Shell Optimax, BP Ultimate, Mobil Synergy 8000, Caltex Vortex.....?
01-24-2003, 01:40 PM
#11
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Vortex and Optimax are definitely not the same. Vortex is 96 octane and Optimax is 98 for starters. While I wouldn't be surprised if Shell, Mobil and BP had some kind of arrangement to share base stock, the additive packages are different between brands. Also, they may have been the same in the early days but the more recent news seems to be that the individual brands really do make their own.
01-25-2003, 02:38 PM
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Yep.... fuel 'additives' (plus others) are a BIG load of 
and are nasty for your engine!! 
If you're caught without PULP, just use ULP and go easy on the revs until you can refuel with PULP.
and are nasty for your engine!! If you're caught without PULP, just use ULP and go easy on the revs until you can refuel with PULP.
01-27-2003, 10:34 PM
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There was a long discussion about this on the www.skylinesdownunder.com forum some time ago. One fellow even went so far as to have some fuel tested at a lab.
The conclusion in order of best to worst was: BP Ultimate, Mobil Synergy 8000, Shell Optimax.
For stock engine applications I would think it would make little difference which one you used, but there were a few anecdotes in favour of particular fuels.
The conclusion in order of best to worst was: BP Ultimate, Mobil Synergy 8000, Shell Optimax.
For stock engine applications I would think it would make little difference which one you used, but there were a few anecdotes in favour of particular fuels.
07-09-2003, 04:46 PM
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I was just searching the Shell site and found a new section on Shell Optimax.
http://www.shell.com.au/optimax
Answered a lot of the questions I had and I know some of you have, about the use of Shell Optimax. It takes a look at compatibility, compression, knocking, lean seizures; Optimax and cold starting, spark plugs, density etc.
Great resource for those who may need to tune their engine to enjoy the maximum performance of Shell Optimax.
http://www.shell.com.au/optimax
Answered a lot of the questions I had and I know some of you have, about the use of Shell Optimax. It takes a look at compatibility, compression, knocking, lean seizures; Optimax and cold starting, spark plugs, density etc.
Great resource for those who may need to tune their engine to enjoy the maximum performance of Shell Optimax.
07-09-2003, 05:30 PM
#19
FWIW,
The dyno guy where I tune my race engines recommends Mobil Synergy when you want to use PULP. It produces good horsepower and doesnt foul the plugs. When you are adjusting mixtures you set load points on the rich side and then lean out gradually till you get the air/fuel ratio you want. Optimax can condense on the plugs and if its bad enough can really throw the mixture out due to very slight misfires. The Mobil tends to keep the plugs cleaner.
Octane is not the only thing to look for. Optimax and Synergy are fast burn fuels. They burn a little quicker than a regular fuel which has a similar effect to advancing the ignition a few degrees. I find that I can get good horsepower with a little as 28 degrees advance at full noise when other pulps need as much as 35 degrees. I think this is what gets you the horsepower increases in street cars. The fuel advances the ignition for you so you dont have to rechip/program your ecu.
Many of the Elf special racing fuels are really fast burn and cannot handle high compression. The theory is that the closer to TDC you light the charge, the less time the exploding mixture is pushing back against the rising piston. The faster an engine spins the earlier you have to light the charge. The fuel burns at the same rate no matter what the engine speed is. F1 fuel has to burn really fast at 19000rpm. The aim is to reach peak cylinder pressure at somewhere around 30 degrees ATDC when the piston/rod assembly gets maximum mechanical advantage on the crank. ( depends on rod ratio)
Speedracer.
The dyno guy where I tune my race engines recommends Mobil Synergy when you want to use PULP. It produces good horsepower and doesnt foul the plugs. When you are adjusting mixtures you set load points on the rich side and then lean out gradually till you get the air/fuel ratio you want. Optimax can condense on the plugs and if its bad enough can really throw the mixture out due to very slight misfires. The Mobil tends to keep the plugs cleaner.
Octane is not the only thing to look for. Optimax and Synergy are fast burn fuels. They burn a little quicker than a regular fuel which has a similar effect to advancing the ignition a few degrees. I find that I can get good horsepower with a little as 28 degrees advance at full noise when other pulps need as much as 35 degrees. I think this is what gets you the horsepower increases in street cars. The fuel advances the ignition for you so you dont have to rechip/program your ecu.
Many of the Elf special racing fuels are really fast burn and cannot handle high compression. The theory is that the closer to TDC you light the charge, the less time the exploding mixture is pushing back against the rising piston. The faster an engine spins the earlier you have to light the charge. The fuel burns at the same rate no matter what the engine speed is. F1 fuel has to burn really fast at 19000rpm. The aim is to reach peak cylinder pressure at somewhere around 30 degrees ATDC when the piston/rod assembly gets maximum mechanical advantage on the crank. ( depends on rod ratio)
Speedracer.