This seems to be typical Honda DI behavior: K24W/CVTs produce similar levels of dilution with seemingly no adverse wear results. And readers should note you have gone to a 5w/30 from the spec'd 0w-20.
Here's a Honda thought. LSPI is a fuzzily understood DI/TGDI phenomenon but is potentially catastrophic. Unlike traditional preignition, it can't be controlled with knock sensors that enrich the mixture or retard timing. Instead, engine makers identify where LSPI is possible and enrich the mixture at those points to prevent it. With a CVT keeping revs very low in most Hondas, it could be that simple highway cruising could put the OP's engine in the potential LSPI range, requiring a richer mixture and fuel dilution. My Honda dilutes oil with highway cruising, too.
Maybe Honda is just more cautious than other makers, has concluded fuel dilution is relatively harmless and has decided to live with it if it avoids serious LSPI problems.
OP: you can take these results to your dealer to dealer, but disclosing your use of an unapproved viscosity could create a problem. I've been down this very road with Honda and got nowhere. You could also try using 93-octane fuel as a few DI Mazda users have found this helps. Otherwise, I think your choice to accept this as normal or move to a different make.
Here's a Honda thought. LSPI is a fuzzily understood DI/TGDI phenomenon but is potentially catastrophic. Unlike traditional preignition, it can't be controlled with knock sensors that enrich the mixture or retard timing. Instead, engine makers identify where LSPI is possible and enrich the mixture at those points to prevent it. With a CVT keeping revs very low in most Hondas, it could be that simple highway cruising could put the OP's engine in the potential LSPI range, requiring a richer mixture and fuel dilution. My Honda dilutes oil with highway cruising, too.
Maybe Honda is just more cautious than other makers, has concluded fuel dilution is relatively harmless and has decided to live with it if it avoids serious LSPI problems.
OP: you can take these results to your dealer to dealer, but disclosing your use of an unapproved viscosity could create a problem. I've been down this very road with Honda and got nowhere. You could also try using 93-octane fuel as a few DI Mazda users have found this helps. Otherwise, I think your choice to accept this as normal or move to a different make.
