Which engine oil ??

Is it possible to do a mod to fit a full flow oil filter on a ST 70 ?
Which oil do members use ? The handbook says 20 or 30 viscosity.Do you use a 70`s oil which leaves particles around the crankcase or a modern 10-30 which keeps rubbish in circulation to be filtered out ?

Hi rocketray, I use a oil called ROCK OIL 10W40 mineral in my st70 and it seems to work a treat