E89 2.5 Jap import only runs on 98

[First Timer 22]

Many members telling me i can put 95 RON in my Jap import E89 but if i do it then the engine light turns on. car runs fine. once i fill in 98 RON the error goes away. according to the local BMW they say there are no faults and I should be able to use 95 RON. 

any advice?

[NZ00Z3 187]

The engine light will have an associated trouble code.  What is the code number and description?

If it is a mixture related trouble code:

• Record the 4 fuel trims when on 95, both at hot idle and at steady 100 kmph.
• Record the 4 fuel trims when on 98, both at hot idle and at steady 100 kmph.
• Post the fuel trim results here.

[jon dee 500]

Checking for codes is the easy first step. You just need to find someone with a BMW OBD2 code reader. 

How many km has the car done ? The difference in octane rating is not that great, so to get an engine light when changing fuels one of the parameters that the ECU monitors must be hovering near the tripping point. Maybe something like incipient knock. Do you feel any loss of power as if the ECU was pulling timing when the light comes on ? 

Cheers... 

[M3AN 4016]

I can't imagine a scenario when you'd want to regularly run a boosted engine on 95, I think the answer to the OP's question is: you need to use 98, your car has already told you that, the codes will simply confirm the same, don't pay somebody $60+ to find out.

If you've posted in the FI section just for fun and actually have a NA N52 then you're still better off running it on 98 than 95, especially if you like to use a heavy right foot. Admittedly my N52 is tuned and I cringe if I have to use 95 and only ever half fill it and then dilute it with 98 as soon as I can.

Edited March 4, 2022 by M3AN

[Jacko 2156]

My 130 throws cat check errors on less than 98, since I reset the DME adaptation on 98. Could be similar, but as above... what are the codes.

[First Timer 22]

i don' t have any codes. this is only my 2nd BMW in 40 years. the first was a 2002tti. (never should have sold it!, lol) all i know is if i put fuel under 98 RON then the engine light comes on. supposedly it only has about 200 hp but it does 0-100 in 6.1 it only has the N52K inline 6. if it's overtuned i'd like to put it back to factory specs so i have the reliability.

[NZ00Z3 187]

Where in the South Island are you?  I'm in Timaru.

[Jacko 2156]

7 hours ago, First Timer said:

i don' t have any codes. this is only my 2nd BMW in 40 years. the first was a 2002tti. (never should have sold it!, lol) all i know is if i put fuel under 98 RON then the engine light comes on. supposedly it only has about 200 hp but it does 0-100 in 6.1 it only has the N52K inline 6. if it's overtuned i'd like to put it back to factory specs so i have the reliability.

Get it scanned, or better yet get bimmergeeks protools (its worth it) and see what its doing. Getting a decent scan tool is pretty much mandatory purchase when buying a BMW of this vintage, removes 99% of the guess work. 

You wont bust it running a map, unless its a horrendous one. It might have a 130i map on it or something (which are available online for free). 

Edited March 10, 2022 by Jacko

[NZ00Z3 187]

What make of 95 and 98 fuel do/did you use? 

I know this sounds like a silly question in the N.Z. context, but I've just learnt on another BMW forum, that the various E10 fuel grades give a 5% lean offset of the fuel trims.  Could it be that the 95 was E10?  Is that product even available in N.Z.?

Edited March 10, 2022 by NZ00Z3

[dirtydoogle 383]

Are you sure you did the fuel cap up correctly? Thats more likely to throw an EVAP code that self clears. 

Maybe try bash some 95 in it again

[First Timer 22]

i downloaded the my BMW app based on my vin. the personalised owner's manual says the car requires greater than 95 Ron fuel and a minimum of 91. the manual says the engine light will be present but not blinking due to excessive emissions. if the engine light is blinking then pull over because there is is risk of engine damage. does this mean i have the 217 bhp version? the personalised manual doesn't quote hp specs.