Unpopular opinion: I ran a 6.7 Powerstroke on straight 5W-30 for 500 miles and it didn't blow up

We had a real mess with a 2019 F-250 in the shop. The owner had put some weird aftermarket oil in it and it turned to sludge. I had to flush the whole system three times. I was out of our normal 15W-40 fleet oil and needed to get it running for a test. All I had on hand was a case of full synthetic 5W-30 meant for gas pickups. I figured, what's the worst that could happen for a short drive? I put it in, ran it hard on the highway for about 500 miles over a week, and checked the oil pressure the whole time. It held perfect pressure, even pulling a load. The oil looked clean when I drained it. I'm not saying to do this, but it made me question how picky these new engines really are about weight. Has anyone else pushed the limits on oil specs and been surprised?

3 comments

3 Comments

viola_moore81mo ago

Modern engineering tolerances are shockingly forgiving sometimes.

john_murphy1mo ago

That's playing with fire, man. Modern diesels have crazy tight tolerances and high pressure fuel systems. That 5W-30 might have held pressure, but its film strength is wrong for the bearings and cam. You got lucky with a short run. Saw a 6.7 with the wrong oil spin a bearing after a few thousand miles. The repair bill was more than some used cars.

matthew_reed501mo ago

Man, I used to be right there with john_murphy, totally convinced you had to follow the book exactly. Hearing your story is a real eye-opener though. It shows how robust a good synthetic base oil can be, even if the weight is off. I still wouldn't make a habit of it, but for a temporary fix under watchful eyes, maybe the sky doesn't fall. Makes you wonder if some specs are more about perfect conditions than absolute minimums.