I have a 90 4Runner with the V6 engine. I bought used with 41k on the odometer in 1997. I used castrol 5-50 syntec from then untill 2002. I had 130k miles on it then and needed valvework. After a long issue with the repairs, I started using M1 5-30 synthetic. After about 5 months, it had to go back to the shop to fix a screw up that the shop did and had not realized it. When I got it back, It had a very slight knock that comes and goes. They said it was in the upper end and the lower was good, and thought it might be a cam bearing or cam drive gear. They double checked those but could not find a problem. I should have made them fix that but it was a long ordeal as it was. Now they are out of business. Anyway, Ive put 20k miles on it now and the knock seems to be only slightly worse. You hear it at idle, but no where else. I have always lost oil between my 4k oci but have not been concerned. I am down a quart of oil every 3k miles. A friend said the knock may be an oil flow problem somewhere in the upper end. I now have 158k on the engine. I need to get to between 200k and 250k over the next 3 to 5 years. I dont want to spring for an engine rebuild. Oil pressure seems kind of lowish at a hot idle, but will come up well as the revs comes up. My question is: What oil should I use based on these things? Id like an oil that can stick well to the cam parts just in case the knock is a lack of lube untill something gets splashed. Id also like to lessen oil consumption. Id like the engine to run quieter. Id like a lower cost per oil change. I in the south east so I see temps of mostly 30* to 50* winter and 85 to 95 summer. I read that the Delvac 1300 15-40 is good and I use that in my boat motor. Would that be a good option for me or should I use something different? I have an analysis kit comming to me as I write this. Any advice?