Fuel 98/95 RON?

[13eastie]

Does anyone know the performance implications of using 95 RON unleaded as opposed to the recommended 98 RON?

[lucid]

If 98 is required for this engine, it will eventually knock under WOT conditions, your ECU will adjust ignition timing to avoid knocking, and you will lose power.

[13eastie]

Originally Posted by lucid

If 98 is required for this engine, it will eventually knock under WOT conditions, your ECU will adjust ignition timing to avoid knocking, and you will lose power.

Sure, but has the power loss been quantified anywhere?

[lucid]

Originally Posted by 13eastie

Sure, but has the power loss been quantified anywhere?

I have no idea how much of a loss that would be if that is what you mean. It also depends on the specifics of the code the ECU is running. I can dig around an IC engines textbook I used to deal with 15 years ago in search for a theoretical answer...

[13eastie]

Originally Posted by lucid

I have no idea how much of a loss that would be if that is what you mean. It also depends on the specifics of the code the ECU is running. I can dig around an IC engines textbook I used to deal with 15 years ago in search for a theoretical answer...

That would be awesome. Cheers.

[OzStriker]

98 FTW

[lucid]

Originally Posted by 13eastie

That would be awesome. Cheers.

Eastie, I did look this up, and there was a section in the book. There is no simple answer as they cite 10+ variables that affect the combustion dynamics during knocking. However, torque loss clearly seems to be a function of spark advance and engine speed. The loss that results from retarding the spark advance can vary from 10% at low rpms to 1% as the engine reaches the higher rpms. This is a pretty general statement though, and does not necessarily directly address the 95/98 scenario.

[JEllis]

98 is difficult to find in Cali

[lucid]

What is the octane requirement for the engine exactly?

[JEllis]

^ What he said!

[lucid]

I missed the "recommended" part...

[mkoesel]

Originally Posted by JEllis

98 is difficult to find in Cali

But 98 RON isn't the same as 98 Octane.

Most likely the motor will require premium fuel in the US, i.e 91 Octane (or 90 in some states, as I found out on a road trip once).

[lucid]

Originally Posted by mkoesel

But 98 RON isn't the same as 98 Octane.

Most likely the motor will require premium fuel in the US, i.e 91 Octane (or 90 in some states, as I found out on a road trip once).

RON is an octane rating. So is MON. In Europe, they use RON. In the US, we use (RON+MON)/2. They are different measurement methods to get at the same thing. I believe 98 RON translates to about 93 (RON+MON)/2 in the US. I dount that that will be the recommended rating for the US though.

[mkoesel]

Originally Posted by lucid

RON is an octane rating.

Ok true. My point to JEllis, though, was that 98 RON in UK does not translate to "98 Octane" in California.

[13eastie]

http://www.thorneymotorsport.co.uk/c...ull-290806.pdf

[GregW / Oregon]

Originally Posted by mkoesel

But 98 RON isn't the same as 98 Octane.

Most likely the motor will require premium fuel in the US, i.e 91 Octane (or 90 in some states, as I found out on a road trip once).

Premium in the US is typically 93 Octane. This is from the Chevron website:

"Q. How many grades of gasoline are available?

A. Most places that sell gasoline offer three octane grades of unleaded gasoline--regular at 87 (R+M)/2, midgrade at 89 (R+M)/2, and premium at 93 (R+M)/2. In high-altitude areas such as the Rocky Mountain Region of the U.S., the (R+M)/2 number may be lower by one or two numbers."

[mkoesel]

Originally Posted by GregW / Oregon

Premium in the US is typically 93 Octane. This is from the Chevron website:

I think that might be fairly Chevron specific. In my area, most gasoline labeled "Premium" is 91. Sometimes 92 or 93 also. And Sunoco has the Ultra 94.

I doubt there is a standard for the nomenclature "Premium" however. At the same time, I doubt BMW will recommend anything over 91 for this car. Can anyone point to a non-exotic car that actually recommends above 91? I am not saying there is not one, but I will be interested in hearing which car that is.

[lucid]

Cool data eastie.

[13eastie]

Originally Posted by mkoesel

I think that might be fairly Chevron specific. In my area, most gasoline labeled "Premium" is 91. Sometimes 92 or 93 also. And Sunoco has the Ultra 94.

I doubt there is a standard for the nomenclature "Premium" however. At the same time, I doubt BMW will recommend anything over 91 for this car. Can anyone point to a non-exotic car that actually recommends above 91? I am not saying there is not one, but I will be interested in hearing which car that is.

In Europe RON 95 (equivalent to 91 AKI) is the lowest octane petrol generally available.

It's possible that manufacturers simply do not recommend higher ratings in the States because (un)availability might put customers off.

From the U.K. M3 Brochure:

The petrol engine is designed for RON 98 fuel and may be run on RON 95, with a decrease in power.

[lucid]

What's the price difference between RON95 and 98 in the UK?

[13eastie]

Originally Posted by lucid

What's the price difference between RON95 and 98 in the UK?

Where I live:

RON 95 95.9p
RON 98 102.9p

So it is just over a 7% premium, but if you do get a 10% power improvement, the effetive cost difference could be negligable.

[southlight]

Problem here in Germany is that RON98 is no more available at the big stations, either 95 or Ultimate/VPower (means RON100). That bothers me, especially since the current premium for Ultimate is 13 cent (makes 1.50 € per liter).

Best regards, south