Should I be concerned about my "milky" looking oil?

Dear Car Talk

Dear Car Talk | May 01, 1998

Dear Tom and Ray:

I have a 1991 Taurus SHO with 51,000 miles. Last week I had the oil changed and
the attendant advised me that my old oil appeared "milky." When I asked him what
that meant, he could only offer a shrug and a blanker look. The car seems to be
running perfectly. It uses almost no oil between changes and has had its oil
changed every 4,000 miles since it was new. Is milky oil bad? -- Greg

TOM: Could be bad, Greg, or could be nothing. Most likely, it's nothing.

RAY: It's hard to know without seeing the extent of the milkiness. We often see
a milky, caffe-latte-like substance on dip sticks or oil filler caps. If that's
what this guy was referring to, then it's just the result of the condensation of
moisture inside the engine.

TOM: Water vapor is a by- product of combustion. And inevitably, some of it ends
up inside the engine's crankcase. And if you do mostly short-distance driving
(which we suspect you do, since you have a 1991 car with only 51K on it), the
engine never really heats up enough to evaporate and purge that water.

RAY: If, on the other hand, all five quarts of oil came out looking like a
cappuccino milk shake, then you may have much more water getting into the
engine. And that's probably coming from a cracked head gasket, cylinder head or
engine block. And that would be bad.

TOM: But with your low mileage, I suspect it's just normal condensation and
nothing to worry about at all, Greg.

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