Optimax or not

Bongo · October 4, 2004, 00:37

m http://driving.timesonline.co.uk/printF ... 20,00.html m

Anonymous · October 4, 2004, 01:34

Quote from: "MRMike"they do a dyno test which shows the fuel gives 1bhp over reg fuels, which to be honest is not a a bad gain per pound per fill up, esp at 20 p a gallon more.

does it say the dyno runs were done several times to get an average? or, that 1bhp extra is probably down to the dyno's error margin and not the cars performamce output.
If a car's ECU hasnt been tuned to take advantge of the higher quality fuels, i really cant see how optimax, BP ultimate ect.. can make a difference in a car's perfomance.

The only advantage Optimax will give our car is the extra additives that help keep the engine running nice and smoothly

MRMike · October 4, 2004, 14:03

Thanks for the link Paul! They didn't mention if the 1bhp was the result of dyno error, or outside that. I don't know about the premium fuels. I only buy them now because I can see how they would reduce pinking, as for performance gains? Not sure, esp not at WOT. If it cleans my engine it's worth the premium to me.

Anonymous · October 4, 2004, 14:21

I read this,

They did it on a single tank of petrol, its my understanding that it takes a time to work, If the ECU you adapt to your driving style then it can adapt to the petrol. The point is a) BP/Shell shouldn't say it has an instant effect or b) talk about 1.8L engines performing like 2.0L.

In America they have low octane fuels don't they rn 89/92 or something like that. yet spyderchatters post the same sort of performance as the Euro guys.

Having said that i've started to put optimax in if i can, my local garage does it for not that much more than regular. If its better for the engine, better for emissions, better for milage and possibly better for performance then why not.

aaronjb · October 4, 2004, 14:32

Quote from: "odub"If the ECU you adapt to your driving style then it can adapt to the petrol.

AFAIK the ECU in our cars isn't that clever, though.. The only way I can see an ECU adapting to petrol is via a knock sensor - and if it was dynamically altering the timing based on knock levels. If that was the case, it's theoretically possible that it would 'hear' less knock on Optimax, and you'd end up with a more advanced timing profile than on 97 or 95RON fuel.

QuoteIn America they have low octane fuels don't they rn 89/92 or something like that.

They have a different measurement of Octane, though.. So their 92RON is about the same as our 95RON (or is it 97RON, I forget) - effectively they are running the same fuel as us (though it may have slightly different additives due to emissions regs).

QuoteHaving said that i've started to put optimax in if i can, my local garage does it for not that much more than regular.

I used to run Optimax in the 300ZX, never had a problem, but can't say I noticed any improvements over SUL, however any changes, even over time, are probably too tiny for the butt-dyno..

I tried it in the Renault 19 a few times too, but found no difference.. The R5 GTT never got to try it - it always ran on SUL - but current club members do seem to run their cars on Optimax now whenever possible, and to date nobodies has expired due to it (that we can tell, anyhow)

Anonymous · October 4, 2004, 14:41

Ah i didn't know about American fuels being different.

If i remember the improvments are supposed to be related to the knock sensor in the way you say. But i guess it's never going to make that much difference. Maybe on a havily tuned car, don't the Japs use even higher rated stuff. Or race fuel at 102. Something like that.

aaronjb · October 4, 2004, 14:45

Quote from: "odub"Maybe on a havily tuned car, don't the Japs use even higher rated stuff. Or race fuel at 102. Something like that.

Yeah - my import 300ZX had a (ton!) of stickers inside the fuel filler door saying "Only fill with 100RON <fuel>" for about four different petrol companies.. AFAIK they use the same RON calculation that we do too..

You can get race fuel fairly easily in the states too (at some petrol stations as well!) which IIRC starts at 102RON (American RON remember!) and goes upward..

MRMike · October 4, 2004, 14:56

Don't different countries measure fuell differently though? America is ron/mon where we just quote MON values? Not sure about Japan

Anonymous · October 4, 2004, 15:35

Just reading up on this stuff.

