Hello all, it's me again, the relative newcomer to the ranks of Volvo-dom, and so far I like what I see. Quality components, fit and finish, made to last, well thought out, over-engineered, just what I like. I bought a one owner 1992 940GL with low miles about 1,500 miles ago. At least the owner was fairly religious with regular oil changes, that would be done at the dealer with incentive coupons. There are holes in the service record as reflected in the Maintenance Booklet and the invoices I inherited with the car. I live in Dallas where it can get really hot in the summer. The engine appears to have had mineral 10W-30 oil, Castrol, for quite a while. I have had good effects going to a semi-synthetic on both VW and Porsche, ie, valve clatter on startup virtually GONE, and I am wondering at the same time whether a heavier oil might be better. I can see plenty of room in the chart in the Owner's Manual to go to a 15W-40, how about a 20W-50? It can get a little cold here (not like Sweden) for short spaces of time, but in German cars I never had any problems with a thicker oil in winter. What do we think about this? Thanks a bunch.