The "warm up the engine before you drain the oil" advice I blew off for years
My grandpa always said to run the motor for a few minutes before an oil change on my '71 Chevy, and I figured it was just old timer talk so I kept draining it cold in my garage in Fresno. Tried it his way 6 months ago and the sludge that came out on that first warm drain was night and day, took maybe 10 minutes of idling to see it. Is there a real downside to warming it up like that, or was the old man right all along?