View Full Version : Feedback on Octane

Dan Burger
04-06-2001, 08:01 PM
Anyone have any exp. running anything less than 91 oct. with a chip? I hear it's "highly not recommended" by Jim C. among others.
'95 CS

04-20-2001, 11:40 AM
I was running 87 without a chip and was getting pretty ****ty gas mileage. I just noticed on the cap that it requires 89+! I'm a dumbass! I now put 92-93 octane in and get fairly good gas mileage. Stay with the higher octane.

06-16-2003, 02:42 PM
My JC'ed e30 trained me to use high octane, so when I got my ti, I automatically started putting 91 in it, with stock software. The few times I've topped off with 87, it seems like I get slightly worse gas mileage, and I think I can feel the knock sensors retarding timing on real hot days.

That said, I think the use of highest octane possible is VERY sound advice when you're running a chip...I know of a few people that can't even run 91 without throwing CELs w/JC chip.


06-16-2003, 05:39 PM
I always ran 93, with good luck as far as mileage and no problems with any fuel related parts (injectors, filters etc.)

I just recently started using 94 in the Dinan chipped 3.2, and it felt like adding 10 HP! I can't believe the difference 1 octane point can make!

Run the 93 in the stock car. It will pay dividends.

07-23-2004, 05:53 PM
Use the lowest octane you can without knocking (or triggering knock sensor), otherwise you waste money. That might be 91, that might be 89, it might be 93. I would avoid ethanol in the summer, I experienced stalling and poor fuel economy when I used it in hot weather.

Octane rating requirements will go down when elevation increases, typical is around 1 point per 1000 feet of elevation. That is why if you go to high elevation areas, the highest octane available might be 89 or 91. Where I used to live in Wyoming at 7200 feet, we had 85/87/89 for the most part. This is because the air is thinner and the car effectively has a lower compression and will produce less power (about 3%/1000 feet) so at 7000 feet, the car has 21% less power (a 200 hp car would have about 160 hp at 7000 feet) .

I run 89 in my stock car without any trouble. I get 23/31 mpg and full performance. Try the three out and see if you feel a difference. Outside temperature/humidity and other factors can have an impact on what octane you need.

Anyone have any exp. running anything less than 91 oct. with a chip? I hear it's "highly not recommended" by Jim C. among others.
'95 CS

07-25-2004, 12:28 AM
We always use the 98 RON BP Ultimate where ever possible.

07-26-2004, 06:28 PM
That is another good point, the RON octane rating is different from U.S. CLC octane rating, I think a 98 RON is about 93 CLC. Many european cars list only the RON rating, so it might say use only 93 RON octane fuel, but in the U.S., you would only need to use 89 octane.

We always use the 98 RON BP Ultimate where ever possible.

07-29-2004, 11:22 AM
Yeah..........there is a difference in the europian rating......here in Bulgaria, da lowest octane is 95.....today I`v tryed a 100 octane fuel imported from Greece.....it is really good.....and da consuption went down.......the price is 1 EUR per liter :lol: :lol:

07-29-2004, 05:52 PM
the price is 1 EUR per liter :lol: :lol: In the U.S. we complain when gas is $2.00 US / gallon, or about $0.53 US / liter, or about 0.44 EUR per liter. We are cheap when it comes to gas. Americans would not know what to do if we ever had to pay 1 EUR per liter ($4.60 / gallon). I guess we probably wouldn't buy as many 300+ horsepower/ 223 KW cars and we would buy more cars like the 318ti.

09-25-2004, 01:42 PM
well if youre that cheap to get 87 octane why did you buy a BMW. Youre only saving on average 2.00 a tank if you put the lower grade gas in. Just put in 93 its not that big of a price difference. Is it really worth saving a couple of bucks each time you fill up and run the possibility of blowing the engine???

09-25-2004, 08:28 PM
eh, i suggest just sticking with the 89 if your car is stock. you may need higher if you have a chip or higher compression.

and there's not really a problem with running 87 besides reduced performance. our cars have knock sensors and will retard the timing long before the engines detonate themselves apart. but doing that will reduce your power and possibly the gas milege, and will ruin the point of buying cheaper gas.

09-25-2004, 09:03 PM
I run the cheapo 87 octane and I get about 28 mpg around town. I'm also a poor college student. Maybe once my background check comes back and I get hired I will start putting more expensive stuff in my car.

09-26-2004, 03:21 PM
i use the middle stuff...for a while i had used lowest stuff but then i saw the gas cap said use at least 91 (maybe...whatever the middle one around here is) so now i use middle

09-30-2004, 03:40 AM
follow up on an octane question....... What if you run 91+ oct, and add 104 octane boost to the mix?

09-30-2004, 06:06 AM
follow up on an octane question....... What if you run 91+ oct, and add 104 octane boost to the mix?

The octane level will increase depending on how much was added.

A simple formula to work it out would be

(91 octane * litres) + (104 octane * litres) / total litres

I hope this helps :)

09-30-2004, 07:29 PM
my first tank on my BMW was 87 octane, I was just out of habit from my other car, sure it ran fine and all but the milage wasn't what it could have been.

From the second tank on out I went to the recommended 89 and I noticed great gas milage on a 220 mile trip to school I got 35 -37 MPG

Last time I went home I stopped at a gas station, and guess what they were out of 89 so I wasn't going to put in 87 and I wasn't going to a different station, so I put in 93.

The results of 93 from the 220mile trip home are 39 - 39.5 MPG

From this point out I am running premium only, what is another $2.00 at fillup when you make it up in milage.

I am not one to complain about gas prices and probably never will because I look at the alternatives.