[Thunderhorse]

I don't see any reason to stop using 5W20, but there's no reason not to use high mileage oil. There is a misconception that the seal conditioners in the additive packs of high mileage oils will swell your seals and cause problems, but Dexos 2 criteria requires that an oil not swell seals beyond their original dimensions-so if it meets Dexos 2 then that's not an issue.


IME the Pennzoil made from the pureplus natural gas base stock requires me to add oil between changes, its the only oil I've used where I needed to do that. I have not confirmed but suspect that it does not have a good Noack score.


The only real difference in high mileage oils is the additive package, typically HM oils have greater detergency. Valvoline for example uses sodium as a friction barrier in their regular synthetic, but molybdenum in their high mileage stuff. Nothing API certified uses zinc.

 

[Thunderhorse]

Nothing wrong with pennzoil, but I'd keep an eye on the level. I am using Valvoline