What using the wrong oil does to your car

We all spend a small fortune on our cars, so it's very important and cheaper in the long run, to take good care of the cars engine over its lifetime. Apart from regular servicing, another important factor is choosing the right oil during an oil change.

What is engine oil used for?

Engine oil performs various important tasks within your car's engine. 

Engine oil, generally speaking, performs the following functions:-

  • It prevents/reduces friction by acting as a lubricant,
  • It acts as a heat pump by channeling heat away from the combustion cycle. This is actually a natural consequence of acting as a lubricant and is really important for most engines especially turbo-engines for example,
  • It acts as a magnet for combustion byproducts, and;
  • It minimises oxidation thereby reducing engine corrosion over time.


What do the different grades of oil mean 

Oils you'll find on the shelves today are generally what are termed Multigrade. These were developed about 50 years ago to prevent the need to change between thinner and thicker oils in the winter and summer.

This means oil now fall between two viscosity grades, for example 10W-40 etc. The W component of the code refers to the winter, or thinner, the viscosity of the oil - the W stands for winter.

The lower the W viscosity the better the oil performs in colder temperatures.

The other number only component, 40 in this case, refers to the oil's performance at 100 degrees centigrade. Again the lower this number the thinner the oil and vice versa.


What is the difference between fully synthetic oil, semi synthetic oil and mineral oil?

Semi synthetic oil or fully synthetic oil?

Synthetic oils are specifically manufactured to provide consistent, superior performance. Their main advantage over mineral oils is that they protect the engine across a far wider range of temperatures - up to an engine's maximum temperature and beyond. They do not have the impurities found in mineral oils or degrade as quickly, and they are thinner, helping to improve fuel efficiency.

Semi synthetic oil

Semi synthetic oils are cheaper than fully synthetic as they are a mixture of synthetic and mineral oil. Engines requiring semi synthetic oil must use at least semi synthetic oil (not mineral oil) but may benefit from upgrading to fully synthetic oil for increased protection and performance.

Fully synthetic oil

As the name suggests, fully synthetic oils are purely synthetic with no mineral oil. They offer the highest levels of performance and are an essential requirement for many modern engines (check your handbook if you're unsure of the requirement for your car).


What are the benefits of synthetic oil?

According to oil firms, synthetic oils give improved fuel economy. That’s because they move around the engine more freely as the engine warms up. This helps the engine reach peak operating efficiency more quickly. They put less strain on the battery at start-up because in low temperatures they don’t thicken up too much.

Synthetic oils are also cleaner and help reduce engine exhaust emissions. The reduction in impurities means less sulphur and fewer of the other undesirable contaminants that aren’t removed from mineral oil during the refining process.


What are the symptoms of using the wrong oil?

1. You Might Start to Get Oil Leaks

You might find that when changing between regular and synthetic oil, even with the same viscosity ratios, during an oil change you start to get oil leaks. This is because synthetic oil has a different flow characteristic to regular and can 'leak out' of smaller spaces than regular oil.

2. Reduced Mileage

Using the wrong motor oil viscosity, especially if thicker than recommended, will directly affect your car's mileage. This is because critical moving parts, like pistons, move less freely.

This adds a load onto the engine and subsequently reduces the car's overall fuel efficiency.

3. Your Engine Might Become Noisy

Older car engines could become noticeably noisier when switching between regular and synthetic oil. This is because, like oil leaks, the difference in flow characteristics means synthetic oil slips through gaps more easily than regular oil.

This could mean that the oil 'slips' through engine clearances more easily when compared to older regular oil.

4. Your Car Might Not Start in Cold Weather

In most cases, if your oil change results in a lower cold or winter viscosity than recommended being used, you may find your car won't start in the morning in very cold climates.

5. You Might Start Burning Oil and Damaging Your Engine

If, during the oil change, too high a 'hot' viscosity is used it can result in some issues. For instance, once you've started the car the oil will begin to lose its cohesive strength and will not be able to lubricate as intended.

This will initially result in oil being burnt and, if repeated over many oil changes, could lead to long-term damage to engine components through damage from friction, for example.


Using the wrong oil will void your cars warranty

If you're car has a warranty using the incorrect oil and fluids will void your warranty so do make sure you are using the right oils to save unnecessary costs.

How do I know what oil may car needs?

There are many oil look up websites available where you can type your registration in and find out all the different oil grades that can be used for your car, this will also be listed in your owners handbook. Or alternatively you can always give us a call on 01803 411920 and we can advise you on the correct oil to use.


We at TQ1 MOT Centre always make sure we use the correct oil for your vehicle, we also only use premium brands so that your car gets the best treatment possible