After 10 years, I finally switched from conventional oil to synthetic in my old Cummins and I was wrong about it being a waste

I used to argue with guys at the shop all the time that synthetic oil was just marketing hype for guys with too much money. Been running Rotella 15w40 in my 5.9 for over a decade with no issues. Then last winter when temps dropped to -15 in Denver, my truck sat for three days and I had to wait 20 minutes with block heater just to crank it over. Buddy told me to try Rotella T6 synthetic and I figured what's it gonna hurt. After that change, started right up at 5 degrees with no block heater. Oil pressure is more stable now too, sits at 40 psi at idle hot instead of bouncing between 30 and 35. I still think conventional is fine for most people who run their trucks daily in warm climates but for anyone dealing with cold starts, synthetic actually made a real difference for me. Anyone else have that moment where they had to eat their words about engine oil?

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sarahh818h ago

Did your friend actually see better cold starts after switching too?