Hey guys,

I recently purchased a BMW 118i sport. I have been filling it with BHP ron95 from day 1. However, I have been doing a lot of reading about ron95 and ron97 now I am totally confused. I read up that my engine ratio is 11.1. However in the manual the recommended is ron95. I would like to know if there would be any benefit to use ron97 compared to ron95.

1. in terms of the engine being cleaner
2. fuel consumption
3. power

Hope that all those who are in the know regarding compression ratio's and the proper ron to share some knowledge with me. Thank you.

You using the B38 1.5 L 3 cylinder engine?

If yes.. Ron 95 is FINE.....

I drove the 218i Active Tourer.. the engine quite robust it can take as low as RON 91 onward..

Anyway.. I did pump with Ron 97 and no different... according to my friend working in BMW .. no point putting higher Ron.. the GDI engine will have carbon build up anyway irregardless what type of fuel it consumes.

Yes it is the B38 engine as far as my research. It is the 1.5 L 136 bhp engine. Mine is a 118i sport. Yes, so what did your friend at BMW suggest? Fuel injector cleaning? if so how often? Thanks a lot.

Above in bold are my comments in relation to your question points.

As has been discussed many times before, basically if the car is already optimized to run on lower RON then there's no benefit whatsoever running higher RON! That will be just a total waste of money.

Compression ratio is a major factor in determining how much RON you need but in this modern days of technology, there are already plenty of sophisticated engine design, tuning, & mapping to enable using lower RON requirement than in the olden days. So to make it simple just use the RON already recommended by the manufacturer, they should know best already.

Those cleaning agents that you put into the tank will not work especially for GDi engine since the fuel is sprayed directly into the combustion chamber, by passing the valves and intake where there can be more the carbon build up. At best those agents will just help clean the injectors and piston top but that's it. So you need to do specific carbon cleaning service whereby the mechanic will need to open up the intake and spray the cleaners into the intake and valves.

alright thanks a lot.