8 Signs That Your Car’s Engine Is Affected by Oil Deposits

At Redex, we are dedicated to helping you maximise the performance of your beloved car. However, there are a huge number of things going on under the bonnet, many of which can impact the performance of your engine. One of which is the presence of oil deposits, which can affect your car’s running in the short term and overall health in the long term.

So, to help you navigate possible performance issues caused by this issue – we will explain what we mean by oil deposits, and offer eight tell-tale signs your car may be affected.

What are Oil Deposits?

In high temperatures, the car’s oil – the blood that pumps around the body of your vehicle – solidifies and effectively gets welded onto critical parts of the engine. While oil will continue to flow around the engine, that solidified goo acts as a magnet, adding to the deposits that are already there.

These deposits can have a range of effects on your car’s performance, some of which can help you identify and solve the issues. Here, are eight signs that your car’s engine is affected by oil deposits.

Poor Fuel Economy 


Do you find yourself having to fill up more regularly than usual? The presence of oil deposits, clogging up fuel injectors and once again, coating your spark plugs, can have a negative impact on your car’s mileage per gallon. Having to fork out more on fuel that’s struggling to perform puts a dent in your wallet, so before the expenses ramp up, be sure to get it looked at, or use a high-quality fuel additive, as soon as possible.

Slow Starting

Always a worry for any motorist, the grumble of a slow-starting engine is never a good sign. Even if you do eventually get it started, then be aware that the engine is more than likely trying to tell you something.

It could be that your car’s oil has coated one or more of your spark plugs. If the valve cover gasket or valve drain has leaked, then it’s likely this will happen. Thankfully, it’s not too pricey a fix: give the plugs a clean with a degreaser solution, and replace the valve cover gaskets, making sure to adhere to the manufacturer’s specified torque pressure – sorted!


Overheating Engine  

If the oil gets too thick to ensure smooth movement of the engine’s moving parts, and cool the engine down in the process, then it’ll start to have the inverse effect. If the engine temperature gauge is straining against the heat, then that’s likely a sign the oil is too thick, and there’s coking covering your engine.

Decreased Horsepower

Noticing your sportster isn’t as speedy as it should be, or your SUV is struggling with its loads? You guessed it – oil deposits. And if they’re unchecked, then you risk causing further damage to your motor. Make sure it’s strong out of the starting gate by getting your oil deposits cleaned up.

Oxygen Sensor

Your car’s oxygen sensor lets you know everything’s OK with the oxygen levels of the gas leaving its engine. Screwed into the exhaust system, it transmits the data to the car’s Powertrain Control Module, allowing for an optimal air-to-fuel ratio.

oxygen sensor

If the sensor starts to fail, or if the sensor tip gets covered with oil, then it can negatively affect engine performance and environmental emissions, sending incorrect data to the engine’s computer.

If your car has clocked up 60,000 to 90,000 miles, then its oxygen sensor should be replaced. Book an appointment with your mechanic and they’ll get it replaced for you, ensuring smoother running and a longer engine life.


Another woe caused by spark plugs. Since they’re the catalyst that ignites the fuel, if it’s off by even a millisecond, then there’ll be an ignition misfire – you’ll know this has happened because of the sudden lurching motion of the engine when it’s running.

Much like a slow-starting engine, misfires are caused by a coating of oil from leaky gaskets, grommets or O-rings. Give your plugs a once over, even minimal residue on single spark plug one is reason enough to replace them all.

Low Oil Indicator Light 

If the “check engine oil” light flashes up when you’re driving, then your car could soon be kaput if unchecked. Even if you’ve just stocked up on fresh oil, deposits and blockages gum up its flow, and if it can’t circulate properly, then serious engine damage is on the cards.

If this is the case, the deposits, far from being tiny flakes, are actually huge chunks churning through your engine. If it comes to this, definitely get it fixed as soon as you can. Keep the engine healthy by regularly changing the oil and oil filter – follow the manufacturer’s instructions on how often – and use synthetic oils if you can.

Excessive Emissions

Dirty, clumped-up, or thick oil can increase emissions, harming both your car and the environment. As the fuel injectors’ flow pattern dwindles, the engine becomes less efficient – creating hydrocarbons in the process. This influx results in more deposits in the combustion areas of the EGR system, further impacting efficiency. 

Whatever the problem might be, keep your car performing at its best with Redex. For more information, click here to visit the Redex website and get a better drive today.