Best Fuel Grade to use in 1991 850i

[m6bigdog]

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.

Sounds simple but few things are more complex:

Your question:
can you safely run 89 with ethanol in a 97 840ci ?
I would not. I would say: use 91 AKI (which will include some % ethanol) and always follow the manufacture specification.

Also, Trying to save a few bucks on gas often caused other more expensive engine problems like carbon build up in the combustion chamber or on valves.
I drove a E38-740-M62B44 like I stole it for 178K miles on Chevron premium (91 Octane) 90 MPH runs up/down I-5 in summer. With 3k oil changes - I never needed to add a quart of oil and the engine ran smooth as silk when I gave the car to my son in 2015; who still drives the 740!!

I'm sure you will find the info below in the 1997 840 owners manual:
Minimum octane requirement: 91 AKI.
BMW engines are equipped with knock
sensors and will adapt automatically
to different octane ratings, provided
that the minimum octane requirement
(87 AKI) is met.
Fuels with higher octane ratings will
provide enhanced performance and
lower fuel consumption, while the use
of fuels with lower octane ratings will
have the opposite effect.


Gasoline refining and production (blend package) has State (California), Federal (US) as well as a Global (country) standards.
Vehicle manufactures rely on these Fuel standards and owner adherence to the vehicle fuel specifications.
However, beyond the Octane rating, what you can buy is largely dependent on where you live.
What also complicates the comparative octane rating issue is American Octane rating: Anti-Knock Index (AKI) or (RON+MON)/2 where as in Europe they use RON only

I am unsure what you mean by "true gas locations" is this pure non-ethanol gas?
I found this sight for California: (only 23 pure non-ethanol stations listed)
https://www.pure-gas.org/index.jsp?stateprov=CA
I anticipate this is some very expensive gas!! as it will use a more expensive fuel blend to get around using ethanol as the federally mandated oxygenate.

For a deep dive:
https://en.wikipedia.org/wiki/Octane...,_MON,_and_AKI
Octane rating

https://www.epa.gov/gasoline-standar...ne-regulations
Federal Gasoline Regulations
"The Clean Air Act requires EPA to regulate fuels and fuel additives for use in motor vehicle, ... engines to reduce harmful emissions."
"Gasoline regulations are under 40 CFR Part 80 (“Regulation of Fuels and Fuel Additives”): subparts A (general provisions, applying to all 40 CFR Part 890 fuels programs), B (controls and prohibitions), C (oxygenated gasoline), D & E (reformulated gasoline), G (detergent gasoline program), H & O (gasoline sulfur) and J & L (gasoline toxics)."

https://www.arb.ca.gov/fuels/gasoline/faq.htm
Frequently Asked Questions about the California Reformulated Gasoline Program
3. How much ethanol was required in gasoline under the Federal Energy Act for 2008?
The Energy Independence and Security Act of 2007 requires that fuel producers must increase their use of renewable fuels every year through 2020. For 2008, this effectively corresponded to a required national average ethanol content of 7.76 percent by volume.
4. Will the Federal Energy Act requirements increase ethanol content in gasoline to 10 percent by volume?
Yes. We expect that the Federal Energy Act requirements will lead to a required national average ethanol content of 10 percent ethanol by 2012. However, California has had 10 percent ethanol in it's gasoline since the beginning of 2010.


https://www.eia.gov/tools/faqs/faq.php?id=27&t=10
From: U.S. Energy Information Administration (EIA)
Most of the gasoline now sold in the United States contains some ethanol. Most of ethanol blending into U.S. motor gasoline occurs to meet the requirements of the 1990 Clean Air Act (RFG Fuel) and the Renewable Fuel Standard set forth in the Energy Independence and Security Act of 2007

All gasoline engine vehicles can use E10. Currently, only flex-fuel and light-duty vehicles with a model year of 2001 or newer are approved by the EPA to use E15. Flex-fuel vehicles can use any ethanol-gasoline blends up to E85.

FWIW:
The energy content of ethanol is about 33% less than pure gasoline. The impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol. The energy content of denaturant is about equal to the energy content of pure gasoline. In general, vehicle fuel economy may decrease by about 3% when using E10 relative to gasoline that does not contain fuel ethanol.

[Fatandre]

I never go the answer if I actually benefit on the s70 from using ron 98 or higher octane fuel

[Fatandre]

Just bumping this.

[Timm]

I don't know enough about the S70 to give a definitive answer - if the S70 has knock sensors, then (like the V8's) the DME's can advance the timing to the point just before detonation to utilise the fuel to its full potential. With a higher knock-index fuel the timing can be advanced further providing more power.

If you don't have knock sensors then utilising a fuel with the higher AKI makes no difference at all - the timing is fixed to the DME tables and the 'better' fuel will not make a jot of difference unless those tables are altered with a custom 'tune'. In that case, the fuel grade specified on the filler flap will do nicely!

[the green amigo]

I have a wokke chip installed on my 93 850ci, website says to use premium fuel, 93 or similar. All the info here says to use 87. Which is correct?

[Laserface]

Use 93 with the chip.

[TxGR8White]

M70 with V2 chips, and I run 87, works perfect and is fast too. You only need higher octane if you are using forced injection or have increased the compression (both of which are’t happening with Wokke chips).

[Laserface]

According to wokke's website, the V2 chip is optimized for 95 RON. That's 91 octane in the US.

[usce]

FWIW i noticed someone mentioned in this thread that there is no ethanol free fuel in Florida ... there is indeed i put it in my boat its 90 AKI says Rec Fuel on the pump