Andy,
trying to use biodiesel for two strokes model engines means filling the krancase with low viscosity stuff, no hope to have it vapourized when arriving in the combustion chamber, so you will have smoky exhaust and poor lubrification. As for Heptane or Hexane, they are interesting as starters, Heptane has the highest detonability, but hexane has a lower boiling point. This helps for starting. I think they sell heptane mixed with ether since selling hexane mixed with ether for some purposes should be the same as using ether.......you understand.
I don't know how to find Heptane, but Hexane is widely used in laboratories, but not cheap. Hexhane is also sold everywhere as home stain remover, but unfortunately here it is compulsory sold mixed with dichloropropane, that renders it useless for us due to the chlorine content.
For those interested in modified olive, look at this fresh raw data. They have yet to be calibrated in viscosity, and the temperatures higher than 120°C will require another cup viscometer, but the interesting reliabilty of the lubrificant clearly appears to be mantained over an exceptiona temperature range. Another interesting result is that (double) modified oil (dots) is only sligtly more viscous than unmodified one (crosses), notwithstandig the apparent higher viscosity alo I felt.
Unfortunately the sample went lost while trying a third modyfying, in presence of some very fine steel wool acting as a catalyzer, but I made in time to notice how this wool keeps all the impurities arising during heating.
This batch had one particularity, it went from an exceptionally old sample of olive oil kept out from air, but not more edible.
Ugo