3-second answer: Look at where the oil drips from the lowest point, then trace UP — oil runs down and back. The usual suspects in order: valve cover gaskets (drip down the block sides), rear main seal (between engine and bellhousing), oil pan gasket, timing cover (front). Clean the engine, add dye, drive — then fix what actually leaks.
The leak map (in order)
- Valve covers — the #1 drip. $20 gasket set, 30 minutes. Drips show on the block sides and exhaust.
- Rear main seal — the classic "oil between engine and trans" — it's an engine-out-ish job on these trucks (trans out). Dye test to confirm before you commit.
- Oil pan gasket — drips from the lowest point of the pan. On 4x4s the pan is a fight with the crossmember.
- Timing cover — front drips, oil on the harmonic balancer.
- Oil pressure sender — leaks AT the sender (a $15 part that looks like a rear-main leak because it drips straight down).
The honest advice
- Clean + dye first. A $15 UV dye kit + blacklight beats replacing three gaskets to fix one.
- A small leak that doesn't drip on your floor is often fine to monitor — these trucks leak; it's normal. The rear main on a 300k-mile 5.0 can drip for years.
- Fix leaks that matter: oil on the exhaust = fire risk. That's the one that can't wait.
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