That's also been my experience.
35 years ago when I was a messenger driver, I used to put 300 miles a day on my work vehicle. I religiously changed the oil once a week for 18 months on that car, using only Pennzoil.
When I sold that car to my brother in law, it had 121,000 miles on the clock, and ran as good as the day I bought it new.
Still intrigued about this product, though. I want to believe, Normie!
LOL
Well, it won’t ‘hurt’ anything.
Here’s the proble,...aside from the fact that you drive a Chevy...which is unpardonable to a fine upstanding Ford man sush as my bad self...
At almost 200k that engine, even if maintained with love, joy and sacrificial offerings, has wear. Tolerances are now far greater than the factory intended. As such, oil has to work harder and breaks down quicker. That leads to deposits throughout the oil passages.
DO NOT DO A MOTOR FLUSH!!!!
You stand a good chance of plugging those passages and frying bearings if you do. You simply cannot know what is inside there.
On a high mileage engine like that, I’d personally go to 20/50 Valvoline and call it good. Additives can’t erase time.
A couple years ago I did a 400 Ford HiPo build for a desert truck (79 F250) with a Boss351 cam/Edelbrock/Holley/porting...all the goodies. I started with 20/50 Val and a Zinc additive (current oil lacks it and its needed for old flat tappet cams/not new rollers).
That engine will live and die on it forever and ever, amen.
An additive at that stage is the time to start using it, but I just don’t see the benefit even in that scenario.