I have a 63 coupe Nova with a 250 six and use it around town and some 200 mile trips then it sits for a month. I use 20-50 oil. It usually used to get only 30 weight but I changed at the advise of a nova nut. I do not race it but the summers get hot in so cal and it always seems the six runs hot but that may just be normal. Is this oil weight ok to use as I am afraid to take to Jiffy Lube as they never have the right weight and they want to put 10-40 in it. What is the advise of you guys? The engine has around 5000 miles on it after a rebuild and runs nice.