Car engines are complex pieces of machinery which operate under a wide range of temperatures, as such you must ensure that you fill it with the correct engine oil. Engine oil not only acts as a coolant and lubricant, it also protects the engines moving parts from wear and corrosion. Here we answer the most commonly asked questions about engine oil.
What do the combination of numbers and letters on a bottle of oil actually mean?
The numbers on the side of any bottle of engine oil refer to the SAE viscosity rating at different temperatures. We’ll use 20W-50 as an example.
The number 20 refers to the SAE viscosity rating when the engine is cold, the ‘W’ stands for Winter. 50 refers to the SAE viscosity rating when the engine is at optimum operating temperature, this is usually around 100ºC (212ºF).
As the oil in your engine heats up it becomes thinner, multi grade engine oils thin less when the car engine is at its operating temperature. This allows the engine to maintain a constant oil pressure.
Why do I need to change my engine oil?
As your car engine burns fuel harmful contaminants build up and are captured within the oil. This degrades the oil within the engine, regularly changing your engine oil helps to remove these contaminants and replenishes the additives which protect your engine.
What is engine oil made of?
Each manufacturer has their own formula, however almost all engine oils are made of between 75-90% base oil. The remaining 10-25% of the oil is made up of a variety of additives designed to help maintain the oils viscosity at high temperatures
The base oil determines the basic properties of the engine oil, whilst the additives enhance the base oil. The additives also help to maintain the base oil and engine components.
Should I use after-market engine oil additives?
No – engine oil manufacturers (such as Shell, Castrol & Mobil) spend millions in research and development to create the perfect balance of oil and additives. The last thing you should be doing is adding anything else to their carefully developed formula.
What is the difference between conventional and synthetic engine oil?
The base oil of all engine oils is either conventional or synthetic.
Conventional base oil has only been refined from crude oil, whereas the base oil for a synthetic oil has undergone additional chemical engineering processes. The extra processes enhance the oil giving it better properties for use as an engine oil.
Is synthetic oil compatible with conventional oil? Can the two types be mixed?
Yes – synthetic engine oils already have conventional oil as part of its formulation, within the base oil.
Manufacturers also spend a lot of time carefully testing engine oils to ensure they are compatible with other brands. This means that as long as you are using oils of the same SAE viscosity rating (e.g. 5W-40) you can mix engine oils from different manufacturers safely.
Can you use synthetic engine oil to ‘break in’ an engine?
Yes – the vast majority of modern vehicles manufactured today are filled with synthetic engine oil from the factory. Lots of racing teams also use synthetic oil to break in their engines. If it’s good enough for a race team, it’s good enough for your daily runabout.
Can you use synthetic oil in any vehicle?
Yes – whether you have an old or new car, high or low mileage, performance car or daily runabout you can safely use synthetic engine oil in any vehicle.
What is engine sludge?
Whilst an engine is running, by-products from combustion contaminate the oil within the engine. Over time these contaminants build up and can form a ‘sludge’, which can settle in the bottom of your engine.
Using low quality oils, not regularly changing your engines oil and maintenance problems can all lead to sludge forming inside your engine.
Why should I use the oil grade that the manufacturer recommends for my car?
Every engine made is designed to use an oil of a particular SAE viscosity rating in order to properly lubricate all the engine components. Choosing an oil which is too thin can cause wear problems within the engine. Choosing an oil that is too thick will cause the engine to work harder and become less efficient in the process.
We always recommend using the correct engine oil for your vehicle. If you aren’t sure what this, you can check the vehicles owners’ manual for the correct SAE viscosity for your car engine. Most manufacturers also put the engine oil rating on the oil cap on the engine itself.
Find the right engine oil for your vehicle at CarParts4Less. With free standard delivery and next day delivery available on many of our products, you can get your engine oil in no time.