Fully is shit on older stuff. the guy i bought my levin off ran fully and it get so thin when hot that it slowly makes its way past rocker cover seals etc so dribles over the engine and stinks lol. dont get that issue with semi. have run semi on starlets for 7years or so 5+on a forged engine and its never given me issues and looks after the internals perfectly. the 4/5e engines are 20 odd years old they where never made to run fully and i honestly.dont understand the obbsesion some people have with wanting to run a modern oil on an old engine tbh. run semi mate and you will know your not going to get an issue and also have spotless internals ;)