New lubricant, improved performance?
Changing your lubricants as easily as changing your shirts – that would be a fine thing! We would buy oils and greases based purely on price, simple storage and immediate availability and it would all run like clockwork. But unfortunately the necessary operating materials are not always that easy to change. Even if two products fulfil a certain specification, changing the lubricating oil or grease type can give rise to nasty surprises. Some lubricants with which positive experiences were made in Europe also bear the same designation in other countries. But their content and their effects on the lubricated components can vary greatly depending on the place of production. It‘s no accident that the topic of „changing brands“ is once more a hot topic for maintainers and international lubricant experts on LinkedIn and other online forums. Using a structured procedure and compatibility analyses could mean that the risks that may arise when changing to another product could be almost eliminated. Better is the enemy of good!
And we should constantly try to continually improve anything concerning machine and system lubrication. Changing the lubricant or oil brand can have many advantages, but can also carry some risks.
When changing brands never forget that lubricant is an essential part of a machine.
This means that such a change is always disruptive to the machine. Prudence is the better part of valour, and you should have good reasons for changing lubricants, such as:
- insufficient protection against wear with the previous product,
- reducing suppliers and lubricant types (storage, mix-up),
- an essential reduction in costs due to lower purchase prices,
- longer oil services lives or relubrication intervals,
- saving energy through improved efficiency (synthetic oils, multigrade oils),
- globally committing to one lubricant manufacturer for all business units,
- the previous product is not longer being manufactured.
You must count on it
Our decision path shown at the right helps you to safely circumnavigate the dangerous cliffs. The important thing is that you follow it to the letter!
Alongside the data sheets and information from the lubricant suppliers, you have access to the OELCHECK Consultation Service.
When comparing supplier specifications you should consider the following characteristic values:
- For oils: viscosity and viscosity index, additive elements, flash point, density, IR comparison and base oil differences.
- For greases: consistency class, element content, IR comparison, bleeding behaviour, temperature operating range, base oil/thickener types, as well as any solids.
Also compare if available:
- Specifications and standards such as: DIN, ISO ASTM and, for automotive products, ACEA and API
- the results of mechanical testing procedures, such as FZG test, VKA (Vier-Kugel-Apparat [four ball test]), Brugger, FE8, foam testing
- Approvals from engine, system and component manufacturers.
In the OELCHECK laboratory, alongside the stated analysis procedures, there are other options for checking individual lubricants and their mixtures. Values exceeding the manufacturer‘s specifications from the data sheets can be determined. This includes, for example, the content of the additive elements and the composition of the additive packages, the filterability, the oxidation stability, avoiding corrosion and performance against water and if air gets into. Performance against sealing materials and surface coating must also often be estimated. A viscosity temperature profile shows whether the lubricant is suitable for use in extremely high or low temperatures. Even individual reactions with ammonia or other cooling agents, fuels, metal working oils, hydrogen sulphide or other aggressive substances can be estimated from the existing data.
It often gets very exciting when a mixture of an old and new lubricant should be evaluated. We recommend that customers carry out mixtures that are easy-to-handle themselves. Then a total of five samples, one from the two fresh oils and three mixtures (at a ratio of approx. 50:50, 95:5 and 5:95), should be sent to the laboratory in the All-inclusive analysis set 2 with the note „Compatibility Analysis“. The oils and mixtures are tempered over four hours at 60°C in the laboratory. This allows the base oils and additives in the mixtures to react together if applicable. If afterwards there is cloudiness, severe changes in colour or even deposits and peeling, the experiments are abandoned noting that the products are definitely incompatible. Fresh oils and mixtures are only investigated further if there are no major visual changes.
The next step is carried out if all criteria of the new oil type have been examined by experts based on the manufacturer‘s specifications or by the laboratory and it has been ascertained that the seals and other system materials will not be impaired. The oil change associated with changing the oil and possibly rinsing and cleaning the system.
- If the old and new product is very similar, the oil can be changed fluently. Shortages can be supplemented with the new product even before the oil is actually changed.
- If both types show greater differences, then you should also factor in the condition of the system. If it is very challenging, old or if multiple malfunctions have already occurred, the old oil must be completely drained. When doing so attention should be paid to the fact that generally more than 5% of the old oil in the system remains on the casing walls, in the bearings and sealing spaces, in the lubricating holes and the lines even during a thorough oil change that includes draining the oil at operating temperature.
- If both oil types are incompatible with each other, the equipment must be rinsed before the oil is changed. Additional cleaning measures may also need to be carried out to remove sludgy and lacquer-like deposits and residual oil. Remember, residue and impurities can also hide in coolers, heating aggregates, tubing, lines, connections and filters!
