I recently switched from Mobil 1 15W-50 to to 10W30 after an
intermittent buzzer problem. The problem went from intermittent, ie  2500 rpm
and lower rpm, to a virtually constant buzzing. I then switched to 20W-50 and
in 4 hours of driving the buzzer went off once for 3 seconds.

      It appears that the system is quite system to changes in viscosity.

      These are my observations for what they are worth.

                         JIseman457@aol.com