just put 95 ron in, problems...

domsz4 said:
If you saw the crazy s**t some of the labs do with o2 sensors a bit odd odd fuel isn't going to screw them. More than likely they were on their way out and the larger than normal change just finished them off.

It's true that a car turned for 98 will run worse on 95 but the z4 is not running on some simple ecu. I'd be surprised if it didn't have a closed loop system to cope with changes in fuel. Hence the total bull s**t that as soon as you put 98 in its faster
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Change in fuel grade doesn't screw them, but it can be enough to cause the EML light to come on within a short distance referencing the O2 sensors. I have reset both mine and Taz's and neither have come back on afterwards.
 
Update on this

Since cleaning and swapping round the vanos solenoids I had a spell of rough running and the emissions light came on. Had a p1554 code stored which I've narrowed down to the exhaust solenoid so putting a new one in tomorrow and hopefully no more problems...
 
new solenoid in and running much better. It's noticeably smoother, quieter and I've actually got some torque in the lower range.
Did notice though that the oil in this area of the engine is really dirty despite an oil change less than 500 miles ago so not sure why that would be unless it's just not circulating properly?
 
SeanConnor said:
Daily Mail science I'm afraid JimBob78. There is no way you would be able to detect the difference between 95 /97/ or 99 RON fuel with a modern EMU and on only one tank. As for failing sensors .. bollocks this is what is called auto-correlation or mere coincidence. The higher rated fuels tend to have better additives which ARE beneficial but only after several tanks of the poor stuff. Source ? My chief engineer's wife who is a Ph.D fuel specialist with BP :-)
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"Bollocks" to it being a mere coincidence.
If it was,it wouldn't happen to several owners when using standard fuel.
It can't be coincidence that it has happened to several owners on this forum over the years,and as others have said, a reset of the fault codes appears to stop the o2 sensor fault s re appearing,but with mine it didn't, and needed new o2 sensors,IMMEDIATELY after putting in 95 Ron unleaded,as it was running like crap,so I could tell an immediate difference!
Source,actual owners experience's, Inc my own.
 
nfbr said:
SonnyA85 said:
Again that is a myth I cannot believe people still believe.

Cars have fuel filters. What is the purpose of the filter if it allows dirt and stuff to get into the engine?

I'm also betting refineries have filters as do petrol stations, etc. I'm just guessing here but you would think that they would do to stop issues should something get in there that shouldn't.

I think all performance cars are designed to run on 95 minimum. However it should tell you in the manual if you have a look for the exact spec that should be used. Would be interesting to see what it says in the M manual. Basically the car shouldn't have any issues with 95, it will still work 100% fine. It will however run with a bit more power and refinement on the better grade stuff.

I've used a tank of BP Ultimate and £20 of performance fuel from a non major branded station. The car ran the exact same on all 3 IMO.
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Not necessarily true. 2.5si and 3.0si owners should be fully aware that their car does not have a fuel filter.
It has a basic mesh strainer built into the fuel pump, but no replaceable / serviceable fuel filter.

If a car's mapping has been done so that it requires 98 RON fuel to run its best, then ideally that's what you should run. Of course you can put 95RON in there, I may run a little odd for a half mile or so, but by the time you get to that point the ECU will have had readings from the knock sensor requesting it to slightly retard the timing to keep the engine running safely.

The safety systems within your ECU are very very quick to take things away in order to keep your engine safe, but very slow to put them back.

So when you hear of people feeling a huge difference as soon as they start to run 98RON fuel, that's total bull... It'd take at least a quarter tank of the stuff before the ECU would be allowing the timing / ignition to be back in a position where it will give the optimum "requested variables". I very much doubt anyone would really be able to "feel" the difference anyway.

It'd be like asking someone to see the difference between 250ml of water and 251ml of water.
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+1

Best explanation here :thumbsup:

If the car is mapped for a higher octane fuel putting anything lower than that will cause some drop in performance, obviously if its mapped for 99 and you put 98 in its not going to be a massive difference but if its mapped for 99 and you put 95 in the car will suffer (this would likely cause knocking on high performance engines) but this is all very variable!
A bog standard Z4 should run fine on 95/98/99, as mentioned before there will be increased performance on 99 but this will be all but unnoticeable.

As for the Z4M, it is a higher performance engine and is more likely to notice a sudden chance in octane but again the engine has a knock sensor and a clever ECU which should adapt, will the car run like it did on 98? No, but it wont grenade either.

My own personal opinion would be:
Z4 - 95RON+
Z4M - 98RON+
 
if a car capable of taking advantage of higher RON, I don't understand why you wouldn't put in all the time for the sake of a couple of quid, then you just know it's running at it's optimum.
 
I'll need to check my petrol cap next time I fill up. I'm sure it says 91-99 RON on it. It's a 3.0.

Tesco do a 99 RON wonder if it's worth buying or stick with BP and Shell (Ultimate and V Power Nitro).
 
Treat your car like you would your own body ie why drink crap like 'Doombar' when you can get something decent like 'Old peculiar'. Its all beer but there is a difference......
 
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