When I first bought my car, E36 328, I ran it on premium unleaded (usually Morrisons finest!). However after reading several comments on this website and listening to other owners I decided to switch to Shell Optimax. I have been using it now for two months and I have to say I have noticed absolutely no difference at all. The car certainly feels no faster and it doesn't get better fuel consumpsion (in fact it may even be a bit worse, although this could just be down to the colder weather).

Does anyone else use Optimax? Is there a better brand of super unleaded I could use? I am tempted to go back to normal unleaded since its cheaper.

Any thoughts or comments would be appreciated.

The owners handbook says that the engine can run on both and automatically adjusts depending on the octane rating of the fuel. It even says that if you run on 98Ron fuel you will get better fuel consumpsion.

i wonder why there is no proof of the car making better out of the higher rated fuel then ?

what bmw say is that the car will run on both,

what i say is that you will get no benifit on the current fuel map of the ecu.

Er...

Don't BMWs have knock sensors? if so they will compensate anyway.

I use Optimax on my Lexus and found after I reset the ECU it drove a lot better & give better mpg.

Will be using in the wifes Z3 after X-Mas

About 73 pence!

So not bad.

Its about 78-79p near me, I have just put some BP Ultimate in and there is no difference - so must be equivalent, I think it depends which is closer BP or Shell, there are 2 BPs within 4 miles and a Shell!

Nooo Paul, sorry I mean't that I have been using Optimax for the past 5 months and have just tried BP ultimate and found there isn't any difference so it must be the same in performance, but if I tried std UL it would probably be lower on performance.

I don't think there would be much difference between Opti and BP U as they claim the same points. But may stick to it for a while to see if there is a difference.

My car does run well and returns about 30mpg not bad for a 2.8 on a urban run in rush hour!!

Dave,

30mpg on a 2.8 mate? I'm currently getting about the same in an M3 Evo, and about 34mpg on a motorway. I suppose thats where you'll skin me in economical terms eh, on the motorway?

Dave,

when you say 30mpg is this what the computer tells you? my car reckons I get around 30-31mpg just driving to work and back but I also calculate fuel consumpsion when I fill up and that tells me I am getting more like 28-29mpg.

Sailorbaz, I would be truly amazed if an M3 actually manages 30mpg on an urban run!

Its an average, as driving urbanly it shows mid 20s and on the motorway about  34mpg @about 70mph.

The OBC isn't most accurate best to do calculations when filling up as Peter says.

On a Motorway trip to Luton at a bit above the speed limit  it returned 32mpg.

Peter,

Sorry mate, I was telling porkies! I was out tonight and decided to have a wee trip through the centre of Glasgow to see what I would get. After it starting off at about 14!!! it steadied to about 22mpg! Which I think you'll agree sounds about right?!?

And Dunc, yes I drive Miss Daisy! You're my passenger and I don't want to make you cry! ROFL

I think I have found out why I was finding shell optimax less than impressive.

After a long drive to London over christmas I filled up the car to drive home and worked out my fuel consumpsion on the way down to be 32mpg. This was great considering the trip took 10 hours, because of big problems on the M1, and 4 of these which were actually stationary in a traffic jam. When I got home I filled up from my usual petrol station and calculated an MPG for the return trip of 30. Strange considering that this time there were no hold ups and the journey was pretty my a constant 70 - 80mph.

The next time I filled up I just happened to stop at a different shell station to the one I normally use. Fuel consumpsion was better by about 2mpg than it normally is. I have alternated a few times between my usual petrol station and a different one and it is the same every time. The only thing I can think is that the pump at my ex regular petrol station is saying you are putting in more petrol than you actually are, hence making you think that the car is getting worse MPG. It's bad enough that I have to pay 80p a litre for the stuff without being charged for extra petrol that I am not actually getting! 

Anyway, much happier with optimax now and I can indead confirm that my car gets better mpg than with Premium UL.

I use "Any" branded Unleaded.  I avoid the Supermarket Petrol, even though it is "Branded", because it *does not have* the additives in it...that is one reason it is cheaper.  <Anorak mode> On the last 2,511 miles I have drank 474.89 litres, this returns 24.04 mpg.  (E34 2.0 litre).  Nowthen, as these special Unleadeds are approx 4p a litre more expensive.......that's about 5.5% more expensive.  Are you saying that I will improve my mpg to at least 25.32 on a permanent basis?

Also, don't forget the fact that ruins all personal studies / statistics.  If you try another fuel, you will probably drive a little different anyway, simply because you are experimenting.  A full and proper study would be about 6 months, to iron out any such circumstances.

Peter - did the fuel economy you calculated tally with the OBC to the same extent on both runs? Surely the other possibility is that your local station either has some dodgy stuff in its tank which makes the economy worse, and/or isn't giving you pure Optimax even when it says it is.

