Had a chat with an old diesel mechanic that changed how I look at oil

I was grabbing parts at NAPA last Tuesday and this retired guy starts telling me how he never changes oil by the mileage, he just checks the smell and color every morning before starting. He said if it smells like gas or looks like milky coffee, you've got problems no filter can fix. Anyone else do the sniff test or am I overthinking this?

2 comments

2 Comments

blairf489d ago

How often are you checking coolant levels then? @morgan.joseph is right about that milky stuff being coolant, not a filter issue. I had an old Ford van that would smell like gas on the dipstick every third week, turned out the injector was stuck open on cylinder 5. Changed the fuel regulator and it was fine for another 40k miles before the transmission gave out. Smell and color checks are solid if you catch it early enough.

morgan.joseph10d ago

The sniff test is real, but I gotta push back on one thing. He said "no filter can fix" that milky coffee look, but that's actually a coolant leak into the oil, not a filter issue. A filter catches particles, not antifreeze or water. If it smells like gas, yeah, that's usually a stuck injector or a dying fuel pump dumping raw fuel past the rings. I've had a few trucks where the dipstick smelled like a lawnmower gas tank and it was the fuel pressure regulator leaking internally. Check the coolant level first if you see that milky stuff, or you'll be buying a head gasket sooner than later.