Octane question

[Shade Tree]

I have a 1992 525iT (Wagon) and my wife mixed a half tank of regular with 1/2 tank 92 octane. She thinks premium is too expensive...

The manual says premium. Is this a problem and what happens if I use regular?

[JAlfredPrufrock]

If there is no pinging there should be no problem...

[bimmerd00d]

use premium, it's what the car is designed for. It might or might not mess it up, but you eliminate that chance by using the correct octane.

[jplacson]

Well, it's not really a big problem. But here's just my observation. I tried the 92 octane once since it was cheaper... car ran a bit sluggish, but it was generally fine.

Switched back to 95 (and sometimes 96) octane since the car felt much better to drive on 95.

The one thing I DID notice... my fuel consumption went down when using the higher octane... I actually got a lot more miles (or km/l rather) to the gallon using 95 octane. Enough that in the long run (past 2 full tanks) running 95 octane is actually cheaper than running 92 octane. At least for me.

So that may be something to consider... not to mention your car will perform the way it was intended to. :)

[632 Regal]

low octane burns quicker and cooler, same thing as advancing the timing a couple degrees. I wouldnt be going against a recommendation though, stick with the correct octane. Lower octane can produce detonation that is hard to detect with your ears and beat the piss out of everything from the pistons to the crank.

[bimmerd00d]

i dont believe the '92 M50 non-vanos had knock sensors, that came with VANOS i think. may not adjust timing to the lower octane.

[Interceptor]

I have a 1992 525iT (Wagon) and my wife mixed a half tank of regular with 1/2 tank 92 octane. She thinks premium is too expensive...

The manual says premium. Is this a problem and what happens if I use regular?

Hm... I'm always fascinated by people who drive bimmers and try to save on fuel... Maybe they should drive a diesel Honda? :)

Anyway, DO NOT use regular fuel in your car. I have the same car (only the saloon version) and using anything other than 95 RON fuel makes it go worse, consume more fuel and start harder on cold starts. The higher the octane, the fuel is generally cleaner and has less sulphur. At least here, in Europe.

Regards

[jplacson]

There's nothing wrong with trying to save fuel. This isn't the dark ages anymore where the more gas you burn, the cooler you are. That mentality should be reserved for American cars. :lol: Bimmers are meant for optimum performance... they shouldn't burn more fuel than needed to give out the performance needed.

I'm not saying they are economical either... Bimmers just aren't wasteful. Maybe that would be a better term for it since "saving fuel" seems to be a faux pas to some Bimmer owners. Bimmer drivers don't WASTE fuel. (We just burn it faster than most... hehehehe)

[liquidtiger720]

im stuck with 91 =p and all you guys are talking about are 92's and 95's...I envy you.

[Nzimiro]

im stuck with 91 =p and all you guys are talking about are 92's and 95's...I envy you.

Hi all,

This is my 1st post on this forum, though, I have been a regular visitor since August last year and I have picked up quite a lot information on my 540i/A, thanks to you all. This thread interests me hence my decision to resgister today.

Liquidtiger, you are even luckier than me - my fuel grade is usually 88/89! I have heard of octane boosters - sold next to fuel injector cleaners. Has anyone else heard of them? Do they really work?

Regards
Nzimiro

[Mobius]

im stuck with 91 =p and all you guys are talking about are 92's and 95's...I envy you.There are two methods to measure octane. Here in the US, we average the two. In Europe, they use only the higher of the two (which I think is RON - here we do (RON+MON)/2).


Liquidtiger, you are even luckier than me - my fuel grade is usually 88/89! I have heard of octane boosters - sold next to fuel injector cleaners. Has anyone else heard of them? Do they really work?No. Octane Booster in a can is usually just toluene. On the side of the can it will usually say "will raise octane by one point!" - which means, if you started with 89, after the bottle, you might have 89.1. In order to actually make an appreciable difference in the actual octane of the gas in your tank, you'd have to add gallons of the stuff.

[632 Regal]

right, if it was that easy and cheap to add octane points every station would have 100 octane at the same cost ans regular.

[atomicDog]

I have a 1992 525iT (Wagon) and my wife mixed a half tank of regular with 1/2 tank 92 octane. She thinks premium is too expensive...

The manual says premium. Is this a problem and what happens if I use regular?

ShadeTree, for what it's worth, I run mid-grade (91 octane) fuel in my 1995 BMW 525iT wagon. Runs great in the winter and cool days. During the summer or during heat & humid days, I notice that it pings slightly on take-off. Fuel mileage averages 21 - 22 MPG in mixed city/highway driving.

[MarkD]

im stuck with 91 =p and all you guys are talking about are 92's and 95's...I envy you.


They are using the RON octane rating system, not AKI as used in North America. Subtract 4 from the RON to get the approximate AKI rating.

Example:
98 RON = 94 AKI
95 RON = 91 AKI
91 RON = 87 AKI

Now you shouldn't feel so bad. :)