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Optimax vs Ultimate


whimsical_chris
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Hi

When I picked up my A4 the chap said to use Optimax. I did.

But my little sister ( who like me isnt a fuel expert ) worked for BP for a while and said that the BP fuel ( http://subsites.bp.com/ultimate/uk/default.asp ) was a completly different fuel to their standard unleaded. She said that Shell ( http://www.shell.com/home/Framework?site...ut_ga_1602.html bit of a mouthfull isnt it...) add something to their standard to give it the extra punch ( ? ).

Any thoughts on which I should be using ? I dont have any connection or preference, but it would seem that maybe I should look at Ultimate.

C

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Its the octane rating thats the important part. Two fuels with the same rating will give the same performance. 98 RON is the highest rating you can get at the pumps, and most engines use whats called a knock sensor to listen out for the engine 'pinking' and advance the ignition as far as is possible right up to the point that pinking/knocking starts.

So if you put Sainsburys unleaded in (95RON) the ignition is adjusted to suit, and you'll lose BHP throughout the rev range accordingly.

If you run superunleaded (98RON) then the ignition will be advanced further as 98RON pinks/knocks at higher advance, and therefore the engine produces more power.

If you could get some Aviation fuel (100+RON) or add octane booster, I'm afraid you wont see any further increase in power. Std ECU's only work up to 98RON, and wont take advantage of even higher octane ratings. Thats where the specialist tuners come in, with their rolling roads etc. However, once setup for 100+ RON, you wouldn't be able to chuck unleaded in, as the engine would pink itself to death, resulting in melted valves, plugs, and worse still, holes in the tops of pistons.

So whereever possible, run SuperUnleaded, and make the most of the extra BHP.

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You can run what you like, but unless your ECU recognises higher octane rating than 98, its a waste of time.

Are you running a turbo? If so, the ECU may have been chipped to take advantage of the higher octane.

I could drive to Donington Park at lunch time, and fill mine up with Avgas from the pumps in the paddock. It would run, but I'd notice no difference in the performance. (apart from the drop in weight in the wallet department)

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No worries. Some engine tuners actually listen to the engine using a special microphone and bandpass system, so the operator wearing headphones can hear the pinking through the din of the transmission etc. At Dave Walkers (EMERALD) last year, when they rolling roaded my Fiesta, they used the system to monitor what was going on, and found the ignition was far too retarded. I've yet to go back to have her tuned properly. Just sourcing the bits for my race spec 2.1 at the moment, but once its built, I'll be back for a proper tune up, on Super Unleaded of course. 8)

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I think I heard somewhere that Avgas isnt too good for catalytic convertors, not sure on that though.

My point was why would Shell bother selling V Power if there is not benefit above 98 RON? They surely dont sell it just for the chipped market confused.gif

I dont have turbos, just the 4.2 V8 NA. I did look into turbos/supercharger for the A8 but due to compression ratios it cant really be done without major work frown.gif

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Theres little point in running higher than 98RON if your engine management system doesn't recognise it.

It could be that ECU's on later cars just use the knock sensor to allow any fuel to be used, regardless of the octane rating.

Or it could be a marketing ploy! Higher RON = Higher horsepower (but only if you drive an Aston Martin that supports higher RON etc). Watch who's filling up with it next time you see a pump. I bet its the BMW drivers wink.gif

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[ QUOTE ]

Its the octane rating thats the important part. Two fuels with the same rating will give the same performance.

[/ QUOTE ]

Not true!

Two fuels off the same RON (Research octane number) can performe totally different because the RON number is the ability to withstand pinking @ 600RPM with no load, this is no good for the real world so they carry out a test called MON (motor octane number) this is carried out 900RPM with a load (this is a real life figure). So two off the same RON numbers can have different MON numbers.

But then we go on about petrol pump rating, this is an average off the 2 figures, (often referred to as RON rating).

For performance engines it more interest to the owner to look at the MON.

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[ QUOTE ]

Theres little point in running higher than 98RON if your engine management system doesn't recognise it.

[/ QUOTE ]

Think you will find most German and Jap cars support high octane fuels because both them have over 100rating out the pumps at the petrol station.

Also Tony you shouldn't run unleaded in your car, If you check the petrol flap it should tell you min off 97 rating, that super or better all the time. 169144-ok.gif

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You also need to understand what additives are present in each fuel. Tobes is correct about the ROM/MON.

But there is also what extra goes in.

