I've just purchased my first bimmer, an '87 325ic. The owner's manual specifies 91 RON, which is the European standard of measuing. I've found information on the internet that 91 RON equals 87 R+M/2, also known as the Anti-Knock Index (AKI), which is the standard of octane measurement in the US. That suggests I can safely run unleaded regular 87. The only information I can find about octane requirements is related to pinging: if it pings under acceleration or load, you need to run a higher octane. I've only run 3 tanks of gas through mine, all regular 87 , and get no pinging. Is there another reason I should be running a higher octane, perhaps 89 or 91, or is it okay to run 87?
What grade and octane should I be burning?
- Thread starter greybeard
- Start date
Never user higher than required
the alcohol used to provide the higher octane is not as efficent.
The MTBE used for 20 years in the US is being outlawed.
http://www.mtbecontamination.com/
You will get less power from the higher octane fuels, even MTBE.
Only use higher octane if the engine is pinging or if you have a huffer or puffer.
Later,
the alcohol used to provide the higher octane is not as efficent.
The MTBE used for 20 years in the US is being outlawed.
http://www.mtbecontamination.com/
You will get less power from the higher octane fuels, even MTBE.
Only use higher octane if the engine is pinging or if you have a huffer or puffer.
Later,
Any idea why? Everything I read about gas grades and octane says that higher octane doesn't give better gas mileage, doesn't increase power, doesn't make the engine run smooter, etc.... that it's all and only about pinging..... A friend of mine who has one said bimmers need higher octane because they are "high-compression engines," yet when I asked him what that meant and why a "high-compression engine" needed higher octane, he didn't know. I'm not saying he's wrong, but I'd sure like to know why I should run higher octane if I'm not getting any pinging. Ive also heard explanations that higher octane grades have better additives and will keep the injectors cleaner, but nothing I can find in any articles suggest that. Any ideas?
My M50 engine in my 525i specifies that premium gas should be used, i never ever use it, and it never knocks... I would just use the cheap stuff until the car starts knocking... I believe that the m20 doesn't require high octane fuel... Higher octane fuel will do you no good unless your engine requires it... some BMW engines are high compression and some are not... When engines have higher compression, the fuel combusts differently, and then a higher grade octane fuel should be used, or else the engine will ping or knock, and that can cause engine damage....
if i had the time & energy to type out a long response teaching you all about compression, detonation & octaine rating i would.... but i don't... sorry ![[hihi]](/images/smilies/icon_smile_hihi.gif "Hi Hi [hihi]")
but i'll tell you this...
the m20b25 (engine from a an e30 325i) has a compression ration of 8.8:1... that's actually pretty LOW... so what your buddy told you is wrong. and BMW designed (most) of their engines to run just fine & efficient w/ basic 87 octaine gasoline... so again, what your buddy told you is wrong.
here's a link that'll explaine more about octane, compression etc
http://auto.howstuffworks.com/question90.htm
by the way... i run premium (92+) in my car for the sole reason that i have a chipped ecu, which requires it (even though i installed it w/ a full tank of 87 & ran it like that for a week w/ no problems, i just didn't get on the gas as much as i normally do)
but i'll tell you this...the m20b25 (engine from a an e30 325i) has a compression ration of 8.8:1... that's actually pretty LOW... so what your buddy told you is wrong. and BMW designed (most) of their engines to run just fine & efficient w/ basic 87 octaine gasoline... so again, what your buddy told you is wrong.
here's a link that'll explaine more about octane, compression etc
http://auto.howstuffworks.com/question90.htm
by the way... i run premium (92+) in my car for the sole reason that i have a chipped ecu, which requires it (even though i installed it w/ a full tank of 87 & ran it like that for a week w/ no problems, i just didn't get on the gas as much as i normally do)
Before I put a Conforti chip in my 89 I ran 87 octane with NO problems. With a chip installed you must use a minimum of 91 for 2 reasons 1- prevent detonation (pinging) and 2- In order for the chip to work it has to advance the timing. The only time you would need higher octane in a stock engine is if the engine is very carboned up and/or you experience very hot (desert) outside temperatures on a regular basis since the octane requirements of an engine increases with temperature. The M20 engine does not have knock sensors and did not need them.
your car never knocks and will never knock no matter what octane you use. it's because modern cars have a knock sensor which retards engine perf, so you won't burn up low octane gas due to high engine temp. knocking sound iirc was prevalent in the 60s cars, and gas prematurely burning up made the engine make the knockign sound..
altho how much perf you lose by using lower octane gas is up to debate, and i for one don't have a clue, but i've been and will always be using the 93% octane. i dropped enough for a nice car w/ high perf engine, i'm not about to go cheap and not get my money's worth.
when i had a blazer, which needed only regular, i did get lil more milage w/ the premium, but way i see it, the lil advantage is a wash, since i pay a lil more per fill up, and i get to goto the gas station a lil bit less.. (DEF not scientific!!![[:D]](/images/smilies/biggrin.png "Big Grin [:D]")
but works for me.
altho how much perf you lose by using lower octane gas is up to debate, and i for one don't have a clue, but i've been and will always be using the 93% octane. i dropped enough for a nice car w/ high perf engine, i'm not about to go cheap and not get my money's worth.
when i had a blazer, which needed only regular, i did get lil more milage w/ the premium, but way i see it, the lil advantage is a wash, since i pay a lil more per fill up, and i get to goto the gas station a lil bit less.. (DEF not scientific!!
but works for me.
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