Isn’t Mobil1 now claiming that some of their oils are removing sludge and varnish? I seem to remember their piston before and after visual aid/test, where they have a color coded chart. Could be wrong.
I probably would like to see some more evidence that restore and protect can do what they’re claiming it can do…I’ve never been a huge fan of before and after cleaning product photos (things like CRC intake/throttle body cleaners, etc).
Just three days ago a V6 Hyundai came into the shop for an oil change - the vehicle went two years and 35,000 miles between intervals - the oil filter was so heavy with sludge that it began falling apart under its own weight upon removal. The oil fill cap had more than a quarter inch of sludge hardening up under it. From what I could see under it the valve train looked like it was sitting in chocolate pudding. They signed a waiver, we did the oil change using just NAPA house synthetic. Within minutes upon startup we shut it down, the vehicle sat in the bay overnight - the next morning I went to show someone how sludged up and filthy it was under the fill cap, and…it looked completely different. I’d say 75% of the garbage that was stuck to that cap was already gone…under the valve cover looked like it had been pressure washed and nearing “clean” levels. I was completely stunned. Of course the engine probably blew up on the way home - the customers didn’t care, they were going to take their chances - but it was obvious that even NAPA synthetic with modern day certifications can do some serious cleaning. Then again, doesn’t Valvoline make NAPA house brand synthetic?