For example Benzene, the well known cancer causing chemical added to petrol instead of lead? its the thing that damages cats and cats scrub them (when your engine reaches 400 degrees), So I guess that answers the importance of pre cats, and why they end up getting destroyed. Apparently its so dangerous that no motor should run unleaded without a cat, not even a lawn mower.

Well
Optimax has 3.3 (% Vol) and bp has 1.0 max (% Vol) normal unleaded is 2% apparently.

I'm going to stop reading there before I scare myself.

heathstimpson · October 4, 2004, 15:37

Quote from: "odub"Just reading up on this stuff.

For example Benzene, the well known cancer causing chemical added to petrol instead of lead? its the thing that damages cats and cats scrub them (when your engine reaches 400 degrees), So I guess that answers the importance of pre cats, and why they end up getting destroyed. Apparently its so dangerous that no motor should run unleaded without a cat, not even a lawn mower.

Well
Optimax has 3.3 (% Vol) and bp has 1.0 max (% Vol) normal unleaded is 2% apparently.

I'm going to stop reading there before I scare myself.

s:shock: :shock: s:shock: s:shock: :shock: s:shock: I'll have to get her to do the lawn from now on in

Slacey · October 4, 2004, 17:37

US measures octane in a combination of MON/RON, we use just RON. US 91 is equivalent to roughly UK 97 - I had to look all this up when the US turbo retailers asked about our fuel!

aaronjb · October 4, 2004, 17:41

Quote from: "Slacey"US measures octane in a combination of MON/RON, we use just RON. US 91 is equivalent to roughly UK 97 - I had to look all this up when the US turbo retailers asked about our fuel!

No surprise they can push silly power when they're running US 102 octane then - that must be like having 120RON over here (even accounting for those strange american horses they have.. s:lol: :lol: s:lol: )

Tem · October 5, 2004, 08:44

You can't convert between US-EU octanes s:? :? s:?
(without knowing both RON&MON octanes)

US gives the number as an average between RON and MON. Europe gives just the RON. Basically that sucks, cause RON pretty much only tells how the car idles or cruises without load. MON is what matters when you actually load the engine.

For example local 98 octane has 98 RON and 88 MON, which makes is 93 octane on US. Our 100 octane on the other hand has 100 RON and 96 MON, which makes it 98 in US.

And the 100 is helluva lot better than the 98 octane, though the difference on the pump label is only 2 octanes s:? :? s:?

Anonymous · October 5, 2004, 09:44

A while back EVO magazine did a long term test on optimax (although how long I can't remember, but it was over time and numerous fills).

What they found was that the performance improvement was negligible, but on stripping the engines down, the optimax fuelled engines was nice and clean whereas the other had lots of carbon deposits on the valves and other parts.

IIRC they concluded that it would probably improve the life of your engine and was worth it for that alone.

I'm still dubious given the old days when shell fuels was (unjustifiably?) known for causing problems with certain manufacturers engines. I always wonder the amount of pre-cat failures with and without optimax use. There is nothing to say that it might cause it, it's just one of those things that I wonder about (with no statistical evidence to back it up).

Found some details on the EVO tests here although it doesn't include the pictures which show the cleanliness/muckiness of the engine parts.

Anonymous · October 5, 2004, 12:46

m http://www.honestjohn.co.uk/forum/post/ ... =4&t=25851 m

The first post in the above link is interesting with respect to the Optimax cleaning-power claims.

Anonymous · October 7, 2004, 20:49

I ran my '02 Celi from new for over 5,000 miles exclusively on Optimax (with the exception of the first 1/4 provided with the car). Then after a severe rear end accident I decided I would get rid of the car and switched to normal Shell unleaded for a further 5,000 miles.

On the Optimax the tail pipe of the exhust was completely free of carbon deposits. Within a couple of tanks of normal Shell unleaded the exhaust had turned black with soot. s:o

s:o

Shell used to claim that Optimax is more highly refined than normal unleaded so that it includes less impurities and burns cleaner (can't find this claim on their web site anymore). My experience certainly seems to prove it burns cleaner. As for performance, it seemed more responsive on Optimax but I could never prove it.

