VinnyP
i asked Shell about the posssibility of getting Optimax to the IoM, but it would have been rather pricey (double the cost, plus transport fees )
Also, be aware that you can't carry extra fuel on the ferry!
Thus, octane booster seems like the only way for folks like yourselves (i hope that they are legal on the ferry!)?
Still, the island isn't very big, so you can cram the fun into a worthwhile time!!!
mb