Best Fuel Grade to use in 1991 850i

[jaydog101]

I read the octane posts and chose to start using 87 and I had problems with my car going into limp mode in the mornings. So of course I was told to rebuild the DK's so I got some from Tom. While waiting for the motors I decided to run some 93 octane and my car has not started up in limp mode since. So I still haven't installed the new DK's after being told that only having 60,000 on my 8, they were probably fine.

So anyway no tech talk here just some info from experience.

[bRIZZAd]

A side note to this, not sure if related or not at this point. I had the 8 out this weekend for a long road trip and ended up having to fill with 91, as the station was out of 87. Immediately following this, the 8 ran a needle width tick above 12 o' clock while before it was a needle width below as per normal.

[EEDegreeToDrive]

Running 10% Ethanol is not a problem at all. I've been running 85% in my E31850, E34-540 as well as E39-520 and E39-523. The only problem has been poor idle for the first few minutes due to the 30% lower energy content of Ethanol compared to gasoline.

Wokke--
Do you still run E85? Does it run well in your car?

Being a higher octane equivalent, have you found it to be worthwhile? Does the E85 'clean' out your engine/injectors?

Do the Wokke chips impact the ability to run E85? Are there any other considerations?

I usually always run 87 octane, but every 5-6th fill up (or If I have full load of stuff, climbing a lot of hills, etc) I'll use 89 and once in a blue-moon, Shell 93 (differential price is cheaper than a pint of injector cleaner)

[wokke]

Wokke--
Do you still run E85? Does it run well in your car?

Being a higher octane equivalent, have you found it to be worthwhile? Does the E85 'clean' out your engine/injectors?

Do the Wokke chips impact the ability to run E85? Are there any other considerations?

I usually always run 87 octane, but every 5-6th fill up (or If I have full load of stuff, climbing a lot of hills, etc) I'll use 89 and once in a blue-moon, Shell 93 (differential price is cheaper than a pint of injector cleaner)

No, I'm not running E85 anymore. The last time my engine ran like shit. Although from the same gas station it appeared to be of much much lower quality that what I used before. I actually had to cheat the DMEs via the water temp sensor to tell them that the engine is ice cold in order to get enough fuel into the cylinders. Due to the much higher fuel consumption (E85 has about 30% less energy per volume) it also didn't make any worth while difference in my wallet. I even tried different chips with 5° more pre ignition but didn't help. So I can't recommend it although the engine runs quite a bit smoother on E85.

[Racer MXM]

I enjoyed the back and forth on this thread. For me unfortunately in Saudi Arabia, we only have the choice of 91 or 95 (in Dubai its 95 or 98), but lucky for me gas is only 60 cents a gallon for 95 and 91 is 40 cents a gallon

[btnh]

WOW, those are amazing gas prices! . lol... 98 in dubai, really?

[Racer MXM]

yup 98 in dubai for like AED1.60 a liter which is like $0.40 so if u figure 4 liters to a gallon then its like saying $1.60 for a gallon of 98 octane

[CaifanSC]

gas is only 60 cents a gallon for 95 and 91 is 40 cents a gallon

WTF! Unreal!

Lucky man

[sleepy81]

I actually had to cheat the DMEs via the water temp sensor to tell them that the engine is ice cold in order to get enough fuel into the cylinders. Due to the much higher fuel consumption (E85 has about 30% less energy per volume)

Wolf, my 2 stroke race engines require about 50% larger main jet to use E85 over RF100 so no surprise you had to tweak to get it to run. I would not recommend E85 for road use due to the high consumption (if you could get it to run OK) and for me, all ethanol based fuels have the natural propensity for water absorption so I avoid like the plague except when I can buy in sealed containers.

[Redbmw840]

thanks for the Question....

My car is a EURO 840 Ci 1995
4 liter M60 B40 engine
I have been using Shell V Power petrol (RON 98) in Hong Kong for the past 6 months of ownership.
I never realized until now that I was wasting my money so I will just start to use unleaded (95 RON) ... there is nothing Lower than (95 RON) here in Hong Kong

[rexdoss357]

than why is it when I used the 102 octane that's available at one gas station here my buick ran like a racecar leading me to think higher octane=more power

[8Harry8]

Your Buick is able to read, an 8 (M70) is blind and doesn't know what is written at the fuel dispenser.

