Getting ready to change the oil. What weight do you use/ recommend?

[rhjanes]

10W30 is fine if you are in the northern half of the USA.  Here in the south, I use a 15W40 in my old classics.  I've been using the Shell Rotella T, the old dino-stuff.  A synth or blend should also be fine.  Our temps in the summer are.....toasty, hence the "40". 
Castrol is good oil but I'm wondering which one you got?  I've been using the Castrol, Synth, High-Mileage in my wife's Honda which has 180,000 miles on it.  It runs over 6,000 miles before the car tells me to change it.  Seems like a good oil.  I've also used the Store Brand, which is by "Ashland Refinery" (that's Vavoline).

Exhibit "A" for identification.

I've run that in my 302 and 428, but in a 10W40.  Seemed to run fine. It was a few years ago and I think I used some Zinc in it.  Also used it in a 0W20 Full Synth in the wife's Honda and was just fine.