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E34 (1989 - 1995)

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  #1  
Old 02-19-2013, 06:39 PM
Larrick Larrick is offline
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High octane vs. low octane

I'm sure that this question has been asked before. Does the added cost of high octane get you better gas milage; enough to off set the cost?
I understand that high octane gas usually has cleaning additives that may also help prevent problems and save more money.
In California most gas stations have 87, 89, and 91 octane.
Is one gas brand better than another?
Gas with Techron for instance?
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  #2  
Old 02-19-2013, 06:44 PM
TopByron TopByron is offline
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I have seen cars that would about cut off when you put lower octane gas in them. BMW recommends at least 91 Octane whether you decide to buy cheaper lower octane and add a $6 bottle of booster or pay the extra 30 cents a gallon for 18 gallons. In my experience Techron, Shell and BP fuels all run better than generic, but many will say they are all the same and paying more for name.
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  #3  
Old 02-20-2013, 06:41 AM
snowsled7 snowsled7 is offline
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Your car was optimised by BMW to run on 91 octane fuel. That is what you should run it on. It will run on lower octane fuel because it has the ability to retard the timing if it senses pre-ignition. This also reduces power, you you need a larger throttle opening to maintain the same power output eating up the less expensive fuel more quickly.

Best to just run what is reccomended.

Now my car came with an 87 octane requirement. At altitude our "regular" gas is 85 octane, and my car ran perfectly on it. When I added the chip tune, advancing the ignition timing, now I am required to run 91, which I do. My engine does not have those knock sensors and will hurt itself if I do not run the higher octane.

Running higher octane than required has no advantage. My car without the chip would not benefit in any way from running premium. The expert opinion I accept is that different brands run different additive packages. They are all more than sufficient to keep our old school systems working well. The main point was that each additive package will eventually leave some deposits. Switching brands every 3-4 months keeps build ups to a minimum and the new package cleans the old. So pick 2-3 good brands and rotate.

Consider that I am too lazy to take my own advice, buy fuel where it is cheap, or when I must. I have never had much problem with fuel systems that are maintained. Regular fuel filters, and a fuel injector service, which will pay for itself.
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  #4  
Old 02-20-2013, 12:39 PM
paperplane94 paperplane94 is offline
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Stock M20's and M30's are programmed to run on 87, for future reference.
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  #5  
Old 02-20-2013, 12:43 PM
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Monsignor Monsignor is offline
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Quote:
Originally Posted by paperplane94 View Post
Stock M20's and M30's are programmed to run on 87, for future reference.
+1

M20 Eta E28 Regular
M50 Vanos E34 Premium
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  #6  
Old 02-20-2013, 01:24 PM
Larrick Larrick is offline
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Premium, meaning 91 octane?
Should there be an increase in gas milage?
The knock sensors are there to retard the timing for the use of lower octane..True?
Is there any damage being done to an M50 vanos by running 87 octane aside from less power?
I do not necessarily want my son to drive any faster than he already does!
What type of gas milage should I be getting on a 1994 525i touring in mostly city driving?
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  #7  
Old 02-20-2013, 01:40 PM
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Monsignor Monsignor is offline
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sorry i should have specified. in the dirty Jersey Regular means 89 and Premium means 93

Then again, i'm tuned for 93 a la TMS chip
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  #8  
Old 02-20-2013, 04:35 PM
Microtesties Microtesties is offline
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My M20 likes 93 octane, so that's what I use. Probably still a bit more expensive than regular, but it's better for the engine so it's worth it.
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  #9  
Old 02-20-2013, 07:27 PM
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supertech777 supertech777 is offline
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My 95 525 with chip runs good on 91 but loves 93 , performance wise

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  #10  
Old 02-20-2013, 07:39 PM
snowsled7 snowsled7 is offline
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Quote:
Originally Posted by Microtesties View Post
My M20 likes 93 octane, so that's what I use. Probably still a bit more expensive than regular, but it's better for the engine so it's worth it.

That last bit is nothing more than an old wives tale. 93 octane fuel is in no way "better" for the engine. ALL modern fuels have heavy doses of additives. You do not need to buy premium to get them. Your engine management system is not designed to take advantage of the fuels properties and, the fuel alone does not offer a performance advantage.

Now with a chip tune, you can inexpensively add power and economy through improved efficiency, when teamed with higher octane fuel. Without the ignition timing advance changes, the fuel does not help make any extra power.
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  #11  
Old 02-20-2013, 07:49 PM
snowsled7 snowsled7 is offline
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Quote:
Originally Posted by Larrick View Post
Premium, meaning 91 octane?
Should there be an increase in gas milage?
Improvement from what? Running regular? I doubt you will notice much difference, worth a try since the car should run more efficiently.

