Does anyone use super unleaded when their car runs on normal unleaded, for extra performance? My Honda dealer suggested Shell Optimax for my Civic Type-R, if the price differential is relatively small, as it is 98 Ron as opposed to other super unleaded which is 97 Ron.
Has anyone noticed the difference? Is Shell really better than the others? Is it worth the extra 4-5 pence per litre? Does it have any long term effect on the car?
Based on 12,000 miles per year, I calculate it would cost an extra £100 per year. So if there really is a performance difference it could be worth it.
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At these octane numbers, the increase in performance or economy is roughly proportional to the increase in octane number, IF the car has a management system which adjusts for fuel quality. So a change from 97 RON to 98 RON will give a 1% improvement in economy, which is worth about 0.8p/litre. Since the price differential is invariably much more than this, there is no economic benefit in using higher octane fuel. Performance increase might amount to 0.1 sec reduction in 0-60 time and a 0.5mph increase in top speed, but except with very accurate timing equipment you wouldn't be able to measure any performance improvement.
If you just want to feel good, then go ahead and pay extra for higher octane fuel.
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I was wondering about this Optimax stuff, so while I was down on merseyside last weekend, where premium fuel like this costs about the same as regular unleaded does here in West Cumbria, I filled up with Optimax. My gauge was in the red before and I left with a full tank.
I could detect no improvement in the way my 2.5 Omega drove. I do the trip quite often so know pretty accurately what the trip computer will show on the return journey - usually 32 or nudging 33 to the gallon as I leave the M6 at Penrith. This time it was 32.6 with the Optimax.
So no noticeable performance improvement and certainly no gain in fuel economy - I won't be spending the extra in future.
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On the other hand, if the engine (Honda 2 litre) is designed to run on 100 Ron octane then running on lower octane fuel means the ignition will always be retarded. Not a good idea, surely? For maximum efficiency and for he avoidance of detonation, the highest octane fuel available would seem a sensible option. After all its a high powered engine running up to 8000rpm. Shell claim other benefits beyond the 98.6 Ron rating, such as cleaning the combustion chamber. I'd be inclined to adopt the dealers advice, in this case.
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The car is designed to run on normal unleaded - the dealer just suggested that some people had noticed a performance improvement by using Optimax. Perhaps he's just friendly with the local Shell man.....
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Generally speaking, an increase in octane number means a decrease in calorific value. Unless the engine is designed to take advantage of increased Octane by advancing the ignition, or is designed so that higher octane is required to protect the engine from knocking, there will be no benefit *DERIVED FROM THE INCREASED OCTANE* there may be other benefits which are complimentary though.
Lower calorific means lower energy, so less mpg and less performance.
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Re the octane aspect: thats exactly the point. You CAN run a high compression engine on 95 octane, but the ignition is retarded if the knock sensor picks up pinking. The Honda engine has such a facility. Run on lower octane if you wish, but maybe at the expense of otimum poke, which is surely why a 200ps motor is fitted? As for the calorific value: I know little about Optimax composition, but if it contains oxygenating compounds, it maybe a trifle lower. Otherwise, surely very similar to other petrols in carbon/hydrogen content, therefore calorific value. At this point, I step back lest my elementary knowledge is stretched too far!
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Is Shell really better than the others? Is it worth the extra 4-5 pence per litre? .. >>
Assuming that you want to use super-unleaded, then the extra 5p/litre [or so] is what you will pay for any brand. However, in my experience in the Surrey/S.W.London area, Shell Optimax is cheaper by a couple of pennies than Texaco's super.
Does it have any long term effect on the car? >>
Try asking Shell who provide an online contact with their experts.
www.shelloptimax.co.uk/index.jsp
forum at www.shelloptimax.co.uk/jive3/forum.jspa?forumID=1
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The Shell forum does make interesting reading IMO. Their "expert" has been challenged to prove Shell's claims and I don't think he/she is doing very well. The expert has not even categorically denied claims that Optimax is regular-unleaded and is not super-unleaded! He/she does claim that "The calorific value of Optimax has been measured at 10790 cal/g, which is higher, but not significantly, than that of other fuels."
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All I can say is that using Optimax has smoothed my Mondeo out somewhat. It wasn't a bad runner to start with but it just feels better, how strange is that then or am I just being seduced by the corporate world of advertising?
Long term, who know's what it will do? On the question of fuel consumption, I may eventually get around to measuring it, I have previously measured 33mpg on a normal mixed mileage fill.
I have just filled SWMBO MX5 with Optimax and for the tank it cost exactly £1.89 extra for the luxury of going well with Shell (see, advertising again). The fuel consumption on the 5 can be a bit scary - 25mpg - so I will check out this one more closely than the Mondeo.
Overall, I can't be doing with all the techno-babble. For me I'm with the Ronseal man, if it does what it say's on the tin, I'm in!
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Dave E's comment brings us full circle - Does it do what it says on the tin? Many are sceptical about the claims made for "enhanced fuel".
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I notice the tickover on my new Corolla is better under Optimax, and whilst I haven't undertaken scientific studies on mpg, I'm sure it's slightly better. So I'll stick to the stuff.
There is also BP coming onto the scene with a similar product....
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My car 1.8 Mondeo showed no performance improvement and about 5% better mpg when using Optimax. A bit pointless when it is 5% more expensive....
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I'm a loser, baby....so why don't you kill me?!
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I record all my fuel usage and mileage:
My conclusions fwiw:
1. Supermarket fuel varies but on average I expect to get up to 10% worse fuel consumption.
2. Ordinary Shell/Texaco/BP give best consumption.
3. Optimax makes no difference.
1.6 Fiesta with no knock sensor so higher RON rating makes no difference.
madf
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