[TodmordenLad]

Apologies if this topic has been done to death already, guys....
Am picking up my new 440i GC in a couple of months and keen to know whether 440i drivers are using standard 95 RON unleaded or the higher RON, premium fuels available from Shell, BP et al.
If you're using 'super unleaded', are you noticing any difference in terms of performance and/or mpg?
Thanks

[HighlandPete]

Originally Posted by TodmordenLad

Apologies if this topic has been done to death already, guys....
Am picking up my new 440i GC in a couple of months and keen to know whether 440i drivers are using standard 95 RON unleaded or the higher RON, premium fuels available from Shell, BP et al.
If you're using 'super unleaded', are you noticing any difference in terms of performance and/or mpg?
Thanks

I typically use 95 RON (UK) in my 535i, as locally the premium options are a bit limited to RON 97 at very inflated prices.

If I fill with RON 98/99 (like Momentum), then definitely notice the difference. Either with better mpg in same style driving, or extra punch on hard acceleration, gearbox responds differently, more instant and harder changes. Block changes on kick-down are more brutal. Also mid range torque is better, that reflects in slightly different change points for given throttle inputs.

Any mpg benefits are more evident in steady speed driving, than normal short trip local stuff.

Remember the engines are designed around the higher octane ratings, (98 RON from BMW data), optimum power is therefore developed on the premium fuels. Slight loss of power on lower octane ratings.

[TodmordenLad]

Thanks Pete, very helpful ...particularly the last para., I had no idea.
Having filled up at the black pump for the last twenty years, I need re-educating

[HighlandPete]

Originally Posted by TodmordenLad

Thanks Pete, very helpful ...particularly the last para., I had no idea.
Having filled up at the black pump for the last twenty years, I need re-educating

The petrol engines have knock sensors which monitor combustion in real time. Lower octane requires a slight adjustment of ignition timing, this retarding of the ignition to control knock reduces the peak power.

[bavarianride]

Originally Posted by HighlandPete

The petrol engines have knock sensors which monitor combustion in real time. Lower octane requires a slight adjustment of ignition timing, this retarding of the ignition to control knock reduces the peak power.

So prolonged usage of RON 95 will not cause any damage to BMW engines designed for RON 98?

[HighlandPete]

Originally Posted by bavarianride

So prolonged usage of RON 95 will not cause any damage to BMW engines designed for RON 98?

No damaging issues using 95 RON long term. Even BMW 'recommend' the use of 95 here in the UK. It is our regular fuel, so available everywhere.

Typically our premium fuels in the UK, from top brand suppliers, have a better additive package, in addition to the higher octane values. This includes additives for carbon deposit control, cleaning detergents for keeping the fuel system and injection equipment parts in top condition.

Placing value on the benefits of the additives is harder to quantify. Unless we regularly are looking into engines, (running on different fuels), and witness the differences, there has to be a bit of trust that long term running and ownership benefits from their use.

[HighlandPete]

Originally Posted by Lobb

Don't forget it's different in the US. IIRC you have an average of RON and MON to get the rating of pump gas. I think you'll be using 93 pump gas as the equivalent of our 98RON.

Good point.

[drexplode]

I use Shell 93 only.

[bavarianride]

Originally Posted by Lobb

Don't forget it's different in the US. IIRC you have an average of RON and MON to get the rating of pump gas. I think you'll be using 93 pump gas as the equivalent of our 98RON.

CA pumps only have AKI 87 or 91. The US spec F30 fuel door says min. AKI 89, and recommended 91.

For my DD and occasional bursts to pass, 89(mixing half tanks of 87 and 91) and 91 yield same mpg and performance.

This article says RON 95 is similar to AKI 91.

https://www.ussportaircraft.com/docu...1_mean__3_.pdf

[bavarianride]

Originally Posted by HighlandPete

Good point.

Is RON 91 available in UK? That is the same as AKI 87.

At times local pumps had no AKI 91(RON 95), and the AKI 87(RON 91) seemed to work just fine, but at 10% drop in mpg(and reduced power level).

[anotheran]

Highest available non ethanol fuel - this I recommend.

[BEAR-AvHistory]

Its not worth buying cheap gas in the US to try to save a few hundred dollars a year

[TodmordenLad]

Thanks for your comments, guys, appreciated
So, 95 RON regular unleaded works ok, and BMW recommends it in the UK but 98/99 RON super unleaded gets the best out of the engine - which is why BMW uses it for their tests and official data
Hopefully my Shell loyalty card will soften the blow a little