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Hey guys,

I have a 2000 323 ci automatic and was wondering if I should be using the premium gas or if the regular is fine? Thanks!
 

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YEEEES!

please please premium only. it is smart and it has knco sensors, but it can only retard ingition so much before it starts detonating.

peter
 

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Premium gas is the best for all cars. Yes, we know that.
But... your questoin was if Regular would be fine... and, yes
it would also work. Even though you have a bimmer, that
doesn't necessarily mean you need to use premium. It just
means it runs better and lasts alittle longer. All cars were made
to beable to run on regular, because not everybody could afford
or find regular gas wherever they are. BMW's, jags, merc's,
highend cars like that are made so they can go places and
do things other cars can't, and so they can run completly on
regular gas. Peace :rock
 

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NOOOO!

these engines compress at more that 10:1. indeed they do have knock sensors usually for each cylinder but there are limits on the ignition retardation pre-programmed in the computer injection/ignition map. these programs are based on minimum octane requirements (usually 91 for the u.s. cars) so if you start putting 87 it WILL detonate.

normal flame advance speed is about 40 to 80 m/s (or some goddamn metric unit i cannot remember anymore). low octane can cause inaudible detonation which is usually at about 1000 m/s. this overheats anything that sticks into the combustion chamber, such as plug ceramic or electrodes. plugs can crack and chip, heads warp, all kinds of very bad things happen. also, it will drive like a dog, cos it will not advance timing.

please don't do this to your car...

manufacturers will specify if you can use regular, this is not a conspiracy to get 10c more per gallon out of your pocket.

premium gas is of no advantage for cars that do not need it. as far as i know the detergents are the same regardless of octane rating (prevents valve and more importantly injector nozzle deposits).

in countries where hi octane is not available (these days this is really nowhere, cos third world uses tetraethyl lead) the maps are different or more historically compression ratios are different (by using different pistons, e.g. mercedes still did that in the 80s for the m180 motors).

peter
 

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Anybody know if there's any benefit to using 100 octane gas? It's available from Shell here in Germany. I have a 2003 325xiT (U.S. spec).
 

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from my one experience with 100 octane gas:

i had to drive from Maryland to Ohio and back during summer. I had a full tank of 93 octane gas when i left Maryland. I was just about empty when I arrived at Ohio (about 380 miles). Filled her up with 93 in Ohio, spent a few days there. When it was time to return home, I had about half tank of 93 octane left. I filled the rest of the tank with 100 octane. Drove back to Maryland (remember it was 380 miles). I had half a tank left when I got home! So basically, I drove 380 miles in half a tank where as with normal premium a full tank.
 

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I did get better gas mileage the one time I tried it. That's good, too, because I've only been getting about 17 mpg city. I hope that goes up once the car has more miles on it (I have about 4500 now).

100 octane gas is about $6 per gallon here, given higher prices and the awful exchange rate.... Yikes!
 

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Excuse me for being stupid, but the top two gas grades at the local Mobil are 91 and 93 right? Should the BMW be getting 91 or 93 or just 93?

Also, when I buy the car I'm going to obviousl yask the past owner what gas he had been using. If he hasn't been using the proper fuel should I keep using the 87 or should I switch over to the better stuff anyway?

I'm not particularly concerned with the performance aspect, just with whether or not it will reduce reliability significantly.
 

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in my part of the country (md) grades are 87, 89, 93.

i believe that manual states minimum of 91.

regardless of previous owner, use what is recommended. if the owner used regular, i'd consider leak down test to check the head. whetehr there is damage really depends how the car was driven (if it ever been overheated etc...)

peter
 

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I always go for as high octane as is available because the engine runs smoother, you feel greater power output and the engine doesn't struggle as much as well as all of the other obvious reasons already stated,,,, in the US, particularly in Southern Cal where I live, there's only 91 available, in Bangkok, where I live/work and bought my BMW 323i, the manual stated no less then 95 octane. Thailand used to have fuel no lower than 93 and as high as 97 for pretty much the same prices they have in LA, now they don't have anything higher than 95 so I guess I'm a little lucky, the lowest is now 92 here but it depends on the gas station
 

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for me no less than 91 but i try to get 94 as much as possible. my performance chip permits me to have any less than 91
 

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octane numbers between different countries are not necessarily comparable.

e.g in the e.u. bmw run on 98 octane. i beileve that this is comparable, and higher than the gas in the u.s. bmw knows this, and adjusts the ingition map to compensate.

no idea about thailand, but it is likely they have a legitimately higher octane.

regarding very high octane gas: usually there is no difference in performance, nor gas mileage. it used to be true about high octane due to high content of aromatics: they have both higher energy density and higher octane then regular aliphatic hydrocarbons. this is no loger utilized in the u.s. due to emissions problems.

it certainly will not hurt the car, unlike low octane.

peter
 

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Originally posted by peterkulesza@Dec 29 2003, 12:26 PM
oh, and of course with chiped cars all bets are off, use the highest you can get as someone stated.

peter
well its sort of true, but usually anything over 91 octane should be fine. dont even think of 87 octane
 

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Originally posted by BIg Pappa@Jan 1 2004, 09:35 PM
RTM. no offense but this thread is a no-braniner
MK
yeah and if you read the manual it says it recommends using 91 or above but the car will be fine "as long as the minimum requirements of 87 octane are met"
 
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