A high mile motor in, I hope, hot weather? Probably ok.

The low tension rings aren't going to like the thicker oil, especially on cold starts. You get an oil burner on cold starts, eventually leading to an oil burner all the time as the rings are "abused" on every start up.

That's my theory, based on a little fact.

I'd go back to the recommended oil and stay there. We have a 100,000 mile Lexus and a 95,000 mile Exploder running 5w-20 in blazing hot So Cal--no oil use in either one of them.