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What Percentage of Semi-Synthetic Oil Synthetic?

Question: I know synthetic blends offer longer life and better performance in extreme temperatures than conventional oil, but it is so pricey. So I’m going to split the difference if I can find the right blend for my Volvo. Off the shelf semi-synthetic oil is blended to a specific ratio, but I don’t know what percentage of semi-synthetic oil is synthetic. Does anyone know the ratios in the most popular brands? I plan to start to convert the LPT C70 to a blend this coming summer for extreme-temperature performance than conventional oil at a more affordable price than full synthetic. By picking up a gallon of each when they are on special, I’ll always have oil for the Volvo running semi or the Volvo running fully synthetic.


I am involved with automotives and have worked for these major oil companies. Firstly, before you all go fitting synthetics into your engines – check with the manufacturer if the engine is suitable for synthetic lubricants. It’s a matter of horses for courses. Just because there is an advanced chemistry available does not mean its going to suit anything and everything. In some cases synthetics have been known to be detrimental to the performance, protection and longevity of engine components.

Ok. What percentage of semi-synthetic oil is synthetic? There are various formulations for the major brands. No blender will ever offer you the formulation so it is difficult to establish the ratios. However, it is thought that as long as it contains 20% of synthetic components then it may be classed as a semi. Indeed this 20% may be made up of additives and may not be included in the base oil which may still be mineral. So the term semi-synthetic may be a misnoma.

Fit the recommened oil grade and spec and change as often as you can afford to inside the service interval.

% of syn. in semisynthetic oil?

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