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Synthetic oils are used for many modern vehicle engines. They protect engines from wear, oxidation, and corrosion and have dispersant properties.

There are other benefits of synthetic oils: excellent flow at low temperatures, stable viscosity even at high temperatures, do not require frequent changes, less formation of deposits, less wear on parts, optimised fuel consumption, exceptional engine protection, and longer use cycle.

There is one other oil type: semi-synthetic oils, the mixture of fully synthetic and mineral oils. A semi-synthetic oil is more expensive than a mineral oil, although more economical than a fully synthetic product.

Semi-synthetic oils also offer the same protection features as fully synthetic, such as increased engine performance, excellent parts protection, and optimised performance. Nevertheless, at a lower price point, semi-synthetic oils are less powerful than fully synthetic oils.

Compared to mineral oils, semi-synthetic oils are thinner and more durable. They are also suitable for modern engines and are often preferred as the economical alternative to fully synthetic oils for engines that cannot use mineral-based oils. However, before choosing from any of these types, always consult your manufacturer’s recommendation.

Very often you will come across the values like 20W-40, 10W-50, 5W-40, SAE 30 etc. on packaged engine oil. It is very important to go by the SAE value your car or motorbike manufacturer recommends for your vehicle. To help you understand the simple science behind these values, engine oils are tested by being heated to 100⁰C and passed through a viscosity-meter where the recorded figure gives you the value of the last two digits, in the above-mentioned nomenclature. Now, the digit mention before W is the viscosity value of the oil in a cool temperature condition. So, warmer the engine gets, the thinner the engine oil gets, and the cooler engine is (especially during startup) the thicker the engine oil is. So, ideally what you need is an engine oil that maintains a functional viscosity bandwidth across hot and cold temperatures. You may need to also note that engine oils which simply mention SAE 30 or any other figure after the SAE nomenclature, simply offers you the viscosity value of the oil at 100⁰C and not the cool condition value.

A synthetic base oil is derived though the creation of new base oil components (synthesis) to produce a stronger performing base fluid.

• For a full synthetic motor oil 100% of the base oil composition contains these stronger synthesized base oil components.
• For semi-synthetic or part synthetic motor oils (these terms are largely used interchangeably) the base oil composition is a combination of synthetic and conventional base oils. There is no definition of how much synthetic needs to be included in a semi or part synthetic motor oil.

The use of synthetic base oil can substantially improve the performance of the motor oil. Synthetic base oils

• Improve low temperature performance
• Provide higher thermal stability or heat resistance
• Possess better oil burn of performance or lower volatility
• Enable lighter viscosity motor oils such as 0W-20 to be formulated
• Can help improve motor oil shear stability or the ability to resist viscosity breakdown

The more synthetic base oil contained in a motor oil in general the better the performance.  In turn, a full synthetic motor oil formulated with a robust additive system will always be better than synthetic blends.  That said a properly formulated semi-synthetic can offer performance benefits over a conventional motor oil. 

Adding synthetic base oil to motor can produce a stronger motor oil due to the benefit of synthetics.  Depending upon the amount of synthetic in the base oil composition the semi-synthetic motor oil can be more resistant to the various factors that can degrade a motor oil.  MOTECOL incorporates a material amount of synthetic in our part synthetic formulations to help improve oil burn off performance as well as low temperature flow.  That said a robust additive system is also critical to the overall performance of the motor oil.  Thus, one must consider both in judging performance.  While the incorporation of synthetic can produce stronger motor oils MOTECOL always recommends that one follow the vehicle manufacturers recommendation for oil service and engine oil drain intervals.