Milky substance on oil dip stick

'98 Volvo with 140K. when I checked the oil I noticed a milky substance on the dip stick. Does this mean I hve a bad head gasket?

That would be my conclusion also. I suggest that you get the car into the shop a.s.a.p. before serious bearing damage takes place.

Good luck.

Are you losing any coolant?

No, not losing any coolant.

The milky substance is water in the oil, as you suspect, but it may not mean the head gasket is bad, especially since you say there is no coolant loss.

You’re checking the radiator, right, and not just the overflow bottle?

Does the car sit a lot, and/or get driven short distances at low speeds in cold weather? If so, you may just need an oil change and a highway drive now and then to cook all the condensation out of the oil.

Don’t guess about a head gasket. There are tests that can be performed to verify a bad head gasket. Try the easy, inexpensive things first.

Many cars exhibit this during cold weather. Combustion blow-by contains much water vapor. It’s the PVC systems job to purge these vapors from the crankcase. But sometimes this moisture can condense on the cold dipstick and form the sludge you see…It will disappear when the weather warms up. At 140K miles, your PVC system probably needs a good cleaning from end to end…This will improve crankcase ventilation…

Yes, the milky substance could simply be the result of excessive moisture condensation in the motor oil.

OP–Do you do a lot of short trips (5 miles or less) in the winter months? If so, you REALLY need to change your oil more often and/or make sure that the car is driven for at least 30-40 minutes without shutting it off, at least once per week.

Moisture condensation in the motor oil is nowhere near as injurious to the engine as is coolant leaking into the oil, but it is still not a good thing. This has the potential to lead to severe sludging of the engine, and over the long term, this can cause lots of expensive problems.

Only on the stick or also on the underside of the fill cap?

I drive 30-40 miles to work & back every day. I live in wisconsin & it’s been very cold the last 2-3 weeks. I’m going to change the oil this week-end. Thanks a lot.

I checked the oil cap & it was okay.

I second the PCV Positive crankcase ventilation system needs cleaned/checked