Quote:
The knock sensors are there to retard the timing for the use of lower octane..True?
Is there any damage being done to an M50 vanos by running 87 octane aside from less power?
I do not necessarily want my son to drive any faster than he already does!
What type of gas milage should I be getting on a 1994 525i touring in mostly city driving?
You probably will not hurt it running lower octane. Do realize that the default is the ignition curve for premium and the knock sensors can not do anything until they sense actual knock, which is never a good thing.

The correct fuel is much better for the engine. I wouldn't expect much milage from an automatic in a touring. With a young man at the wheel... back in my day, I would have that wagon in the low teens for mpg

Type of driving and driver make all of the difference. It is capable of 19-20 in town and 27-28 hwy, just my guess, somebody probably has hard numbers.
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  #12  
Old 02-20-2013, 08:15 PM
Larrick Larrick is offline
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Every time I am in the passenger seat, I am imploring him to slow down, accelerate slower and stop changing lanes like he is are on a race track. I never listened at his age.
Why should he?
I tell him to treat the car like she is an old dear lady but He loves the way it handles.
I know I can better gas milage out of it.
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  #13  
Old 02-20-2013, 08:27 PM
rdc rdc is offline
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Quote:
Originally Posted by supertech777 View Post
My 95 525 with chip runs good on 91 but loves 93 , performance wise

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Agreed. I have the EAT chip and runs better on 93. I used to use Chevron until they pulled out of KY now i use Shell 93 which seems to get better mileage than most other brands. I have averaged 22.8 mpg overall per my records kept via fuelly.
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  #14  
Old 02-20-2013, 08:33 PM
snowsled7 snowsled7 is offline
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Sounds to me like a BMWCCA track day would either create a monster, or demonstrate to him that you honestly can not even come close on the road, when compared to the track.

After my first day in Porsche Club drivers ed, I drove home doing the speed limit. Believe me, that was rather abnormal... has become to some extent still. Great learning experience though, get him some real instruction. Accept that he will still probably push his luck. Feel good that you bought him a tank.

If he has to buy premium, maybe he wont ride it so hard.... Track milage, fill-ups, have him keep reciepts, good practice for life right there.

I definately have an opposite challenge. My son is scared of the 535. He is 16 in a few months, we have a loooong way to go before he is ready to drive.
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  #15  
Old 02-20-2013, 09:04 PM
Drew's525i Drew's525i is offline
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How is your son scared of a 535? I'd embrace it.
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  #16  
Old 02-20-2013, 10:03 PM
japbike736 japbike736 is offline
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Mein Auto: 1990 535i, 1999 911
My M30 5 speed gets 17 city 21 highway no matter what crappy California gas I use.....
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  #17  
Old 02-21-2013, 02:05 AM
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_Ethrty-Andy_ _Ethrty-Andy_ is offline
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Quote:
Originally Posted by Microtesties View Post
My M20 likes 93 octane, so that's what I use. Probably still a bit more expensive than regular, but it's better for the engine so it's worth it.
be carefull when talking about octane

some countries (like godsown New Zealand) use the RON system, whereas the USA use a different system, so depending on what you read take note of where it is coming from.

Here, 91 is regular, which is equivelent to your 87ish
Premium is 95 or 98 depending which brand you go to, which is equivelent to your 91
there is also super premium available here at some sites but thats an ethanol blend no good for most cars, and is over 100 RON

To keep it specific to E34:
1/ M20 M30 and M40 engined E34 require regular petrol as they DO NOT have the technology to take advantage of Premium. Anyone that says otherwise, im sorry but thats placebo.
2/ M50 and M60 E34 need Premium.

Edit: Here is some more reading on the octane debate and why your system is silly :P
http://en.wikipedia.org/wiki/Octane_rating
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Last edited by _Ethrty-Andy_; 02-21-2013 at 02:09 AM.
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  #18  
Old 02-21-2013, 07:00 AM
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Monsignor Monsignor is offline
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^very helpful andy. Thank you for the clarification.

Alot of tuners (being in the 350Z scene (hard to say that with a striaght face)) go E85 in their cars. Most fuels are blended 15% ethanol, E85 is, you got it, 85% ethanol. It requires a special tune obviously and new lines and hosing. They make absurd power but only really run right between 40-85 degrees. Alot of S2000 and Evo guys are the main players. Fun fact.
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  #19  
Old 02-21-2013, 07:02 AM
SwissCheeseHead SwissCheeseHead is offline
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Quote:
Originally Posted by _Ethrty-Andy_ View Post
be carefull when talking about octane

some countries (like godsown New Zealand) use the RON system, whereas the USA use a different system, so depending on what you read take note of where it is coming from.