Ian

Ian,

No, the OBC gives the same or very similar for both my local petrol station and the one I am now using. The difference between the OBC and the actual consumption when using my local shell station averaged out at about 3.5mpg. Now I have changed to a different petrol station it is about 2mpg.

Paul,

I understand what you are saying about the cost versus improvement in mpg and it probably works out six and two threes on a pence per mile basis. You are also right when you say that I have not done a full and proper study, although I do have 4 months worth of data and I am still collecting. My Girlfriend thinks I'm obsessed! She says if I don't stop soon shell have the men in white coats take me away  

When these men in White Coats turn up, don't worry, it's the BMW lab technicians, coming for your data.

"We have come for your data"  which is a b*st*rdisation of a musical cult film of the 1970's...oh, I'm wandering.

Now, if you swap back to ordinary punters unleaded, do you reckon your mpg would be significantly lower...that is the question.  6 months of each study please...publish results on here.

Right.

4 tankfulls of this have now been drunk by my old gal.

MPG?  Naff all difference whatsoever, on "To work and back" or long runs.

Also, after a 7 hour run from Torquay to Preston on Friday last, I left the car on Saturday,  Sunday, I had a "No start situation".  In my impatience I pressed the accelorator pedal, and the smell of fumes told me I'd wet my sparky world, so I took out the plugs to dry them.  These plugs are NGK, and are 2 months old.....Plugs 2,4, and 6 were coked up to hell!  This is an indication of Valve guides knacked, but the coincidence with my Optimax experiment...just coincidence?  In the end, I had to give the car an Oil Start, because I'd rinsed the cylinders with petrol.  The neighbourhood was pleased to have a cloud of burning oil at 10am Sunday morning!!!!

All spelling mistakes are Copywright protection!

I would be supprised if the coked up plugs is connected to using optimax, although I could be wrong, it has been known! Also I thought that coked up plugs was an indiction of the car running rich. Does you engine need adjusting before it can run on 97Ron fuel, or does it have a knock sensor?

Appart from fuel consumpsion how did the car run?

OK.  Engine Adjustment.....I thought that my 1989 520i was "Set up" (At ECU level) to run on the higher octane stuff in the first place, so ordinary unleaded was too low R.o.n???

Also, if it was a mixture problem, all 6 bangers would be in same condition.  Only 3 were coked. Pots 2,4, and 6 if that is any help to anybody.

I do not know if my engine has a knock sensor.  Help please forum?

Coked up with crusty deposits, removable only by a small screwdriver, is a sign of Valve guide wear.  Even the pictures in the back of the <spit> Haynes manuals have that bit correct.  I put 6 newuns in, Champion brand this time. (NGK before)

Running.  Well, immediately, the warm tickover went up to 730 (Visual guess from dashboard dial) from about 690/700 when on ordinary unleaded.  690/700 is too low according to the books, 730 is within spec, so that made me think I was onto a winner.  Other than that, I cannot say that  I noticed any difference whatsoever, for my kind of fully legal driving. (OK, 80-85 on motorways when it's safe).  Track day attendees may say they notice a difference.  I say it has cost me £4.00 per tankful extra, for no apparent reason.  I'm knocking it on the head as from tonights fill-up unless this forum can pursuade me not to.

I wouldn't have said that it was set up to run on 97ron fuel, more that the engine should recognise what octane rating the fuel is and adjust itself according. This way when you put higher octane fuel in it adjusts the ignition timing so that you see the benefit, ie more power. The engine does this using a knock sensor. If you car has one then it should run on any any octane fuel without adjustment. However not all cars have a knock sensor.

If you are not noticing any dfference then there is no point in putting it in, although I could argue that it will in fact be cleaning your engine, removing carbon deposits from the valves etc. EVO magazine did a test where they ran three cars on normal unleaded then switched to optimax. In all cases the cars accellerated quicker using the optimax, although the differences where only small. They also looked inside the combustion chamber using an endoscope and the optimax did clean off cruddy deposits. This could be why you are now seeing the symtoms of valve guide wear. Before carbon deposits might have been helping to make the seals and now the optimax has removed the carbon the worn guides have started to show up. Just a thought.

Aye, I've got that Evo mag Pdf'd somewhere.  They did use recent cars too, not lovely old shapes like mine <g>

And, their acceleration testing is probably far greater than normal road use, I don't want throwing back in my seat, on 95 or 98 R.o.n!!

As for fuel cleaning, I used to put a glug of injector cleaner in every 10 tank-fills or so.

I'm going back to 95, to keep my car alive, to keep my guides from crustin, and stop my wallet bustin, this old shape is gonna last, till the tax man he gone past, 10 long years to go, will it make it----I don't know.

Sorry, rap mode OFF.