slower, and is less resistant to going supersonic and forming a shockwave, which causes a ping.

[JC316]

I think generally....any somewhat modern EFI vehicle thats NOT forced induction should run just fine with 85-87 octane fuel. ANY forced induction (turbo, supercharger) or modified high compression OR high timing engine should run premium fuel to prevent pre-ignition or detonation. High mileage (worn rings/lower compression) might benefit from higher octane to prevent ignition rattle. Not sure there is a specific answer for EVERY car...just gotta test it and see what works best for your driving needs.

My 4.3L blazer HATED 85 octane, it would barely run on the stuff. My 93 300zx and my friends 93 Infinity J30 didn't do well on 87, had some pinging. My t-bird SC would ping like all hell on 87.

[exlude]

If you're pinging on 87 it doesn't hurt to try 89 to get rid of it...

[ram57ta]

My 4.3L blazer HATED 85 octane, it would barely run on the stuff. My 93 300zx and my friends 93 Infinity J30 didn't do well on 87, had some pinging. My t-bird SC would ping like all hell on 87.

Every car is different and there are a lot of different factors that come into play obviously. Ambient temp, humidity, condition of engine, mileage, state of tune, etc.... I have switched back and forth from 87 to 93 on occasion in my 99 Honda CBR1100xx just to see if I could tell any difference...and even in 100+ temps...nope...not a damn bit of difference. If I did that in my Grand National in 100+ days...I'd have blown head gaskets.

[petyweestraw]

My 4.3L blazer HATED 85 octane, it would barely run on the stuff. My 93 300zx and my friends 93 Infinity J30 didn't do well on 87, had some pinging. My t-bird SC would ping like all hell on 87.

Older cars especially carb cars was bad about it the older they got. The carbon build up would get hot and cause predetination that caused the pinging and ruff running

Angry Panda Poon Rawrrrrrr!!!

[JC316]

Every car is different and there are a lot of different factors that come into play obviously. Ambient temp, humidity, condition of engine, mileage, state of tune, etc.... I have switched back and forth from 87 to 93 on occasion in my 99 Honda CBR1100xx just to see if I could tell any difference...and even in 100+ temps...nope...not a damn bit of difference. If I did that in my Grand National in 100+ days...I'd have blown head gaskets.

Definitely. My Northstar Cadillacs all claimed to need premium and I never had an issue with 87. The SC was running nearly 15 PSI, so good reason that 87 pissed it off.

Older cars especially carb cars was bad about it the older they got. The carbon build up would get hot and cause predetination that caused the pinging and ruff running

Angry Panda Poon Rawrrrrrr!!!

My 351c pings some under hard acceleration, damned carb.

[jdgregory84]

It doesn't burn hotter... The flame front moves slower, and is less resistant to going supersonic and forming a shockwave, which causes a ping.

Really good to know. Thanks.

[jdgregory84]

My 4.3L blazer HATED 85 octane, it would barely run on the stuff. My 93 300zx and my friends 93 Infinity J30 didn't do well on 87, had some pinging. My t-bird SC would ping like all hell on 87.

Where the hell do you get 85 octane? Never seen it.