Shell's New Optimax Extreme

[wrx365]

Originally Posted by buickman

I've tried BP ult & have found no difference to Shell's Optimax Mobils Syn or Uniteds Boost 98 on running or performance in A VCT pwrd AU.
But my nephew has a 2000 WRX that has had a lot of engine mods & when his filled up with BP ultimate the car losses performance & will only run to its best on Mobils synegy or Shells optimax. Speaking to him his still not sure about using ethernol in his car even at 100 Octane

Even though all the high octane fuels are rated 98RON, each are refined differently. Shell OPtimax and Vortex 98 both are refined using aromatic compounds to increase their Octane rating, whilst BP Ultimate used a different method to achieve their 98 Octane rating. The advantage for BP it produces a much cleaner fuel, compliant with new Euro III emission laws, however it is a lesser denser fuel than Optimax, Vortex 98 and Mobil Synergy 98. And as we know the denser the fuel the more power it can help produce.

In standard tuned cars you should notice little or marginal difference between the 98 Octane fuels. There are come cars have with smart ECUs like the WRX that can adjust settings depending on the fuel being used.

However with modified cars you should continue to use the same density type fuel the car was tuned in. It sounds like with your nephews car it was tuned with Optimax and BP Ultimate.