OK I may need to plea Insanity 
After running A blend of GC gold and green (before I knew there was a diff) on my 2002 Toyota Tundra V8 for 5k, the urge to change it was overwhelming, so I did.
I switched from OEM oil filter to NAPA Gold over sized Ford filter #1516, I broke out the stash of green, after inserting 5 qts, I kinda had a mental laps,
and took out 2 qts of 5w-30 M1 Truck & SUV, the over sized filter caused me use use more oil (it was expected
) then I found almost a 1/2 qt of syntec 20w-50 so I threw it in 
it runs good. almost threw in a little Havoline high mileage but its full now.
I wont be doing this again, since I wont have anymore M1, and besides the M1 really thinned out the GC, If I ever want to thin out GC I will use PP. Just wanted to clear out the old oil sitting around, dint really want to throw it out. Did I blaspheme 
After running A blend of GC gold and green (before I knew there was a diff) on my 2002 Toyota Tundra V8 for 5k, the urge to change it was overwhelming, so I did.
I switched from OEM oil filter to NAPA Gold over sized Ford filter #1516, I broke out the stash of green, after inserting 5 qts, I kinda had a mental laps,
and took out 2 qts of 5w-30 M1 Truck & SUV, the over sized filter caused me use use more oil (it was expected
) then I found almost a 1/2 qt of syntec 20w-50 so I threw it in it runs good. almost threw in a little Havoline high mileage but its full now.
I wont be doing this again, since I wont have anymore M1, and besides the M1 really thinned out the GC, If I ever want to thin out GC I will use PP. Just wanted to clear out the old oil sitting around, dint really want to throw it out. Did I blaspheme 
I'd say don't fret it, but keep the OCI within reason, and youand your engine will be just fine. To be honest, until becoming a member here, I mixed all kinds of viscosities AND brands for just about every engine I had at one time due to the "leftover quarts of a case"! 
But now, I've been educated... 