Here, 91 is regular, which is equivelent to your 87ish
Premium is 95 or 98 depending which brand you go to, which is equivelent to your 91
there is also super premium available here at some sites but thats an ethanol blend no good for most cars, and is over 100 RON

To keep it specific to E34:
1/ M20 M30 and M40 engined E34 require regular petrol as they DO NOT have the technology to take advantage of Premium. Anyone that says otherwise, im sorry but thats placebo.
2/ M50 and M60 E34 need Premium.

Edit: Here is some more reading on the octane debate and why your system is silly :P
http://en.wikipedia.org/wiki/Octane_rating
We use a lot of silly systems. 75 degrees F, 5/16 of an inch, 10 lbs 3 oz...it's all stupid. METRIC FTW lol
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  #20  
Old 02-21-2013, 11:13 AM
txrealtor txrealtor is offline
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Quote:
Originally Posted by Larrick View Post
Premium, meaning 91 octane?
Should there be an increase in gas milage?
The knock sensors are there to retard the timing for the use of lower octane..True?
Is there any damage being done to an M50 vanos by running 87 octane aside from less power?
I do not necessarily want my son to drive any faster than he already does!
What type of gas milage should I be getting on a 1994 525i touring in mostly city driving?
I get 18 city and 24 highway. I did a 5 speed swap to my touring which affects the gas mileage slightly.
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  #21  
Old 02-21-2013, 06:46 PM
Larrick Larrick is offline
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I assume txrealtor that you are running 91 octane. The 91 octane at a "Westco" station is only 10 cents higher than 87 octane. At $4 a gallon in SanFrancisco (actually higher at most stations)
A 2 or 3% increase in milage would cover thew difference.
91 octane at the local 76 station is $4.39.....ouch.
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  #22  
Old 02-21-2013, 08:54 PM
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_Ethrty-Andy_ _Ethrty-Andy_ is offline
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Quote:
Originally Posted by Monsignor View Post
^very helpful andy. Thank you for the clarification.

Alot of tuners (being in the 350Z scene (hard to say that with a striaght face)) go E85 in their cars. Most fuels are blended 15% ethanol, E85 is, you got it, 85% ethanol. It requires a special tune obviously and new lines and hosing. They make absurd power but only really run right between 40-85 degrees. Alot of S2000 and Evo guys are the main players. Fun fact.
Wait, people are still rocking S2000's? i thought they were only any good in Need for Speed Underground 1!?!

Quote:
Originally Posted by SwissCheeseHead View Post
We use a lot of silly systems. 75 degrees F, 5/16 of an inch, 10 lbs 3 oz...it's all stupid. METRIC FTW lol
would be easier if you used New Zealand Dollars as well
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  #23  
Old 02-22-2013, 07:10 AM
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Monsignor Monsignor is offline
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the S2000 scene here in north east is pretty strong. albiet not as much as the evos/wrxs. I almost got into an S2K instead of my Z. but because i'm not a legal midget, i didnt fit. and i'm not big. 5'11 165lb
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  #24  
Old 02-22-2013, 03:06 PM
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_Ethrty-Andy_ _Ethrty-Andy_ is offline
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Quote:
Originally Posted by Monsignor View Post
the S2000 scene here in north east is pretty strong. albiet not as much as the evos/wrxs. I almost got into an S2K instead of my Z. but because i'm not a legal midget, i didnt fit. and i'm not big. 5'11 165lb
My grandperants were going to give me their Mazda MX5 when i graduated high school but i couldn't fit into it comfortably. they are super nice to drive though.

The scene here is much more Nissan focused than others, wannabeEvos are common, subareas not so much. Lots of R32 R31 C33 etc Nissans here. Also the Holden VL Commodore which runs a nissan RB30 are quite common too though slow.
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  #25  
Old 02-22-2013, 03:14 PM
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Monsignor Monsignor is offline
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Quote:
Originally Posted by _Ethrty-Andy_ View Post
My grandperants were going to give me their Mazda MX5 when i graduated high school but i couldn't fit into it comfortably. they are super nice to drive though.

The scene here is much more Nissan focused than others, wannabeEvos are common, subareas not so much. Lots of R32 R31 C33 etc Nissans here. Also the Holden VL Commodore which runs a nissan RB30 are quite common too though slow.
Aren't holdens GM? what are they doing with nissan motors?
Nissan skylines are illegal in the States. They get crushed if you have one. Its a damn shame really. Soon the R32 will be 25 years old, making it legal to import because it'll be a historic.

I love my nissan, its an absolute animal in every regard. Throwing that little screamer everywhere never fails to please.
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