Originally Posted By: Anies
Hate to break it to you but Varnish will occur regardless of oil depending on the engine.
I've never had visible varnish in any engine I've maintained.
1988 Nissan 2.4 I4 - run exclusively on Mobil 1 5w30 and 10w30 - zero varnish at 150,000 miles
1991 Toyota 1.5 I4 - run exclusively on Mobil 1 5w30 - zero varnish at 120,000 miles
1995 Toyota 3.4 V6 - run exclusively on Mobil 1 5w30 - zero varnish at 130,000 miles
1995 Ford 4.6 SOHC V8 - run exclusively on Mobil 1 5w30 - zero varnish at 110,000 miles
1996 Nissan 3.0 V6 - run exclusively on Mobil 1 5w30 - zero varnish at 120,000 miles
1999 Ford 4.6 SOHC V8 - run exclusively on Mobil 1 5w30 - zero varnish at 100,000 miles
2005 Ford 3.0 V6 - run exclusively on Mobil 1 5W-20 and Pennzoil Platinum 5W-20 - zero varnish at 60,000 miles
2005 Ford 4.6 DOHC V8 - run exclusively on Mobil 1 5W-20 and Pennzoil Platinum 5w30 - zero varnish to date
Sure, some engines are harder on oil than others, so I must have been pretty lucky in that regard.
But then again, I've seen tons of Ford Modulars (which are known to be easy on oil) varnished to [censored] when run on cheap bulk oil, even when changed at regular intervals. See, I've got anecdotal evidence too.