Passenger Car Motor Oil Part I – Type of Motor Oils


Motor oil can be segmented into three basic varieties—fully synthetic oil, synthetic blends, and mineral oil.

Fully Synthetic Motor Oil

Full synthetic oils are derived from crude oil or by-products. They have gone through a chemical process rather than conventional refinement used for mineral oil. Fully synthetic oil molecules are more uniform in shape with fewer impurities and better properties, has better extreme high temperature and low temperature performance. Synthetic oils are generally formulated with higher performing additives. The base oils are categorized by American Petroleum Institute into API Groups III, IV & V. PAO is designated at API Group IV and are a 100% synthetic chemical compound. Esters are the most famous synthetics in Group V, which are 100% Synthetic chemical compounds consisting of a carbonyl adjacent to an ether linkage.

Semi-Synthetic Motor Oil

Semi-synthetic oils, also called synthetic blends, are a mixture of mineral oil and synthetic oil, with no more than 30% synthetic oil, which are engineered to have many of the benefits of full synthetic oil without the cost.  Lubricants that have synthetic base stocks even lower than 30% but with high-performance additives consisting of esters can also be considered synthetic lubricants. API Group II and API Group III type base stocks help to formulate more economical semi-synthetic lubricants. API Group I-, II-, II+-, and III-type mineral-base oil stocks are widely used in combination with additive packages, performance packages, and ester and/or API Group IV poly-alpha-olefins to formulate semi-synthetic-based lubricants. API Group III base oils are sometimes considered Fully synthetic, but they are still classified as highest-top-level mineral-base stocks.

Mineral Motor Oil

Traditional oil, or mineral oil, is what it sounds, oil from deep down in the earth’s crust. The crude oil is refined in a process that removes unwanted impurities such as phosphorus, sulphur, and metals. However, conventional refinement will not remove all unwanted chemicals that can affect the size and structural arrangement of the molecules. As a result, the molecule chains may break and degrade the ability of the oil film to perform all of the critical tasks within an engine. Modern car engines are built with extreme tolerances and the traditional oil simply cannot deliver the lubrication they need.

Why use synthetic oil?

The performance of synthetic oils, is more robust, especially in terms of low temperature pumpability, high temperature stability and protection against deposits. These attributes translate directly into less engine wear, increased fuel economy and longer engine life. They have been developed specifically to cope with extreme conditions found within modern engines. They are much more free-flowing than traditional mineral oils. The biggest benefit is greatly increased in engine protection.

When an engine is first started, mineral oil takes some time to circulate, allowing friction between un-lubricated parts to cause wear. In contrast, a synthetic lubricant starts circulating faster, protecting moving parts within the engine.

Synthetic oils also play a significant part in improving fuel economy. During the warm-up period of a typical car journey, mineral oils are thicker and move slower, thus making the engine thirstier and less efficient. As synthetic oils get to work much quicker, the engine reaches peak operating efficiency much sooner.

Another advantage of synthetic oils is that they’re cleaner and environmentally-friendlier, helping to cut engine emissions when compared to conventional mineral oils. Conventional mineral oils also contain greater amounts of impurities, such as sulphur, reactive and unstable hydrocarbons and other undesirable contaminants that cannot be completely removed by conventional refining of crude oil.

In all these important respects, synthetic lubricants easily outperform mineral oils. Totachi offers significant fully synthetic and synthetic oils advantages such as:

  • Higher viscosity index
  • Better viscosity stability at varied temperatures
  • Better chemical and shear stability
  • Consistent fluidity
  • Better lubricity at low temperatures
  • Faster lubrication at start-up in low temperatures
  • Resistance to oxidation (thickening), thermal breakdown, and oil sludge problem
  • Excellent protection at high temperatures
  • Engine cleanliness
  • Outstanding protection against harmful deposits
  • Cleaner running engines
  • Lower oil evaporation
  • Engine efficiency
  • Lower maintenance cost
  • Fuel economy

Here are a line up of some of Totachi’s highly recommended fully synthetic engine oils:


Before using these products, ensure it is consistent with OEM’s recommendations for the equipment operating conditions and customer’s maintenance practices.

You are welcome to contact us at for more information on our lubricant products!