You may or may not recall the pics of my varnish in my Discovery back when I did my front cover. At the time it was recomended I use chemtool motor flush but I could not find it so I used Gunk instead with ho hum results colorwise. Fast forward to this week I stopped by car quest and found the stuff and decided I wanted to switch over to mobil 1 0w40 and did a flush with a full bottle at idle for 20 minutes. Oil came out black really black. I have another can that I may use on my 2002 corolla that has some varnish. That is after I get the corolla put back together.