Petrol confusion!
Discussion
I have to confess I am not totally clued up on petrol types. I have currently got a 1995 Lancia Delta that has apparently always taken 95. Whilst at a Shell garage in Hungary the petrol pump attendant (yup..they still have them over here 
) tried to put Shell V-Power Racing 99 in it. Told him not to as I had no idea what it would do to the engine + I don't understand Hungarian 
Can someone please tell me what if any difference there is. Cheers, Ministry
) tried to put Shell V-Power Racing 99 in it. Told him not to as I had no idea what it would do to the engine + I don't understand Hungarian Can someone please tell me what if any difference there is. Cheers, Ministry
All I know is the higher the octane rating (98/99 etc) the more power it has, so the car should perform better. Not heard any adverse effects though. Everyone seems to rave about optimax though. Only other thing I've heard is to steer clear from always using supermarket fuel as it's a lower grade.
IIRC you can upgrade your fuel type with no changes required, but if you want to downgrade, then you need to get the ignition timing altered so suit the new fuel. All depends on how often you can get the "racing" fuel. If its gonna be regular, then change the timing, if not, go with the 95RON settings and accept the improved performance (although not optimised).
As long as you stay with unleaded, you'll be OK..
As long as you stay with unleaded, you'll be OK..
quote:
All I know is the higher the octane rating (98/99 etc) the more power it has....
Not STRICTLY true... what it does affect is the way the fuel burns, so it leads to an increase in power from the engine as the combustion is better as it burns more cleanly.
quote:
Only other thing I've heard is to steer clear from always using supermarket fuel as it's a lower grade.
Common misconception... everyone buys fuel off eachother - so basically it's all the same stuff, it's just that some put in additives before the point of sale.
As for OptiMax, check out the review in the current EVO magazine... or do a search for the Shell site.
I've just used a tankful of Optimax in my 3k old Civic Type R with the following results.
Cost of Optimax 78.9p/litre
Cost of Shell U/L 71.9p/litre
Fuel consumption over it's life so far has been between 24 & 32mpg, averaging 27mpg & on this tank did 26mpg, so fuel consumption doesn't really change.
Performance-wise, it did run really smoothly, but then again it always does. I noticed no change in performance at all.
It is supposed to keep my engine clean.
Shouldn't normal Shell do this anyway?
Worth 7p a litre more?
Based on this tankfull.
Is it bollox!
Does anyone else have any views?
Cost of Optimax 78.9p/litre
Cost of Shell U/L 71.9p/litre
Fuel consumption over it's life so far has been between 24 & 32mpg, averaging 27mpg & on this tank did 26mpg, so fuel consumption doesn't really change.
Performance-wise, it did run really smoothly, but then again it always does. I noticed no change in performance at all.
It is supposed to keep my engine clean.
Shouldn't normal Shell do this anyway?
Worth 7p a litre more?
Based on this tankfull.
Is it bollox!
Does anyone else have any views?
My twopence worth
Based on an M3 E46
Tesco unleaded fuel 200 miles from the tank
Shell Optimax 300 miles
Same road, same driving style, no major differnce in temp
Car was and is definitely beter on the optimax
Its smoother and more rev happy nad wants to play for a bit longer
Definitely worth the money
Based on an M3 E46
Tesco unleaded fuel 200 miles from the tank
Shell Optimax 300 miles
Same road, same driving style, no major differnce in temp
Car was and is definitely beter on the optimax
Its smoother and more rev happy nad wants to play for a bit longer
Definitely worth the money
My experience with OptiMax has been pretty good too...
Audi S3 loves it... as do all the Ford's I've driven at work with it in the tank - noticeably the ST170 and the Puma. Even the misses Smart seemed happier...
I'd give it a tank or two, keep an eye on the cost / mpg / performance and make your own mind up.
Audi S3 loves it... as do all the Ford's I've driven at work with it in the tank - noticeably the ST170 and the Puma. Even the misses Smart seemed happier...
I'd give it a tank or two, keep an eye on the cost / mpg / performance and make your own mind up.
This was covered in an earlier thread.
