What next, discarded fat from a deep fryer? I vaguely recall a Victa instruction booklet saying not to use multigrade oil as the mix as it will shorten engine life.
I bought a mark iv 125 cc and the owner claimed he had used synthetic 2 stroke oil and it certainly had grunt comparable to a 160cc going through thick grass.
I have read somewhere that 2 stroke for outboard boats is not good for garden equipment, due to high ash or something.