Hi all, new here, just picked up a motorhome with a 1987 carbureted ford 460 in it with 45,500 miles on it and I'm getting ready to do my first oil change. All the parts stores here tell me 5w-30 or 10w-30 is recommended, but being this is an older motor that I'm sure has had some severe duty on it such as towing and going over passes, would it be better for it to run a 40 or 50w oil in it? The motor runs fine and idles good, it doesn't seem to smoke at all but it does have some seeping in the usual places. I've read some posts in ford truck enthusiasts of guys using diesel motor oil in there older 460's, what do you think?carbureted