My experience meant when I got my new '04 MR2, I decided to run it exclusively on Optimax again. And yes, my exhaust it spotless after 4,500 miles.... s:)

s:)

Anonymous · October 8, 2004, 03:02

Well i'll say it again, optimax in my tank after an extensive tune up and it made my engine knock on boost, NA you may make you think it's doing good, but i doubt it. s:evil: :evil: s:evil:

Slacey · October 8, 2004, 06:29

Quote from: "mr-s_turbo"Well i'll say it again, optimax in my tank after an extensive tune up and it made my engine knock on boost, NA you may make you think it's doing good, but i doubt it. s:evil: :evil: s:evil:

What do you use now then Ian, I thought the higher octane would stop knock (dependant on the system of course)?

Anonymous · October 8, 2004, 09:26

I thought the whole point of higher octance petrol was to stop detonation and therefore knocking.

What about all the highly tuned supras and such on race fuel.

Not doubting it, but its intresting to learn why.

I presume you had the ECU remapped for the new mods, could it be that the "knock timing/alteration" sub-routine (if there is one), was put out of kliter by the remap?

In other words, if you dyno'd and remapped the ECU when the car was full of optimax, would you still get knocks.

I know that higher octance fuel requires greater heat to release the greater amount of energy, so the compression ratio needs to be greater, to generate the required heat - question is, can the MR2 alter its compression ratio?

MRMike · October 8, 2004, 11:02

Quote from: "odub"I thought the whole point of higher octance petrol was to stop detonation and therefore knocking.

What about all the highly tuned supras and such on race fuel.

Not doubting it, but its intresting to learn why.

It is, Optimax is not 98 RON fuel though, It's only 98 RON equivalent, and then only when it leaves the refinery. It's only guarunteed at the pumps to be >91

Anonymous · October 8, 2004, 11:26

Really? I'm shocked.

Anonymous · October 8, 2004, 12:47

I've always used Esso superplus. This was what i had in the tank when i tuned it. Being in MK at the time, on the way home i put optimax in as that was the first petrol station i found. When i set off i could clearly hear a slight knock when boost came in. I simply took a bit of timing out at low psi and it stopped.

If i'd of tuned with optimax in, yes it would be fine, but something didn't like my switch of fuel. Maybe i just got a "bad" tank of fuel, i know you MK lot are tight, probably all the pumps are connected to the same supply and its watered down a bit!! s:wink: :wink: s:wink: s:D

s:D

Tem · October 8, 2004, 13:03

According to Japanese Performance Magazine, Shell Optimax is 98 octane in UK...

MRMike · October 8, 2004, 13:24

I thought that as well Tem, and while there are bits and pieces saying '98 RON' it doesn't say it at the pumps, or anywhere in the literature.

I posted about his a while back m http://www.mr2roc.co.uk/forum/viewtopic ... ht=optimax m

It's noticable that Shell have toned down there claims about Optimax of late, although they have never claimed during TV advirtisement that the fuel is 98 Ron. I feel this is partly due to the fact that the BACC is a lot more stringent with TV copy as opposed to print. Claims have to be legitimately substantiated before they get anywhere near TV. Although there are always clever sentence structure which bamboozle comsumers. IE "Dove anti ageing cream was tested on 10 women. 8 People noticed a difference" What that difference is could be anything. Same with the Optimax ad's largely unqualified statements.

"Shell Optimax. Designed for better responsiveness, just when it's needed" It's not even a claim, only that it's 'designed for better responsiveness'.

BP ultimate is a better fuel IMO, they state it is categorically 97 RON.

If you look at their own website I cant find anywhere where they mention it's 98 ron.

m http://www.shell.com/home/Framework?sit ... _1602.html m

Slacey · October 8, 2004, 17:18

Quote from: "MRMike"I thought that as well Tem, and while there are bits and pieces saying '98 RON' it doesn't say it at the pumps, or anywhere in the literature

My local Shell (Ketley) has '98 RON' on the actual pump head.. or at least they did - I'll make a point of checking next time I'm there.