Engine Oil Leak
Oil leaks leave spots on your driveway and, if left unchecked, can drop oil pressure to dangerous levels. Most minor leaks are inexpensive to fix early but become major repairs if ignored.
Can I Drive?
Short local driving may be possible only if the vehicle still operates normally, but diagnosis should not be delayed.
Most Likely Causes
- 1
Valve cover gasket leak
The most common oil leak. The rubber valve cover gasket dries out and shrinks over time, allowing oil to seep out at the top of the engine where it drips onto the exhaust.
Very common on high-mileage vehicles and engines that run hot.
- 2
Oil drain plug or oil filter
A loose drain plug or improperly installed oil filter causes leaks immediately after an oil change. Always check for drips 24 hours after any oil service.
Cross-threaded drain plugs require a new drain plug or helicoil repair.
- 3
Rear main seal failure
The rear main seal sits between the engine and transmission. Failure causes a large oil leak at the back of the engine, often dripping off the bottom of the transmission.
Common on high-mileage trucks and SUVs. Labor-intensive repair.
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How to Diagnose It
- 1
Clean the engine with degreaser spray, then run it for 15 minutes. Use a flashlight to find fresh wet oil and trace it back to the source.
- 2
Check the oil drain plug and oil filter first — these are the easiest and cheapest fixes. Look for oil weeping around the filter housing or drain plug threads.
- 3
Inspect the valve cover gasket at the top of the engine. Look for dark, oily residue baked onto the exhaust manifold below it.
How to Fix It
Valve cover gasket leak
On most 4-cylinder engines this is a DIY repair ($20–$50 in gaskets). Remove the valve cover, clean all mating surfaces, apply a thin bead of RTV sealant at corners, and install the new gasket.
Oil drain plug or oil filter
Tighten the drain plug to spec (usually 25–30 ft-lbs) or replace with a new washer. Hand-tighten the oil filter plus 3/4 turn — never over-tighten.
Rear main seal failure
Shop recommendedDIY is possible but requires removing the transmission or flexplate/flywheel. Most owners choose a shop for this repair.
Parts & Tools
Enter your vehicle on the home page to get vehicle-specific parts links.
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Other Engine Issues
Browse more diagnostic guides in this category.
Bad Ignition Coil
A weak ignition coil can cause one-cylinder misfires, rough running, flashing check engine light, hard starting, and poor acceleration. Coil failures often show up under load before they fail completely.
Bad Injector Symptoms
A bad fuel injector can stick open, leak, clog, or fail electrically. It can cause misfire, fuel smell, hard start, black smoke, poor mileage, or cylinder washdown.
Bad Injector Symptoms Diesel
Bad injector symptoms diesel engines typically show up as rough idling, excessive smoke, and reduced fuel economy. A failing fuel injector can damage your engine if left unaddressed, so diagnosis and repair should be prioritized.
Bad Injector Symptoms Diesel Smoke
Bad injector symptoms diesel smoke are a serious warning sign that your fuel injectors aren't atomizing fuel properly, causing incomplete combustion and visible exhaust. This condition reduces power, increases emissions, and damages your engine if ignored.
Bad Spark Plug Symptoms
Bad spark plug symptoms include rough idle, engine misfires, sluggish acceleration, and reduced fuel economy. Spark plugs ignite the air/fuel mixture in each cylinder on every combustion cycle — worn plugs misfire repeatedly, wasting fuel and stressing catalytic converters.
Bent Car Rim Symptoms
Bent car rim symptoms include vibration, pulling to one side, and uneven tire wear that develop after hitting a pothole or curb. A bent wheel compromises handling, accelerates tire damage, and can eventually cause a blowout if left unchecked.
Mistakes to Avoid
- Don't use "stop leak" additives as a permanent fix — they can clog oil passages.
- Don't over-tighten the drain plug — stripped threads are a bigger problem than the leak.
- Don't ignore oil on the exhaust — it's a fire hazard.