Optimax (98.4 RON) can give you more power but only if your car's ECU can recognise its there and advance the timing accordingly. Most cars don't do this (they just retard when they detect pinking and are set to run with 95 RON U/L) but some performance cars may have this feature.
My Golf always runs on Optimax and the timing is manually advanced accordingly - with 95 U/L it pinks like crazy past 4K.
Optimax (98.4 RON) can give you more power but only if your car's ECU can recognise its there and advance the timing accordingly. Most cars don't do this (they just retard when they detect pinking and are set to run with 95 RON U/L) but some performance cars may have this feature.
My Golf always runs on Optimax and the timing is manually advanced accordingly - with 95 U/L it pinks like crazy past 4K.
I think (but I could be wrong)it all depends on how clever your engine management is. The higher the octane rating the less prone to detonation the fuel is, so your engine can run with more ignition advance. If your engine management uses knock sensors and stuff to dynamically advance the ignition as far as it safely can then it should run better with the higher grade fuel. Some cars need a manual reset in order to relearn the settings required for the new fuel. If you haven't got an adaptive management system I don't think you'll notice much of a difference.
spnracing beat me to it, need to type faster.
>> Edited by Basil Brush on Thursday 27th June 15:57
spnracing beat me to it, need to type faster.
>> Edited by Basil Brush on Thursday 27th June 15:57
Peritas I have slightly differing results.
Again based upon E46 M3
Std U/L 280-300 miles/tank
Super U/L 280-300 miles/tank
Optimax 280-300 miles tank.
Same road/conditions/driver etc.
However, Std U/L, under load (3rd gear, low revs, large throttle opening) engine will get close to pinking.
Not so much with Super U/L
None with Optimax
I prefer Optimax but no benefit in fuel consumption
Again based upon E46 M3
Std U/L 280-300 miles/tank
Super U/L 280-300 miles/tank
Optimax 280-300 miles tank.
Same road/conditions/driver etc.
However, Std U/L, under load (3rd gear, low revs, large throttle opening) engine will get close to pinking.
Not so much with Super U/L
None with Optimax
I prefer Optimax but no benefit in fuel consumption
CJN,
The CTR does have a knock sensor and will adapt to the Optimax octane level. Looking at an article Evo did, it did seem to increase mid range acceleration times and helped clean up the valves quite nicely.
One thing they did mention was that the effect of the Optimax fuel could still be noticed even after a couple of fills of regular unleaded. So putting in a tank of Optimax once every few fill ups should still have a beneficial effect and would certainly prove to be less costly.
The CTR does have a knock sensor and will adapt to the Optimax octane level. Looking at an article Evo did, it did seem to increase mid range acceleration times and helped clean up the valves quite nicely.
One thing they did mention was that the effect of the Optimax fuel could still be noticed even after a couple of fills of regular unleaded. So putting in a tank of Optimax once every few fill ups should still have a beneficial effect and would certainly prove to be less costly.
Another thing with octane ratings is the way it detonates. A low octane fuel may pre-detonate if used in a high compression engine. My Type R Accord used to hate 95 even though it had a clever ECU. It was OK on 97 but could be made to 'pink' if nailed in a high gear at low revs. If memory serves me correct the hand book recommended a minimum of 98 ..... Which of course was then discontinued.
>> Edited by ultimapaul on Thursday 27th June 20:52
>> Edited by ultimapaul on Thursday 27th June 20:52
quote:
Optimax (98.4 RON) can give you more power but only if your car's ECU can recognise its there and advance the timing accordingly.
How can you actually tell whether the car's ECU recognises that there is a different fuel in it's system? Is there anything specific that you can look for?
One thing that was very noticable on a Cerb with sports pipes was that the quantity of overrun decreased dramatically with Optimax. I can only assume this is due to a better burn that with super unleaded.
Runs smoother and 'bogs' down less but hard to quantify amy performance improvement.
Runs smoother and 'bogs' down less but hard to quantify amy performance improvement.
quote:
How can you actually tell whether the car's ECU recognises that there is a different fuel in it's system? Is there anything specific that you can look for?
You could probably check on net or speak to dealer. I gather some cars can take a while to adapt, such as Scooby Imprezzas(?), and a manual reset can speed the process up.
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