Viscosity is a measure of the thickness and 'ease of flow' in any liquid. For example, because water is a free flowing thin liquid, we say it has a low viscosity. Honey is relatively thick and flows more slowly. For this reason, we describe honey as high viscosity. It should also be said that honey flows more easily when heated a little bit - and thus has a lower viscosity. Engine oil behaves similarly; This is why mechanics usually run the engine for a minute or two before pouring used engine oil for replacement.
There are many engine oils on the market, which oil is right for your vehicle? There are three basic types of oils: mineral, semi-synthetic and fully synthetic. Mineral oils are the least refined of the three; This means they will provide less protection, performance and efficiency compared to other options, despite their lower price. Semi-synthetic motor oils consist of a mixture of mineral oil and synthetic oil for added performance, but still cost less than fully synthetic motor oils. Fully synthetic oils are the most expensive motor oils because they are highly refined, but offer the best protection and efficiency level for absolutely any vehicle.