my mate has asked me to get him some Castrol A747 for his old yam RD350 circa 1973/74.. i know he's using ordinary two stroke oil at the mo.. via the on-board oil tank... but he would like the smell that you can only get off castrol race oil.... and i know castrol oil won't mix with ordinary two stroke oil..

so

would just putting some in the fuel tank so it mixes with the fuel do ?

or

would he need to strip the engine down clean all the bearings & crank and just use the castrol A747 ?

or

can you just empty the oil tank of two stroke oil and replace it with A747 ?