Why not use premium. THis topic pops up from time to time, and I don't get it. IF you love your car, why not use the best. Maybe it helps, maybe it doesn't, but it's peace of mind nonetheless IMHO. Oh yeah, us hillbillies down here in the sticks don't have 94.
Have a chip so I have to use it and I can't get any higher unless I drive 35 minutes to the otehr side of the city.
I used to use 89 because i always thought premium is just too expensive but when you think about it you are spending an extra $1 or $2 for premium that is really not that big of a deal. I switched to premium a littlw while before i put in the chip and i noticed a difference in my car. I used the injector cleaner too. My car was a bit more responsive and peppier and just ran smoother. This is on a car that doesn't have really high miles either 80k.
You American's are just too damned lucky! Over here in the good old UK we have either 95 RON standard unleaded @ 83p per litre, or 97 RON "ultra" unleaded fuels.
BMW's running on a standard ECU will benefit a little from the higher RON fuels. Those running a lot of modifications or ECU upgrades/standalone ECUs will obviously benefit if not require the higher RON fuel. If you have any form of forced induction then the higher the RON fuel you can get the better as this will reduce the chances of detonation (which is even more dangerous to your engine with forced induction providing positive pressure into the inlet manifold).
I used to drive RX7s prior to the BMW (needed a more "sensible" car) and there are many many issues with fuel types regarding rotory engines. The general rule is the higher the RON rating the better as this reduces the risk of detonation and hence engine death. However the cost rockets as the RON rating increases. For example 95 RON is the standard consumer fuel over here which is pretty much identical from all suppliers and is (still over priced) 83.9p per litre. 110 RON race fuel is around £8 a litre and 112 RON race fuel is around £11 a litre.
Also don't forget to add into the equation that different fuel suppliers use different additives in their fuels. For example here in the UK, BP supply BP Ultimate fuel which contains quite hight levels of tolurene (good for cleaning engines and burns clean) but lower leves of other detergents thant Shell Optimax fuels which contain a lot more detergents and are known to sometimes leave a residue in the combustion chambers wich over a long time can cause engine damage. Having said that of course the Shell Optimax is 98 RON which is the highest easily available fuel RON in the UK. I personally use 95 RON in my e36 most of the time as the difference is negligable for normal driving. However for heavier use I go straight to the BP Ultimate 97 RON as I perfer the higher RON to reduce the risk of detonation and the combination of fuel aditivies that burn cleaner and reduce risk to the engine.
There are a lot of interesting threads relating to fuel types, RON and Octane ratings over at www.teamfc3s.org/forum
I run 93, except the last fillup (gas prices are getting waay expensive) I tried the 89, dunno if it was just me (perhaps going from 30degree days to 50degree weather) but I could of sworn I felt of loss of power.....
Theorically the higher octane will decrease the chance engine denotion at higher temps/rpm so your ECU will not retard timing (loss power.) Pretty much everyone I ever spoke about this always said they never noticed a difference between 87 & 93/4 going from cars whoms recommended octane was 87. So I don't know how much truth there is to this theory.
Gonna run 93 again next as see if Im just going crazy.
To do list:
UUC System U TDM- 3/05
M50 manifold converstion 3/05
off to the tuning shop for custom software 4/05
Cams/lightened flywheel, throttlebody........ well lets see what happens
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