After trying both a full synthetic and a conventional 15W-40 in my old 7.3 Powerstroke, the synthetic's cold start performance in our Wisconsin winters was the clear winner.

The conventional oil took over 5 seconds to build decent pressure below 20 degrees, while the synthetic was under 3, so what's your go-to winter oil for older high-mileage engines?

2 comments

2 Comments

wells.brooke1d ago

Yeah, that cold start difference is huge for engine wear. I was just reading a forum thread where a guy with a high-mileage Cummins had the same result, even after switching to a synthetic blend. He said the main thing was finding an oil that met the old specs but still had modern additives. For my own truck, I stick with a full synthetic 5W-40 once the temp drops, it just seems to crank easier and get oil moving faster on those first cold mornings.

sullivan.nina1d ago

@wells.brooke You're not wrong about the cold starts. My old truck sounded like a coffee can full of rocks until the oil warmed up. That forum guy hunting for the perfect old-spec oil is basically doing alchemy at this point. Just run the good synthetic and save yourself the headache. Watching people overthink oil is a full time hobby for some folks.