No, just kidding, I bet your Buick has knock sensors and the engine management is able to react...

[hmfoster]

Have not seen a recommendation for the 96-97 840 . Where I live we have 86, 88 and 91. What is the proper to use. Thanks

[TxGR8White]

Have not seen a recommendation for the 96-97 840 . Where I live we have 86, 88 and 91. What is the proper to use. Thanks

Premium Unleaded

[hmfoster]

Thanks

[Fatandre]

reviving an old thread.
What about the S70? Should I be using EU98 octane or is it fine to run 95?

[kiwiCSi]

reviving an old thread.
What about the S70? Should I be using EU98 octane or is it fine to run 95?

The CSi owner's handbook and tank filler placard call for 95 octane minimum.
I use BP Ultimate 98 octane.

[Fatandre]

But does it Have knock sensors?

[kiwiCSi]

No knock sensors, but it's a high compression engine (9.8:1), hence the requirement for high octane fuel.
M73B54 engine is similar (10:1 compression ratio) and also requires minimum 95 octane.

[Fatandre]

So it would be even better to use 100 octane fuel

[Major Cheese]

The gas cap from my S70.

850CSi gas cap.JPG

[kiwiCSi]

Are you sure that's the original fuel cap for your CSi?
Last time I checked, 91 octane didn't qualify as premium unleaded.

[Edit: have inserted a page from the S70B56 engine manual].

[mbarrett635]

Are you sure that's the original fuel cap for your CSi?
Last time I checked, 91 octane didn't qualify as premium unleaded.

That's the AKI octane number. The owners manual usually lists the RON octane number that is used in Europe. The AKI number is around 4-6 lower than the same RON octane number.

Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)
Another type of octane rating, called Motor Octane Number (MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON, but there is no direct link between RON and MON. Pump gasoline specifications typically require both a minimum RON and a minimum MON.

Anti-Knock Index (AKI) or (R+M)/2
In most countries, including Australia, New Zealand and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2. It may also sometimes be called the Posted Octane Number (PON).

Difference between RON, MON, and AKI
Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's Sensitivity, and is not typically published for those countries that use the Anti-Knock Index labelling system.

"EuroSuper" or "EuroPremium" or "Regular unleaded" in Europe, "SP95" in France, "Super 95" in Belgium

RON 95

MON 85–86

AKI 90–91

Also, you should use the octane rated fuel that your engine needs, but there is no benefit from running higher octane; you're just wasting money. The octane level is designed to prevent detonation; higher octane fuel doesn't provide more power. Instead, using too low an octane rated fuel robs power by causing detonation (knocking) -- hence, AKI or "Anti-Knock Index".


Mike Barrett

[kiwiCSi]

That's the AKI octane number. The owners manual usually lists the RON octane number that is used in Europe. The AKI number is around 4-6 lower than the same RON octane number.

Thanks Mike - great explanation of the 'AKI' - which I wasn't aware of here downunder!
This means Major Cheese's gas cap sticker is absolutely correct, as 91 AKI translates to approx 95 RON.

Also, you should use the octane rated fuel that your engine needs, but there is no benefit from running higher octane; you're just wasting money. The octane level is designed to prevent detonation; higher octane fuel doesn't provide more power. Instead, using too low an octane rated fuel robs power by causing detonation (knocking).

Which is why higher octane fuel is specified for higher compression engines without knock sensors.

[neverl8]

Back when I was young, we called detonation off of compression alone a misfire.
Lower octane is more volatile under compression than higher octane. this is pretty rudimentary stuff.

This is why the lowest grade engines, Diesel, don't use spark plugs. It's such unrefined fuel it ignites simply off of compression.

My question is can you safely run 89 in a 97 840ci with ethanol? I use gasbuddy to find true gas locations.

What I was looking for and found this forum was a conversion chart for euro fuel ratings to make sense of my gas cap's value and what that translates to at a US pump.
I amazingly have not found a converter, calculator or forum which performs both of these tasks... crazy.