Why is my diesel engine pushing oil out the dipstick?

Oil is an essential additive for car engines, whether diesel or petrol. Your diesel engine might be emitting oil from the dipstick orifice for several reasons. When a car loses oil, it is on a downward spiral, as complete engine seizure is sure to occur unless you take urgent action.

Definition of a dipstick

A dipstick, according to Mr. Car Man, is a long, thin measuring device for checking how much oil is in your car engine. It resides in an orifice, sometimes called the dipstick tube, and gives vital information about the car’s oil level to the driver. You should check your oil level weekly, according to The Haynes Manual on Diesel Engines. This way, you can nip oil leak problems in the bud.

Oil level top-up overfill

If you inadvertently overfilled your engine with too much oil when doing your last top-up, the excess might be escaping via the dipstick tube. Too much oil in an engine can cause problems, just as too little oil can. Check your dashboard display for any warnings about your oil level. Check your dipstick to see whether it is indicating an oil level of more than the maximum permitted amount. Check your car manual, if you need to, to find out how much oil your engine can hold.

Dipstick seal

Some dipsticks have a seal on them to prevent oil escaping via the dipstick tube. The seal is usually formed by one or two rubber o-rings that sit between the pull handle and the start of the dipstick blade. The seal effectively bungs up the orifice so any oil that gets that far up the tube is unable to get any further. If your dipstick has lost its seal, this might be the reason for the oil leakage.

Misreading of problem

In order to be certain the oil is being pushed out via the dipstick tube, you need to run your engine with the bonnet up, so you can work out what is going on. Oil is often dark and engines are often dirty, so it is not always easy to identify the precise source of a leak. The oil could be being spewed out from elsewhere and be travelling to the dipstick tube region.


The problem may also be caused by a malfunction of the positive crankcase ventilation system or excessive blow-by therein. Forgetting to replace the dipstick, or not fitting it back tightly, could also cause this problem. If you spilled oil when withdrawing the can, after pouring some into the filler cap, this might have found its way to the dipstick tube. Further, the liquid you think is oil might be a different liquid, like power steering fluid or brake fluid, which could indicate a different type of problem.

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About the Author

Frank Luger had his first educational resources published in the early 1990s. He worked on a major reading system for Cambridge University Press, became an information-technology adviser and authored interactive whiteboard resources for "The Guardian." Luger studied English literature and holds a Bachelor of Education honors degree from Leeds University.