RedMist wrote:You wont get an accurate octane increase. IE you will detonate one day and run wet the next. Toluene is already present in fuels and is used to up the octane rating to that on the pump. As such there can be little or lots dependant on the quality of the base fuel. By adding more to a batch with little toluene it sygnificantly increases the octane. By adding more to a batch already high in toluene you may get no effect... gettit?
Your much better off using a regulated octane fuel. Such as av-gas, or if needed dedicated racing fuels.
Toluene content does not vary as much as you might imagine, and not by enough that it would make more that 0.5 octane difference. So external conditions like air temp/pressure/humidity will be more likely to affect the engine more than any inaccuracy in toluene levels. eg a 6°C increase in air temp requires 0.5octane increase.
Also toluene is much better in turbo engines as an octane improver, it's effect at higher cylinder pressures is better than most other octane improvers.
With regard to the levels already in fuel, if you're living in the upper half of the North Island toluene levels do not vary that much, lower North Island and the South Island are a little bit more variable, but still not enough to cause issues. According to test conducted in 2001-2002 (
http://www.ess.govt.nz/rules/pdf/petrol ... 1-2002.pdf ) Toluene levels were 13.58% average with a standard deviation of 1.98%. 95% of samles were in the 10-15% range. If you're adding 25% additional toluene the difference in octane increase is less than the variability of octane rating of fuel supplied
