2009 Z4 3.0 30i : which fuel grade?

Bluebottle

Bluebottle

Member
 Plymouth
Quick question, I have run all my 2.5 E39s and Saab 9000Aero ( as well as my old Cortina) on Momentum /Shell 99 octane.
The handbook for my Z4 suggests 95 octane ; I will continue with 99 unless anyone can tell me why I should not.

Cheers.
 
Bluebottle said:
Quick question, I have run all my 2.5 E39s and Saab 9000Aero ( as well as my old Cortina) on Momentum /Shell 99 octane.
The handbook for my Z4 suggests 95 octane ; I will continue with 99 unless anyone can tell me why I should not.

Cheers.
Click to expand...

Cos it's a waste of money? It's your money, though.
It's an old N52 engine not a 600bhp highly-tuned Lambo. :D
 
The engine can’t exploit the higher octane …it’s not that clever / capable….however most of these fuels have a higher content of detergent additives…they will certainly help clean the injectors, combustion chambers etc..

So no harm, some benefits…if you’re happy I’m happy :thumbsup:
 
I've had 4 BMWs with the N52 engine, two E86s, an E91 and currently an E90, and BMW recommended a minimum of 98RON whenever possible. So I've always used 99RON in them "whenever possible"!

But apparently the N52s in E89s can be run on 95RON. Despite that I'd probably stick to the better stuff because it has less Ethanol in it which is hateful stuff, especially if the car doesn't get used too often. And for the reasons B21 has mentioned.
 
My 23i manual says minimum 93Ron.
I usually run on cheaper supermarket super unleaded, feels slightly better.
Wouldn't bother with 99.
Apparently higher octanes are slower burning fuels, so you can enjoy more pops from the exhaust.
I know my motorbike wasn't keen on super, just felt rougher and more vibration through handlebars.
 
Bluebottle said:
Thanks all.
Can this car be "tuned" by electronics to optimise it for 99RON?
Click to expand...

Not really…main benefit of octane is to increase the amount of ignition timing and/ or boost level in a turbo..in a NA the ignition timing is probably as advanced as needed….you MAY get 1-3 BHP more ….on a turbo each increase in octane if tuned gives about 5-10 BHP per litre displacement
 
Thanks folks, very interesting. I like the thought of using the best fuel, I have never searched out the cheapest fuel in fort years of driving, just the most convenient filling station.

I take on board what you are all saying and will try a half tank of various fuels to judge for myself whether I can tell the difference.
Shell V power, Tesco Momentum, Shell Regular, Tesco regular, and Esso.

I may report back......
 
You may not notice any difference between 95 and 99 in your car as it was built to run on 95 RON, but you might get slightly better economy on higher octane fuel. If nothing else it might be an interesting experiment!

All my N52s (and M) specified at least 98 whenever possible, so I imagine the ECU would adjust the ignition timing if I put 95 in the tank. Until a couple of years ago my nearest filling station was a Tesco so I always used Momentum. It was also cheap as Momentum is only 7p a litre dearer than Regular at Tesco, whereas it's more like 15/20p difference at Shell or Esso. :o

FWIW Premium fuel at BP and Jet is only 97 RON so I try to avoid those!
 
You could use 100 octane aviation avgas, but danger there was burning the valves out. Plus the lead.
Could be danger using too high RON fuel thinking it's better.

Don't know if garages still run summer and winter blends.
 
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