Unusual 'butter' in your engine oil: here's what it means and how to prevent it

The confused reader had a question about an unusual substance he discovered when assessing his car's engine oil level. He found a yellow matter, the consistency of which was similar to butter.

Worried, he questioned, "Does this indicate a defect with the head gasket?" Prior to jumping to any abrupt conclusions, we had a short discussion. It turns out, he uses his car daily to commute to work, covering nearly 6.2 miles (or roughly 10 km). While the engine does heat up, it's not to its full extent. And during the winter, warming the inside of the car is out of the question. His route to work is an easy ride that lasts only a few minutes.

After gathering this information, I was able to make an initial diagnosis. The "patient" doesn't sufficiently warm up, resulting in the accumulation of a significant amount of water in the oil. This is a natural condensation process that occurs on the metallic parts of the engine. The water that mixes with the oil forms a "sludge", often referred to as butter or mayonnaise due to its consistency. Unfortunately, this condition can negatively impact the engine's longevity.

First and foremost, don't panic. Instead of taking the mechanic's advice that instant engine repair is required, it's preferable to follow the advice I gave to the reader. I suggested taking a lengthier trip, about 30 minutes, in such a way that the engine becomes properly heated. Rather than keeping the revs low as he does daily, the reader should maintain a mid-range rev level during this journey, which means shifting gears later than normal.

After this test, most of the "butter" had disappeared, and the engine temperature stayed at the appropriate level. These results confirmed that the issue was the engine's insufficient heating, not a cylinder head gasket defect. Still, I recommended that the reader change the oil, as the presence of water does not favor the engine's protection against friction.

These kinds of scenarios often occur from autumn to spring, especially in the mornings when starting a cold engine. But be alert in the summer, as "butter" in oil is a rare occurrence when temperatures are high.

I advised the reader to modify his route or driving style at least once weekly. It might sound like a common mechanic's humor, but it essentially means to "drive and observe". If there's no change during a longer ride or more dynamic driving, consider switching to a different type of oil.