I did a search for oil weights, and I found a few references to 20 w 50 and 10w40 oil for 29 spider engines. I went to several autoparts, as well as searching online, and when it comes to synthic oils, there is only high mileage in 10-40, and nothing like 20-50. my engine is rebuild, and has a little more than 1000 miles, so high mileage does not make sense. I really prefer castrol oil, been using it for years, but it seems they do not sell this weight. so, my question is, what are you guys doing? I feel that syn oil is the way to go, but I would have to use like 5-30 or something similar. or am I crazy...thanks guys.