Hi Gambit,
Thanks for that,its reassuring to know.....
By the way,i think you could well be right about previous owner using wrong oil.I topped up with 10w 40(about 1.5L) as well as a oil treatment and it seems to have donea very good job.Have noticed a slight loss of power since i changed previous spongy mesh filter to bog standard Halfords jobbie,is this normal?