1) I have never seen any evidence of cavitation in actual use. How would you know?
----------------------- Drive the car for 200 miles, much of it on the freeway at 80 mph or better, come home and immediately drain the hot engine and transmission oil. No bubbles - not one. Nor have I observed any on the dipsticks - engine hot.
---------------- I probably wouldn't mind using Pennzoil on my chainsaw - for that I use whatever old bottle of oil is around.
---------------- I suppose my high mileage vehicle is the 1977 Toyota pick up truck. Odometer flips over at 100,000, and I'm not keeping track but I know it has at least 300,000 on that single vehicle now. Although with that I use Valvoline 20W50 and el cheapo filters installed by the quick lube place.
---------------- If you change the oil regularly - that's far more important than the brand name of the oil. Driving gently helps, too. I always drive gently as traffic permits as the engine and transmission warm up, but once fully up to operating temperature, I've had the Camry at redline in the first three gears (auto trans. upshift at full throttle actually just before redline), and have had that little truck up over 90 so I don't worry about the oil. I think the most stressful action on the oil is when pressing the Camry throttle to the floor to move around traffic at around 50 mph such that the engine downshifts to second gear and engine speed instantly kicks up over 5,000 rpm - and then moves higher. Also - stupid thing on my individual engine only - prior owner had it serviced somewhere that left the intake air temperature sensor out - hidden along the top of a frame rail under the brake booster for apx.
15k miles before I found it. My stupidity with a new (to me) vehicle, I thought that was a grommet on the side of the air box, when actually it was a small hole admitting unfiltered air into the engine. I know for sure the Lucas stopped that puff of smoke on cold start entirely. I look at it this way: if Lucas is 50W and the oil capacity on the 2.2 L is 3.8 quarts, and I'm mixing .75 quarts (20%) with 10W30 Mobil 1 (which if anything is slightly thinner than conventional oil), then the calculation for the weighted average viscosity would be this:
3.8 qts. minus .75 qts. leaves 3.05 qts times 30 equals 91.50 .75 qts. times 50 equals 37.50
91.50 plus 37.50 equals 129
129 (weighted average total viscosity) divided by 3.8 qts. capacity equals 33.95. So I'm running 34 weight oil (warm) instead of 30, but have the benefit of no valve seal seepage over night. The Mobil 1 has the benefit of exceedingly high film strength compared to conventional oil, plus far less viscosity breakdown, and much improved heat resistance. Works for me. I'm not about to change. You're not about to change. We're both happy. Sounds good to me.