You're on track with Pennzoil, I would work NAPA engine flush into your routine it's easy to get and effective at a manageable cost, $4.49 in my area.
How much percentage of synthetic blend oils like Castrol GTX HM and PYB are actually synthetic? Is there a way to know?
Sounds good. I'd stick with the Rislone and give it another shot next time around, you may have cleaned up the ring packs too. Two back to back doses might get things nice and clean. You can't go wrong for the cost of it either.Poured a bit of MMO in during the last thousand on several occasions. Tried HiMi Rislone this time. Actually seems to have shut down some light oil burning, something MMO (probably because it burned off) didn't.
The question is does it actually gain you anything?
GII 60% / GIII 40% - 15% Noack
GII+ 70% / GIV 30% - 10% Noack
https://www.infineuminsight.com/en-gb/articles/base-stocks/Which Mobil oil still uses group II stocks?
Well me personally, I am just looking for as “pure“ of a group II 5w30 I can find if that even exists.
I intend to throw some HiMi Rislone in for the next change too, as soon as the Valvoline Daily Protection burns down a bit. Always found VWB to burn off a bit in any car I've used it in. Interesting the OP wants to use conventional, I'd be using full synthetic except I'm a geezer living in a condo where they'd send me a warning letter if I was seen under the car, haven't changed my own oil in 25 years. If I did, it would be a no-name syn like WPP all the way. However, in addition to not being able to drop my own, I have a bunch of $10 oil, filter and rotate coupons to burn through.Sounds good. I'd stick with the Rislone and give it another shot next time around, you may have cleaned up the ring packs too. Two back to back doses might get things nice and clean. You can't go wrong for the cost of it either.
This is as good a place to put this comment as any. It seems when I got on here in 2002 there were a lot of comments that the add pack was more important than the base oil and that a strong conventional like PYB was the way to go. Don't here that much any more.
May I ask why you are trying to avoid Group III?
Check the VI in the PDS sheets. The lower the VI, the more likelihood of it being a conventional.
https://www.machinerylubrication.com/Read/29113/base-oil-groups