87 Octane

[M340i Pride]

Originally Posted by Seattle S65B40

Whether it's noticeable or not, I would never put less than 91 octane or gas from any station other than Shell or Chevron. That dude sounds like a cheap bastard and his M3 should be revoked.

revoked lol

[Erie Von Otto]

Thing is that with lower octane fuel it will not burn as efficiently. So while you maybe saving $2-5/fill up, you have to fill up more often costing you more in the long run. It is simple, period. Plus, you can so tell the difference when going from 87 to 91+. My first car during high school (1990) would get the 91 octane ($1.20/gal) treatment on payday and she was happy for a full tank. Then it was back to 87 ($.95/gal)...

[smmmurf]

Was this an E9x M3? ... what an idiot

I could immediately tell the difference between 87 and 91 in a 328i rental car... it came with 87. After 1 tank of 91 it was much faster. When I put 87 back in it to return it as recommended by the agency, the car was noticeably slower.

[Joey]

OK DONT Flame me for this one, but it will be helpful....dont yell at the 91 Oct guys, in some states, that is the best you could get. I think the ONLY thing I liked about living in Philly is that the Sunoco had Ultra 94, I would always put that in my E36 when I lived up there 10 years ago.

In FL, we can get 93, I will only use Shell or Chevron so I think they are the best.

As for the flame....I accidently had 87 in my M3 once. In fact, it was last week. I just made an honest mistake, and hit the pump all the way to the left, rather than all the way to the right and filled her up with 87, the tank was bone dry and didnt even realize it till I actually drove the car and was getting some hesitation.

I thought I was nuts, but it kept happening when I went to floor it.

Still scratching my head, I was about to schedule a trip to the dealer. Fortunately for me, I have to save my gas reciepts and there you have it, I filled it with 87 2 days prior.

I drove it out on the highway (and got a little LESS MPG than normal, and I wasnt romping it) filled it up with 93 and the car was fine.

[Asiarush]

Originally Posted by BobsM3Coupe

I believe leaded gas for on road vehicles was banned in the US in the mid 90's.

yes you guys are right....sorry my comment was wrong.
learned something today about gas octane.

thanks

[ES_TRADER]

Originally Posted by Joey

As for the flame....I accidently had 87 in my M3 once. In fact, it was last week. I just made an honest mistake, and hit the pump all the way to the left, rather than all the way to the right and filled her up with 87, the tank was bone dry and didnt even realize it till I actually drove the car and was getting some hesitation.

this reminds me, i have friend who did the exact same thing as u a while back..she was in a hurry and didnt look at the pump and quickly grabbed the nozzle...unfortunately for her, it wasnt 87 octane....it was Diesel #2, filled a full tank, right into the petrol engine...tow truck...she never made it to her appt..

[MienAce]

Originally Posted by klammer

Use 93 all the time, as an aside, if I use 100, will I notice a difference up top? Also have 110 to choose from (both at the track, not around the corner), will that make a difference? Or is it just overkill and unusable at that point? Insights would be appreciated

if youre not tune for 100 or 110 oct, not worth it u wont feel much.

side note: Ive got 49 AWHP from 91 to e85+tuned.

[1MOREMOD]

Originally Posted by richpuer

this reminds me, i have friend who did the exact same thing as u a while back..she was in a hurry and didnt look at the pump and quickly grabbed the nozzle...unfortunately for her, it wasnt 87 octane....it was Diesel #2, filled a full tank, right into the petrol engine...tow truck...she never made it to her appt..

how do you do that the nozzle doesnt fit and is always a different color also.

[ES_TRADER]

Originally Posted by chriszeh

how do you do that the nozzle doesnt fit and is always a different color also.

i have no idea...i asked the same question...it was on a prelude...all i know is i was called to give a ride and saw the car on a tow truck...some pple are just clueless

[1MORELAP]

Originally Posted by Edjay

Food for thought.
You may not do damage by using lower octane fuel. But most likelly you will spend more in the end. With lower octane, the engine is more likely to pre detonate. The knock sensor will pick that up and compensate for it. It does this in 2 ways. 1 would be to retard ignition timing, the other would be to richen the fuel mixture some. It does this in trying to lower combustion temp down. So imo the end by produuct if this would be less engine power but more fuel used. With less engine power, equals less mpg equals more money spent.

Correct. Except not proven if the increase in fuel consumption that is very likely will be larger or smaller than the difference in fuel price.

[1MORELAP]

Originally Posted by Joey

As for the flame....I accidently had 87 in my M3 once. In fact, it was last week. I just made an honest mistake, and hit the pump all the way to the left, rather than all the way to the right and filled her up with 87, the tank was bone dry and didnt even realize it till I actually drove the car and was getting some hesitation.

I thought I was nuts, but it kept happening when I went to floor it.

Still scratching my head, I was about to schedule a trip to the dealer. Fortunately for me, I have to save my gas reciepts and there you have it, I filled it with 87 2 days prior.

I drove it out on the highway (and got a little LESS MPG than normal, and I wasnt romping it) filled it up with 93 and the car was fine.

87 and HOT weather (FL) will do exactly this - retard timing to degree that you will notice. Good post.

[1MOREMOD]

Originally Posted by richpuer

i have no idea...i asked the same question...it was on a prelude...all i know is i was called to give a ride and saw the car on a tow truck...some pple are just clueless

oh it was a girl that makes sense now.

[1MORELAP]

OK, let me summarize. I am not a tuning expert, or actually not an expert in anything. But I have played with tuning turbo cars before.

