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Shell Optimax VS BP Ultimate
- Thread starter Nebdingo
- Start date
len_beach
ClioSport Club Member
E92 M3,172 track car
Sainsburys 97 because it only costs 2p more a litre than 95.
IMHO, all this 98 stuff is over hyped. The price difference of a full tank of Ultimax does not justify the extra 'power' or 'cleaning' qualities that they are supposed to offer.
With the 6-7p a litre saving you would have by using the Sainsburys 97, you could afford a bottle of proper engine cleaner (like Forte) once every three months and still have a boat load of cash to spare.
IMHO, all this 98 stuff is over hyped. The price difference of a full tank of Ultimax does not justify the extra 'power' or 'cleaning' qualities that they are supposed to offer.
With the 6-7p a litre saving you would have by using the Sainsburys 97, you could afford a bottle of proper engine cleaner (like Forte) once every three months and still have a boat load of cash to spare.
Boat load of cash? Must be a boat full of coppers!
Just kidding..!
Just kidding..!
Clio Sport 172 Cup Mk2
Definately optimax. My beastie seems to run better on it. But i agree... there are cheeper options... Murco i think in my area do the cheepest 97ron but isnt optimax 98ron? Im confused...
ps. hi all.. im new on the forum. see ya around.
ps. hi all.. im new on the forum. see ya around.
172 Ph1/Scooby MY00
Cheers 172muscle, welcome. Only thing I'd add is that you need to know where all the Shell or BP garages are if you go for just one brand. I was almost out of juice in St Austell, Cornwall recently and was told I'd have to drive miles to find the next Shell station. Had to buy some duff stuff instead.
Clio Sport 172 Cup Mk2
Found a very usefull set of info about octanes and the type of fuel for our beasties (cars)
follow the link. http://www.thor-racing.co.uk/Octane_Rating-149.asp
or read some of this! V interesting.
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons (reduce octane in winter) to obtain the most cost-effective fuel without loss of driveability.
Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realising that you have, could be expensive engine damage.
Back to Top
Does low octane fuel increase engine wear?
Not if you are meeting the octane requirement of the engine. If you are not meeting the octane requirement, the engine will rapidly suffer major damage due to knock. You must not use fuels that produce sustained audible knock, as engine damage will occur. If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long-term reliability. Engine wear is mainly related to design, manufacturing, maintenance and lubrication factors. Once the octane and run-on requirements of the engine are satisfied, increased octane will have no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane rating.
Back to Top
Can I mix different octane fuel grades?
Yes, however attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane. The fuels may not completely mix immediately, especially if there is a density difference. You may get a slug of low octane that causes severe knock. You should refill when your tank is half full. In general the octane response will be linear for most hydrocarbon and oxygenated fuels eg 50:50 of 87 and 91 will give 89.
Attempts to mix leaded high octane to unleaded high octane to obtain higher octane are useless for most commercial gasolines. The lead response of the unleaded fuel does not overcome the dilution effect, thus 50:50 of 96 leaded and 91 unleaded will give 94. Some blends of oxygenated fuels with ordinary gasoline can result in undesirable increases in volatility due to volatile azeotropes, and some oxygenates can have negative lead responses. The octane requirement of some engines is determined by the need to avoid run-on, not to avoid knock.
Back to Top
What happens if I use the wrong octane fuel?
If you use a fuel with an octane rating below the requirement of the engine, the management system may move the engine settings into an area of less efficient combustion, resulting in reduced power and reduced fuel economy. You will be losing both money and driveability. If you use a fuel with an octane rating higher than what the engine can use, you are just wasting money by paying for octane that you can not utilise. The additive packages are matched to the engines using the fuel, for example intake valve deposit control additive concentrations may be increased in the premium octane grade. If your vehicle does not have a knock sensor, then using a fuel with an octane rating significantly below the octane requirement of the engine means that the little men with hammers will gleefully pummel your engine to pieces.
You should initially be guided by the vehicle manufacturer's recommendations, however you can experiment, as the variations in vehicle tolerances can mean that Octane Number Requirement for a given vehicle model can range over 6 Octane Numbers. Caution should be used, and remember to compensate if the conditions change, such as carrying more people or driving in different ambient conditions. You can often reduce the octane of the fuel you use in winter because the temperature decrease and possible humidity changes may significantly reduce the octane requirement of the engine.
Use the octane that provides cost-effective driveability and performance, using anything more is waste of money, and anything less could result in an unscheduled, expensive visit to your mechanic.
Back to Top
Can I tune the engine to use another octane fuel?
In general, modern engine management systems will compensate for fuel octane, and once you have satisfied the optimum octane requirement, you are at the optimum overall performance area of the engine map. Tuning changes to obtain more power will probably adversely affect both fuel economy and emissions. Unless you have access to good diagnostic equipment that can ensure regulatory limits are complied with, it is likely that adjustments may be regarded as illegal tampering by your local regulation enforcers. If you are skilled, you will be able to legally wring slightly more performance from your engine by using a dynamometer in conjunction with engine and exhaust gas analyzers and a well-designed, retrofitted, performance engine management chip.
Sorry there is so much here... just thought it answerd alot of questions i had in mind. 172muscle
follow the link. http://www.thor-racing.co.uk/Octane_Rating-149.asp
or read some of this! V interesting.
