Friday, 26 January 2018 14:39

Lube Tip 5: Synthetic Oils vs. Mineral Oils

Query: “Relating to gearboxes on trucks, if the owner/ driver doesn’t know if the gear lubes are synthetic, is there a fool-proof way to determine this without having to send a sample to the lab? Some oil manufacturers colour their synthetic oils, while others don’t. What would happen if the oils were to be mixed or topped up with the wrong oil?”

WearCheck’s answer: The colour of the lube is simply a dye. There are no standards, and manufacturers can and do change colours whenever they please. Unfortunately, there is no reliable way of differentiating between mineral and synthetic in the field. However, because synthetic base oils are white (meaning transparent) as compared to mineral oils, which have a darker natural colour (due to aromatics, sulphur and other impurities), this may be a distinguishing factor.  Note, however, that despite the fact that the base oil of a synthetic is white, the additives can add considerable colour (darkening) to the finished oil.

In the laboratory, you could distinguish synthetics from mineral oil by looking at a combination of physical properties including VI, flash point, pour point and aniline point. There may also be different elemental additive chemistry.

Generally, in the type of application you are talking about, the synthetic gear oil will likely be polyalphaolefin (PAO) based. PAOs are very similar chemically to mineral oils, so mixing the two should not cause a compatibility problem, especially if both oils are the same API classification.

 

However, if a synthetic is required, such as for cold-temperature operation, using a mineral by mistake may cause other problems.

Also, be aware that in industrial applications, some synthetic gear oils are polyglycol (PAG) base stocks, which are chemically incompatible with both PAO synthetics and mineral oils. In this case, mixing will result in serious incompatibility issues.

Social Media links

More stories


Christmas Cheer
For many years, WearCheck has supported the children of St Vincent’s orphanage in Mariannhill with ...
110 Hits
Lube Tip 12: These additives don’t exist - Part 2
Part 2 of 4 WRONG-OIL FORGIVER Lubricants and their additives do not automatically adjust to the env...
180 Hits
Labs open over Christmas
Please note that WearCheck is dedicated to being available all year, therefore some of our laboratori...
94 Hits
WearCheck now a level 2 BBBEE company
We are proud to announce that WearCheck was recently rated as a Level 2 BBBEE contributor, placing th...
146 Hits
Lube Tip 12: These additives don't exist - Part 1
I’m afraid I have some bad news . . . and no, it’s not about the economy. It’s about what I oft...
184 Hits