I found tan color sludge in my oil, isn't that due to a water leak?

If you are just looking under your oil cap on the top of the engine, that is a common thing. It's when you drain your oil into an oil pan and it looks like a vanilla smoothie. That's when you worry. That's just a little moisture from starting and stopping.

That is residual moisture build up in the engine. This will sometimes happen when the PCV system is not working properly in the engine. Locate the PCV valve and replace it and clean out the coffee milk shake residue on the cap. It will take care of your problem. Good Luck