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons (reduce octane in winter) to obtain the most cost-effective fuel without loss of driveability.
Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realising that you have, could be expensive engine damage.
Back to Top
Does low octane fuel increase engine wear?
Not if you are meeting the octane requirement of the engine. If you are not meeting the octane requirement, the engine will rapidly suffer major damage due to knock. You must not use fuels that produce sustained audible knock, as engine damage will occur. If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long-term reliability. Engine wear is mainly related to design, manufacturing, maintenance and lubrication factors. Once the octane and run-on requirements of the engine are satisfied, increased octane will have no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane rating.
Back to Top
Can I mix different octane fuel grades?
Yes, however attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane. The fuels may not completely mix immediately, especially if there is a density difference. You may get a slug of low octane that causes severe knock. You should refill when your tank is half full. In general the octane response will be linear for most hydrocarbon and oxygenated fuels eg 50:50 of 87 and 91 will give 89.
Attempts to mix leaded high octane to unleaded high octane to obtain higher octane are useless for most commercial gasolines. The lead response of the unleaded fuel does not overcome the dilution effect, thus 50:50 of 96 leaded and 91 unleaded will give 94. Some blends of oxygenated fuels with ordinary gasoline can result in undesirable increases in volatility due to volatile azeotropes, and some oxygenates can have negative lead responses. The octane requirement of some engines is determined by the need to avoid run-on, not to avoid knock.
Back to Top
What happens if I use the wrong octane fuel?
If you use a fuel with an octane rating below the requirement of the engine, the management system may move the engine settings into an area of less efficient combustion, resulting in reduced power and reduced fuel economy. You will be losing both money and driveability. If you use a fuel with an octane rating higher than what the engine can use, you are just wasting money by paying for octane that you can not utilise. The additive packages are matched to the engines using the fuel, for example intake valve deposit control additive concentrations may be increased in the premium octane grade. If your vehicle does not have a knock sensor, then using a fuel with an octane rating significantly below the octane requirement of the engine means that the little men with hammers will gleefully pummel your engine to pieces.
You should initially be guided by the vehicle manufacturer's recommendations, however you can experiment, as the variations in vehicle tolerances can mean that Octane Number Requirement for a given vehicle model can range over 6 Octane Numbers. Caution should be used, and remember to compensate if the conditions change, such as carrying more people or driving in different ambient conditions. You can often reduce the octane of the fuel you use in winter because the temperature decrease and possible humidity changes may significantly reduce the octane requirement of the engine.
Use the octane that provides cost-effective driveability and performance, using anything more is waste of money, and anything less could result in an unscheduled, expensive visit to your mechanic.
Back to Top
Can I tune the engine to use another octane fuel?
In general, modern engine management systems will compensate for fuel octane, and once you have satisfied the optimum octane requirement, you are at the optimum overall performance area of the engine map. Tuning changes to obtain more power will probably adversely affect both fuel economy and emissions. Unless you have access to good diagnostic equipment that can ensure regulatory limits are complied with, it is likely that adjustments may be regarded as illegal tampering by your local regulation enforcers. If you are skilled, you will be able to legally wring slightly more performance from your engine by using a dynamometer in conjunction with engine and exhaust gas analyzers and a well-designed, retrofitted, performance engine management chip.
Sorry there is so much here... just thought it answerd alot of questions i had in mind. 172muscle
If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long-term reliability.
If we take the 98RON sticker as the 'optimum' and asume that the original writer of that quote knows his or her stuff, then IMO that pretty much answers the 98 v 95 debate. Ergo 95 RON may reduce fuel economy and long term reiability in an engine whos 'optimum' is 98RON.
Then again there is a lot of stuff written all over the web and 90% of it is probably either innacurate or total b****cks. The only thing I know for sure in my mind, is that the RS Clio engines are setup to run at their 'optimum' with 98RON petrol. The side effects of not doing so are probably not that important though.
If we take the 98RON sticker as the 'optimum' and asume that the original writer of that quote knows his or her stuff, then IMO that pretty much answers the 98 v 95 debate. Ergo 95 RON may reduce fuel economy and long term reiability in an engine whos 'optimum' is 98RON.
Then again there is a lot of stuff written all over the web and 90% of it is probably either innacurate or total b****cks. The only thing I know for sure in my mind, is that the RS Clio engines are setup to run at their 'optimum' with 98RON petrol. The side effects of not doing so are probably not that important though.
Nippy white cup
I know a fair few people who get better economy from Optimax which is probably the performance they talk about, not suddenly having more power/acceleration. I get my 98ron from Total now (as it is 1 min from my house) as the local Shell garage is now BP and the nearest is about 10 miles away
Chris
Chris
172 cup
I've always used optimax, but was told recently that Tesco have started selling 99 or 100 ron! I dont belive in supermarket fuel, but does anyone know if this is true, or has anyone tried it?
RenaultSport clio 172
always used optimax
E91 M Sport
I think the '98 ron' minimum for the Clio RS is total arse-talk. They know full well that most countries in the world don't sell 98ron fuel as widely as 95/97. I've never had any issues from running lower-ron (that's 95+) fuel in any standard cars. That's included M3 3.2 and Clio 182 which both 'demand' 98ron or better.
But I still buy it... What a c**k!
But I still buy it... What a c**k!
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