As there has been some discussion (again) concerning it causing issues I thought I’d add my own opinion.
My experience with Exol Optima racing two stroke (M124) is that it is an excellent oil that can be used in leaner mixes than many other brands.
Currently, I know that two motors including my own use it @ 50:1. One is a Ø66 x 58 mm TS1 with a Dell’Orto Ø34 mm & expansion chamber. The other is Ø71 x 61 mm Rapido with a Dell’Orto Ø30 mm & gutted, ‘coned’ Clubman type exhaust. Both have recently been stripped & piston/rings, bore & big ends indicated no issues whatsoever through use of Optima.
It really does appear to be a ‘rich’ oil.
I say this specifically as I do not doubt that it would carbon/gum up any untuned/moderately tuned Lambretta engine when used @ ‘normal’ mix ratios.
Simply because I had it to hand, I performed a simple test with my McCulloch (fan cooled) garden equipment. Even @ the recommended 50:1 in chainsaws, trimmers etc, they would not run well on it! They became smoky, boggy & would not ‘rev’ clean. Reverting to the type available from Merchants, their normal performance returned.
The scooter owning Exol Manager in Northampton branch may not do a deal for everybody, but @ £15 cash for five litres collected, that seems an excellent bargain to me.