I'm not gonna lie, but I am a bit lost... Let me explain...
- Quick summary if you don't want to read from the start - Heavy oil consumption with 0w40, but when 0w40 oil is thinned with 1qt of MMO consumption goes away.
- Next oil change - straight 0w40. No consumption at first, but slowly consumption returned... Not as bad, but it is there, about 1qt/700-1000 miles.
- Next oil change - Idemitsu 0w20 (Thanks again @Egg_Head) took it on a long trip expecting even higher oil consumption, since the general consesus is that higher viscosity reduces oil consumption, while lower viscosity increases oil consumption... Or so I though. Just did over 1000 miles on Idemitsu 0w20, and the level has not moved... Still right over the full mark, as I filled it during the oil change. Lots of stop and go and spirited backroads exploration.
I mean - I'm glad that oil isn't disappearing (yet), but can't wrap my mind about an old Honda engine from the 90s preferring less viscous oil... It stopped burning when I had 0w40 duluted with MMO, and it's not burning yet with 0w20.
Will keep an eye on it and update as miles rack up.
Thicker oil reduces consumption from the valve seals. Thinner oil reduces consumption from the rings. Add in the fresh detergents and I'm not surprised.