Rust in Engine Oil? – Fix ASAP!

Have you ever seen a brown substance in your engine oil? This is an indication that the engine oil may have rust. 

Engine oil that has rust can be a sign that coolant is leaked into it. This is also a sign that engine parts may be corroded due to water particles in the oil. We will discuss in detail the causes of oil rust.

How can rust build up in engine oil

To combat wear and tear, engine oil has a sulfur additive. The sulfur in engine oil can react with coolant and water to form sulphuric acids in the oil. Metal that comes in contact with sulfur acid will oxidize and form hydrated iron(III). This causes rust in engine oil.

Oil rust symptoms

  1. Engine overheating
  2. Engine problems
  3. Engine oil with a milky/rusty coating
  4. Corrosion in metal components
  5. Cranking sound

What causes rust in engine oils?

Leakage of coolant or water into engine oil is the most common cause for rust formation. There are many reasons coolant or water could leak into the oil tank.

1. Head gasket blown

The head gasket prevents coolant from getting into the engine oil.  If the headgasket fails, coolant will leak into the oil. Coolant in the engine oil can cause rust to form. This can lead to engine overheating, which in turn can cause corrosion.

2. Car trips in cold weather

If you live in colder climates, moisture can easily get into the oil tank. The cold oil can trap this air. If the car isn’t driven for a long time, the water won’t evaporate. The water-oil mixture reacts to the metal parts and forms rust. This is also called “Rust”. condensation in the oil.

3. Use high-pressure water guns

High-pressure washers can cause water particles to enter your oil tank. This could happen if your oil filler cap isn’t properly installed, or if there’s a gap between the cap and the tank. Corrosion of metal parts can occur when water and engine oil are mixed. This is why you need to do this water out of the oil If corrosion is not severe, it should be addressed immediately.

How can you fix a rusty oil-tank?

  1. You should drain the old oil first to remove any rust.
  2. Thoroughly rinse the tank using water and rust-removal agents like vinegar and baking soda.
  3. You must ensure that all chemicals are removed from the oil tank.
  4. Verify that the head gaskets are in good condition and that there is no coolant leaking into the engine.
  5. Make sure to add fresh oil.


It is important to note that rusty engine oil should not be ignored. This means that engine oil contains water and metal parts can react with it. Engine parts can be permanently damaged if there is a lot of coolant or water that leaks. 

It is important to identify the source of coolant that has leaked in oil. Remove all old oil and drain it before you add new engine oil.

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