No, there is no risk of anything bad happening with the 5-50. The probably answer to your consumption issue is the fact that you're using M-1...along with the noise increase (discussed last week)...consumption is very frequently an issue with all of their grades in a lot of engines....
Change the thermostat. Continue the run with the 5-50 and then consider changing brands or back to a 5-40. Or continue with the M-1 for another run. It may very well be cleaning things out in your first run (or first couple of runs) and hence the consumption.
Change the thermostat. Continue the run with the 5-50 and then consider changing brands or back to a 5-40. Or continue with the M-1 for another run. It may very well be cleaning things out in your first run (or first couple of runs) and hence the consumption.