Lube Tips by Jack Poley
1. Viscosity: Always important, but must be evaluated in context in a Used Oil analysis...
2. Silicon (Si): A ‘chameleon’ test result possibility...
- Abrasives: commonly as silicon dioxide (“sand”)
- Seals: as a silicone
- Oil Additive (defoamant): as a siloxane in polymer form
- Coolant chemistries in diesel engines: as a silicate
3. Zinc (Zn): another ‘chameleon’ element...
- Oil Additive: as roughly half of zinc dithiophosphate, a very common additive
- Galvanizing (passive parts erosion, e.g., plumbing or plating)
- Wear (brass alloying agent)
- Contaminant (when required to be <10ppm, e.g., EMD diesel engine)
4. Copper (Cu): yet another ‘chameleon’ element...
- Most of the time Cu is sourced as a moving part wear metal: brass or bronze, from bushings, thrusts or bearing cages
- Copper can also be found as a result of fuel system problems in diesel engines: injector seals or tubes, and internally-mounted fuel pump seals.
- The cooler core of a diesel engine is another possible source of copper. Most industrial cooling cores, such as found in diesel engines, are made of nearly pure copper.
- Though not popular anymore, copper has been used (in the form of an oleate) as a passenger car motor oil additive. Levels around 150ppm are typical, interfering with precision.