Just what I do...after 45yrs in the business. ZRod 20w50 is a ZDDP detergent oil from Amsoil I've run it for about 8 years. Uncle Hubie used 30 wt Quaker State since new. When we got 'Bertha' in 1976 I switched to 10w30 Mobil one. While doing the first oil change I stuck a finger in the pan a goodly amount of sludge came out. It's now pretty darn clean after 37yrs of twice year oil changes with a full synthetic oil....doesn't leak any more now than when we got her, no blue smoke I do not depend on 'carbon deposits' on the cylinder walls to prevent blue smoke. Snewpee's look'n better at every post, 303 Protectant will help that top a lot, I use it on everything under the Sun for UV protection.