sam530•2mo ago

Update: I swapped to a 5W-40 synthetic in my old 7.3 Powerstroke for a Michigan winter

I was expecting maybe a slightly easier cold start, but the thing fired up like it was July after sitting for two days at 15 degrees. I thought for sure my glow plug relay was finally giving up the ghost last month. Has anyone else seen this much of a difference just from an oil change?

3 comments

3 Comments

nora102mo ago

My buddy Mark with his '96 F-250 had the same shock last year. He put in 5W-40 Rotella T6 before a cold snap in Grand Rapids. Said it cranked over twice as fast at 10 degrees, and he didn't even need to cycle the glow plugs a second time. He was convinced his batteries were going bad.

wesleyjohnson2mo ago

Sounds like Mark was about to drop a few hundred on new batteries over some thick oil. Classic diesel owner move, always ready to throw parts at a problem. Bet he felt like a genius when the cheaper fix was just changing the weight. My neighbor did the same thing but with his Duramax, swore the alternator was dying. Nope, just 15W-40 turning to sludge.

grant_palmer28d ago

I remember back in 2018 in Denver, a guy on the Powerstroke forum ran 15W-40 year round and swore his starter was shot. Turned out the oil was basically tar at 5 degrees and the batteries were fine. He switched to 5W-40 and his truck started like it was summer. What nobody talks about is how thick oil messes with your glow plugs too. They have to work way harder to heat a colder engine, so you get more cycling and they burn out faster. Bet Mark saved his glow plugs a lot of wear just by switching oils.