4 or 5000 miles/3 years (7.5 quarts). 2001 Silverado, 496 cube big block, has 150k on it. Was owned for a long time by an older man who ran Mobil 1 in 4k intervals. The truck lives a relatively easy life, minus some occasional romping. Gets 18 MPG. 8 city. 10 highway.
I was surprised to see bits and grit. There were several little shiny hard bits in the filter that were jagged and not magnetic.
This oil change was its first run of M1 15W50, and a 160 degree thermostat (and a bottle of MOS2) which surely is the grey goo. In the winter I drained a few quarts out (fumoto) and replaced it with plain M1 5w30. Thin the mix out for the cold.
The general consensus is M1 15W50 is safe to use and was the spec'd viscosity for the identical 8.1 used in marine applications. The 8.1 aluminum intake has a flawed pcv setup that sucks in oil vapor, the thicker oil and lower operating temp stops that. Otherwise, a quart every 1000ish miles will disappear.
It sits for 3-4 months without being started sometimes. Engine is always quiet, minus a little growling noise on any cold start, no tapping or ticking. Oil pressure is good/great.
Might send a sample after a couple thousand miles.
I was surprised to see bits and grit. There were several little shiny hard bits in the filter that were jagged and not magnetic.
This oil change was its first run of M1 15W50, and a 160 degree thermostat (and a bottle of MOS2) which surely is the grey goo. In the winter I drained a few quarts out (fumoto) and replaced it with plain M1 5w30. Thin the mix out for the cold.
The general consensus is M1 15W50 is safe to use and was the spec'd viscosity for the identical 8.1 used in marine applications. The 8.1 aluminum intake has a flawed pcv setup that sucks in oil vapor, the thicker oil and lower operating temp stops that. Otherwise, a quart every 1000ish miles will disappear.
It sits for 3-4 months without being started sometimes. Engine is always quiet, minus a little growling noise on any cold start, no tapping or ticking. Oil pressure is good/great.
Might send a sample after a couple thousand miles.