After using Optimax in my MY02 Sti (type UK) for over 12 months, I decided to have a change and tried Esso Supreme - and I am very very surprised at the difference.

The car pulls noticably better at lower revs and pulls harder at higher revs in all gears - to be honest I had forgotten what performance the car really had (I thought I had just got used to it)

I find this hard to explain and have no scientific proof - other than what it feels like to me - but the improvement is very noticable. I am still checking the mpg - but given that I can use a higher gear a lot of the time (town driving), I am hoping for a small improvement.

Any ideas, comments or suggestions of other fuels to try ?

Scoobsti.

 

If you get on well with it in your car stick with Esso.

However, unless things have changed in the last few weeks Optimax and Q8 SUL ( in Cambridgeshire at least ) are the only fuels which have a 98 ron rating.

 

I thought that but no-one ever believed me.

 

I have been using Sainsburys super unleaded for the last 3 weeks or so. The car seems smoother on it than it did on Optimax. Also(and this is worrying) I notice a strange diesel type smell when using Optimax, not just the once but quite often.

Hmmmm.

 

Eeeek, could the station have swapped tanks or something!! I always use optimax and find that the car seems very happy on it. If I couldn't find any, I'd use shell SUL, which seems highly regarded.

Does anyone notice any more knock link activity with Esso? Most people with KL's say that optimax is best in terms of KL activity, with BP Ultimate producing quite a lot of unwanted activity. Haven't heard many comments about Esso in this regard.

NS04

 

Interestingly really when you think how so many people get differing results with fuels. The one fuel I have never felt a benefit from is Optimax and yet I have never had a bad experience with Ultimate from a performance and economy perspective, even when I haven't used the 5 tanks full that it says you need to use before you can tell a difference.

 

My experience based purely on knocklink activity.

1) BP Ultimate - most k/l activity
2) Esso/Supermarket SUL less k/l activity than 1
3) Optimax - less than both the above so assume is the safest for my car.

 

Mine seems to be running quite happily on optimax - 315bhp and 310lb/ft

 

My car is noticeably faster on Esso too (MY99 RB5 WR Sport)
and is what i use as a preference after trying both Esso and Optimax.

 

It isn't that as I use different Shell garages at different times, theres 3 in my area that I use depending on mood and if I cba.

It really is strange, Sainsburys SUL just seems.....purer somehow.

Having said that I filled with Optimax today as that was easier than going Sainsburys on a Saturday.

 

Mine seems to run much better on Optimax, if on any rare occasion i cant find shell and have to fill up anywhere else the cars seems more sluggish and does not run as smooth at low revs around town.

 

sainsburys super is bp ultimate, theyre the same company

 

Mine is ace on the good old optimax....320bhp/320lbsft can't be too bad

 

My car is also noticably faster on ESSO.

 

I also find that Esso appears to be a better quality of fuel compared with Shell 'Optimism' I have noticed less activity on the KL aswell (not that i had much anyway) I use Optimax whenever i cant find a Esso garage

 

how can a car be faster on 97 ron rather than on optimax 98 ron? apart from the fact that imports need booster to 100 ron regardless unless the ecu has been modified to take 97 ron super unleaded and uk subaru's run on 97 ron super unleaded anyway you shouldnt really see a difference because the ecu isnt programmed for the extra ron.having said that my friends integra type r seems quicker on 98ron but they are all different and it may be a mental thing too. if esso was proven better than optimax i still wouldnt use shell becasue i would need more booster at £13 per bottle

 

I don't think that every tank of optimax is bang on 98.

 

For the last couple of weeks I've reverted from Esso SUL to Optimax. As a result my scoob has become sluggish. Doesn't pull anywhere near as hard as it did with Esso fuel.

 

Is PPP mapped for normal SU ? In which case should it run better on 97 Ron than 98 Ron ?

Confused

 

Its not they say 98 is a minimum and can be upto 98.6

 

if thought optimax started off at 98ron then degraded downwards over time.

 

all petrol degrades but takes months/years

 

Is it not true that a leaner mix produces more power, but with greater risk of det. Perhaps the lower octane rating 'feels' better as it brings the car closer to the border of increase performance/increased det, but at a risk.

Or am I talking cr@p?

 

As I understand it, Esso UF has a higher calorific value then Optimax, so for the same timing will produce more power. Optimax is higher octane though, so will allow the engine to run leaner. Or something like that. Or I might be talking rubbish...


M

 

Hi,

the read the RON rating as 'Knock' rating - they higher the RON value the less chance your engine will be likely to knock (commonly known as detonate) - this is especially the case if your engine has been mapped towards a high RON rating (such as 97/98).

As mentioned in the post above ESSO SUL does indeed have a higher calorific value per unit than Shell Optimax - however Optimax does include some rather nifty cleaning agents that are a huge benefit to your engine but that does not mean you have to fill up every time with Optimax, maybe once every 3-4 tankfuls of ESSO Sul?

As far as I know the order is Esso SUL, BP Ultimate and then Shell Optimax. I wouldnt use Texaco SUL as it contains very little cleaning additives and the calorific value (or 'burn' as people call it) to be quite honest - sucks.

As for Sainsbury SUL and BP Ultimate, I think the additive combination is completely different so you dont gain the benefits of BP Ultimate when using Sainsbury SUL (ie the RON (stated to be 97) or cleaning ability). Rule of thumb is to avoid Supermarket fuels as they tend to be raw fuel with very little additives ( = bad for your engine).

Hope this helps

Mark

 

Any petro chemical chemists or graduates here that could do an analysis ????

We once had a customer who did an analysis on oils in cars and proved to us beyond a shadow of a doubt that ester based oils are better

He did it in his final year of his degree

Mike
Camskill

 

I read somewhere that Esso has a higher MON rating that Optimax and it's MON not RON that is the more relevent figure on a turbo car in terms of the fuel's resistance to det?, does anyone know if this is true?.

No Shell stations round here anyway so always Esso for me

 

Mon is exactly the same test as RON bar for 1/2 small differences (tested at a lower/higher RPM?). Hopefully someone can confirm?

 

Nice to know I'm not alone in thinking Esso suits my car better !

I thought it might have something to do with my Scoob being a Type UK and maybe being set more for 'normal' fuel than Optimax - although I admit I can't see how this would work - but there again I'm not a fuel scientist and this is a complex subject.

My other theory is the old one of the performance additives in Optimax degrading quite quickly. IIRC the one of the additives is Toluene (the last T of TNT) which can lose it's effectiveness over time (weeks or months, not years)

Scoobsti

 

there was a huge discussion over on cliosport about this and someone actually had the sense to ask the driver filling up at sainsburys as he noticed it was a BP lorry. the driver said yep its all the same stuff. thats how i know. so guess its true?