CyberJack posted an interesting fuel can (the photos of which I have attached)
It says the Imperial runs a 80:1 mix
My best assumption is that lower compression (head spacer on the imperial) means less temperature, maybe meaning the cooling fins can take care of the cooling aspect more by themselves, leaving the oil more solely for lubrication.
Also, the imperials wouldn�t see use on heavy lawn or really heavy �jungle growth� that the rotarys were often subjected to. That means an easier life, and again less heat. Not being squashed against a mower base, with a fuel tank and big dress cowl covering the engine, probably also helped keep it cool. No governor means a reasonably constant speed for most of its life, like how an outboard is often used.
The lean ratio could probably also be associated by Victa identifying their target market as more discerning than the regular rotary buyer. I guess Victa figured their potential Imperial buyers might have been a bit perturbed by mowing accompanied by something of a smoke haze, and finishing mowing reeking of 2 stroke oil. As Victa was competing with 4 stroke Atco, Qualcast, Scott-Bonnar, etc, this was probably important to them. I supposed they already had a bit of a disadvantage with noise alone.
Regards
Tyler