1. Running 87 Octane in a car designed for 91+ will in most instances HURT the engine. Although the ECU will compensate, it will compensate only AFTER detecting knock. And since its designed for 91 Octane the ECU will keep reverting to the high octane map and continue knocking - testing the gas - and pulling back timing and adding fuel. That is not good for the engine.

2. Ethanol in fuel is not bad, although it contains less energy - therefore increases fuel consumption it has a very high octane rating. Small engine, turbos, ethanol - HUGE power. If you can get 100% gas and then add 10% Ethanol you would increase Octane rating substantially. Since un-tuned M3 will adjust to 93/94 octane, this could be a neat trick for the Cali 91 Octane souls. Read here more if you like - http://en.wikipedia.org/wiki/Ethanol_fuel

3. If you run 87 Octane, you are very unlikely to feel any difference with the engine screaming at 8,000 RPM. Actually, 6,000 and above you will feel none. Dyno may, but you will be unlikely to. You will feel the difference - hesitation when you floor the car at 3,000 RPM without downshifting. At 3,000 RPM I would not call it lugging, but it is at the lower RPM range and right when you go to WOT that the car will knock and the ECU will struggle to compensate. Do that at 1,500 RPM and you will feel and hear the difference. Your engine is aging/dying quickly here.

4. ECU compensates for lower octane by reducing timing and adding in more fuel, the driver likely compensates for pulled timing (less power) by pressing the accelerator a bit deeper which results in more air and fuel. (I was going to experiment on wive's Land Rover to see if the drop in mileage on 87 erased ALL or just a portion of the savings associated with pumping 87.)

5. AIT - Air Intake Temperature has also a large impact on knocking - hot air + more tendency to knock. Not that I would recommend, but I would venture to say that in freezing weather our cars would run healthy on 89 octane. While in hot - Arizona summer type of weather 91 is possibly not enough. Though don't fret too much, unlike octane that the ECU can not measure directly, it does measure AIT, so it will select the appropriate - less aggressive map. So it will not need to compensate for lower octane gas - it will not ping to start.

6. It is unlikely that a stock M3 would benefit from anything above 94 Octane in normal weather. Tune or better forced induction would be needed to do that. When tracking the car in very hot weather - thinking Texas or Las Vegas, due to elevated AITs going to a mix of 96, 98 octane could and probably will be felt even on a stock tune. (I wonder if sticking ice cubes into the intake would do much... I bet it would for 1/4 mile runs!)

The bottom line: Stick with 91+ octane top tier gas for your M3, as you are unlikely to save any money going to lower octane and possibly will pay later.

[carlfan]

Since you're commenting about some random person that you noticed in a gas station, should I remind people here, that not everyone that drives an M3 (or any performance car), are car fanatics. Some people are just cheap or simply don't give a damn about their cars!

I know a guy that make millions a year, yet refuses to pay an $80/month private garage parking at his workplace. This person was happy parking his new Porsche 911 Turbo on the street for $0, and walking 4 blocks. This same person also criticized me one day for popping my M3's hood and showing the engine to a coworker. He just couldn't understand why I cared so much for a stupid car.

[kwike92]

Originally Posted by Seattle S65B40

Whether it's noticeable or not, I would never put less than 91 octane or gas from any station other than Shell or Chevron. That dude sounds like a cheap bastard and his M3 should be revoked.

Bahahahahah +1

[NAV8TT]

May be he didn't notice any change in performance but he is hurting this engine pretty bad and he will soon notice many changes not only in performance. Low octane leads to knocking and early combustion in the chambers that hurts the engine and shortens its life span.

[j2m]

Originally Posted by carlfan

Since you're commenting about some random person that you noticed in a gas station, should I remind people here, that not everyone that drives an M3 (or any performance car), are car fanatics. Some people are just cheap or simply don't give a damn about their cars!

I know a guy that make millions a year, yet refuses to pay an $80/month private garage parking at his workplace. This person was happy parking his new Porsche 911 Turbo on the street for $0, and walking 4 blocks. This same person also criticized me one day for popping my M3's hood and showing the engine to a coworker. He just couldn't understand why I cared so much for a stupid car.

Well... OP's had about A YEAR AND A HALF to get over it but thanks for the reminder

[1MtoM3]

Originally Posted by 1MOREMOD

Is a tuned car less able to deal with lower octane gas or does it still retard the timing in a similar way so no damage occurs. Conversely would using a higher octane than you are tuned for be a waste or can the tuned ecu manage to adapt and make more power?

My Ess tune for the 1M would adjust for higher than tuned octane, don't know for lower though.
My Cobb tune for my old STI wanted just the gas it was tuned for I think.
But I used to put 91 instead of 94 all the time in it and never noticed pinging or whatever else.

[nybimmerfan]

Originally Posted by PINHEAD

I put jet fuel in my car

Jet fuel in reality is unleaded kerosene or naphta-kerosene blend.

[Brucewonder]

maybe the m3 is his lease beater and has a f430 for the weekends.

[njdrive]

As I’m looking to buy an M3, it is past owners like this who concern me. If the car calls for 91 plus octane, put the required fuel in the car. I know I had to put 87 octane in my 330i and I felt the difference immediately. If he said he didn’t notice the difference then he obviously doesn’t drive this car to its fullest potential. I wonder if he skimps on repairs and tires too.

[njdrive]

As I’m looking to buy an M3, it is past owners like this who concern me. If the car calls for 91 plus octane, put the required fuel in the car. I know I had to put 87 octane in my 330i and I felt the difference immediately. If he said he didn’t notice the difference then he obviously doesn’t drive this car to its fullest potential. I wonder if he skimps on repairs and tires too.