its oil change time on me saph cos - its a 1990 H reg with 98k miles up it lol!

am i right in thinking the correct oil to use is 15/50w semi synthetic?

jsut when you read different places n ask people they say 15/50w then its 10/50 then its 5/50 then its 0/50 - im a mechanic so should know this but woul dbe good to hear opinions.....

thanks

Timbo