I've said this before (mate in the oil industry)

[ QUOTE ]

Although all the companies share facilities ie nearly all fuel in Southampton and a large surrounding area will come from Esso at Fawley each company puts in their own additives. In addition the super markets will go on the spot market at Rotterdam and pick up cargos of petrol whose origin could be anywhere in Europe or the Middle East so quality of base fuel will also vary. I’m sure 'company name' and the other majors will pick up the odd spot cargo but mostly it will be from UK refineries.

As a minimum try using branded petrol in one in 3 or 4 tanks

[/ QUOTE ]

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See, its really there just to create a stir, and fool people in to buying what they dont necessarily need.

Modified engines need higer RON so they can run higher compression ratios and more advance = more power. Your average motor on the street cant tell the difference between 98RON and higher, so its a waste of money. If the BP fuel is the same price, then give it a go, but prices do vary across the UK. Without a rolling road test on a std road car (german, jap or otherwise) then I really need to be convinced that its worth putting a higher RON than 98 in.

Show me a corrected rolling road graph, and I'll take notice.

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Back to the question, Shell has a rating off 98 and the BP has a rating off 97! Try find them ratings on there site smashfreakB.gif. for some reason they dont seem to provide them confused.gif

Becuase off this I have emailed both off them in the past and these were the figures they email back to me.

At the end off the day they are both about the same price and I dont think it will matter which one you use, Try them both and see which one you like best 169144-ok.gif

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[ QUOTE ]

Modified engines need higer RON

[/ QUOTE ]

Or stock engines that are pretty 'hot' to start with... wink.gif

The RS 6 owner's manual carries a warning that if 95 RON fuel is used, there is a risk of engine damage if full throttle or high engine speeds are used. I haven't noticed similar warning in the W12 manual, but it does say 98 should be used, with 95 acceptable with some reduction in performance.

Oh, and I just remembered, the A2 1.6 FSI recommends sulphur-free 98 RON petrol with cleaning additives too - FSI works far more efficiently if the inlets are clean and with higher octane fuel for the lean running when maintaining steady engine speed and load.

Additives make a big difference; as well as anti-knock, you want a 'clean' fuel that contains additives and has as few contaminants as possible, to prevent detonation. Having the fuel auto-ignite and try expanding before the spark fires and while the cylinder is still being compressed by other cylinders isn't going to an engine any good at all. A high octane fuel should also be designed to reduce the risk of detonation.

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You're right about some cars needing higher RONs though. I'm sure some Nissan Skyline and various Toyota turbos would benefit from a higher octane rating.

I used to run 11:1 CR in my 1030cc A-Series Mini, and had to pour a litre of Aldon Octane booster at every fill up. Man, that stuff smelt weird. I'm sure I'll pay the price later on in life. Without the booster, the engine used to eat Platinum tipped spark plugs on a good motorway run, and I certainly noticed the difference in performance then!

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[ QUOTE ]

See, its really there just to create a stir, and fool people in to buying what they dont necessarily need.

Modified engines need higer RON so they can run higher compression ratios and more advance = more power. Your average motor on the street cant tell the difference between 98RON and higher, so its a waste of money. If the BP fuel is the same price, then give it a go, but prices do vary across the UK. Without a rolling road test on a std road car (german, jap or otherwise) then I really need to be convinced that its worth putting a higher RON than 98 in.

Show me a corrected rolling road graph, and I'll take notice.

[/ QUOTE ]

Sorry forgot about this thread.

We have always run our high(er) performance cars on Optimax or Ultimate (optimax if I can get it)

My advice would be to always avoid supermarket petrol if you can - it is cheap for a reason.

I've run my Scooby on Optimax since it has been available and before that it was always premium-unleaded (not 95 unleaded). We ran the Audi (A4 Avant 2.8 V6 on it too) and we now also run the V70 on it. I would always put premium (optimax or Ultimate) fuel in any turbo car. Ideally Optimax.

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OK, I've had a tank of Ultimate in the car today, covered the best part of 200 miles in one run. After leaving the MK meet, the car was nowhere near as willing to move, as it is normally with Optimax.

Unfortunatley, had to put Esso slap.gif super unleaded in the car on the way back from MK, and it was bloody awful!!!!

Roll on tomorrow when I can put my Optimax back in laugh.gif

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[ QUOTE ]

OK, I've had a tank of Ultimate in the car today, covered the best part of 200 miles in one run. After leaving the MK meet, the car was nowhere near as willing to move, as it is normally with Optimax.

[/ QUOTE ]

Are you sure that wasn't anything to do with the massive burger you had Tony ? grin.gif

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