Small amounts of water will likely burn off as the engine heats, but larger amounts of water will change the car engine oil's consistency, potentially causing serious operational problems with the car. Water should never be added to automotive engine oil deliberately, and typically the two substances only mix through condensation, which is normal and unlikely to cause problems. However, water can also enter a car's engine oil through broken gaskets within the car's cooling system, which would need to be evaluated by a qualified mechanic for repairs.
If water has accidentally spilled into a car's oil tank, the vehicle should not be turned on. The oil and filter should immediately be drained and removed to let the system sit empty for a while to allow the remaining water to evaporate. A car that has more than a very small amount of water in its oil may suddenly lose power as it drives, and this may lead to long-lasting engine damage. Automotive oil should appear to be a viscous brown liquid on a dipstick. If the color and consistency is more like that of a chocolate milkshake or another thick substance, this is a likely sign that water has mixed with the oil.