If the equipment needs to be rinsed before it is filled with the new oil type, the same oil type should preferably be used at a lower viscosity level (at least two ISO VG classes lower). Additional rinsing output can be achieved through warming and circulating at high speed. Do not use additional detergents to boost the cleaning effect or only use them if the operating oil still being used also contains it.
If rinsing with the operating oil or its thinner agent is not sufficient, special chemical cleaning additives can be used. These contain, for example, calcium sulphonate, which is usually dissolved in mineral oil. A disadvantage of this method is that after rinsing, the cleaning oil that is incompatible with all lubricants must be completely removed from the system with another rinse. Hydrodynamic cleaning can be carried out as an alternative to chemical cleaning for large or tricky oil circulation systems. The procedure is based on the application of water, air and flushing oil.
Oils – drain, rinse, change
Unexpected situations when changing oil types
| Negative reactions | Particularly frequent with | Possible after-effects | Precautionary measures |
|---|---|---|---|
| Individual elements of the lubricant separate | Older machines: Changing from mineral oil to lubricants containing ester, detergents, dispersants and other polar additives | Internal and external leakages, insufficient lubrication as possible result | Rinse the equipment and remedy all leakages before the machine resumes normal operation. |
| Seals less efficient (e.g. change to structure and/or dimensions, deformation under pressure, material destruction) | Older machines: Changing to a synthetic lubricant that has a significantly different aromatics content compared to the previous product | Internal and external leakages, insufficient lubrication as possible result | Have the new lubricant examined for compatibility with the seals in the system. Repair/replace old, worn seals. |
| Old deposits and sludge are loosened by new oil | Older machines: Changing from mineral oil to lubricants containing ester, detergents, dispersants and other polar additives | Decreased oil supply causes insufficient lubrication and accelerates wear | Thoroughly clean the whole system by rinsing under high pressure before refilling. Possibly use chemical cleaning additives. Possibly hydrodynamic cleaning by specialist company for large systems. |
| Lubricant is insufficiently effective due to incompatible additives of base oils | Mixing incompatible lubricants together, their acids/bases react with one another. |
| Carefully drain the old oil and rinse in order to remove all residue of the old lubricant. |
Lubricating greases behave differently
Lubricating greases that have proven effective for an application should not be mixed if possible. Depending on the thickening or base oil type, they can be so incompatible with one another that they even lose their structures and become extremely soft upon mixing. However, if a new grease must be chosen, the following criteria must at least be followed:
- the base oil basis (mineral oil, PAO or Ester synthetic oil) must be the same.
- the base oil viscosities should be a maximum of one ISO VG class different from one another. Unfortunately, this information is often very difficult to obtain from the manufacturers.
- the thickener types must be compatible.
- the NLGI classes and grease consistency (penetration) should be identical.
The following overview shows which lubricating greases are compatible, less compatible and not compatible at all.
Each lubricating grease is therefore so incompatible with at least one grease with a different thickener that damage to the lubricated components occurs within just a few days. Greases containing an aluminium or calcium complex soap or that stick to the oil using polyurea or betonite thickeners are amongst the least compatible.
If incompatible greases are mixed, their structures change. This almost always results in a serious softening: the previously firm greases become „soupy“ and begin to „run“. It is uncommon but lithium soap greases can also become firmer. If betonite soap greases are mixed with barium complex greases, base oil frequently deposit on the surface.
However, even if the thickeners are compatible, it can result in difficulties with the base oils or the additives. Greases are not even compatible within a thickener group. Polyurea greases especially bleed, which can only be counteracted with extremely short lubrication intervals. Ultimately, only investigations in the OELCHECK laboratory and discussion with the diagnosis engineers can provide information on whether and how greases are likely to react with each other and which reactions can be expected when mixing.
Some precautions should be taken if a lubricating grease must be changed. First check whether:
- the old grease can be rinsed out of the lubrication points in a relatively large amount of the fresh grease
- the bearing requires more than the minimum amounts due to its design. Otherwise undesirable high temperatures can occur when changing necessary over-lubrication due to filling losses.
If there are no concerns then nothing is stopping the grease change. When lubricating using a handle grease press, it is best to proceed as follows – the same for central lubrication systems or „grease cups“:
Only lubricate with the new grease if the old grease has been used as much as possible and a new lubrication interval is due, for example. If possible, slowly put the new fat into the running bearing until the emerging grease changes in colour or consistency and the residual grease is the same as the fresh grease. Repeat the procedure after a few hours. This means that any residue from the old product is easier to remove. Halve the four subsequent lubrication intervals, e.g. instead every two weeks instead of monthly, over a period of four months. You should be prepared for the fact that during the change-over phase, which can last up to six months, there is a considerably higher grease consumption and that grease disposal can be problematic.
After changing, check
Even if everything is running smoothly after changing oil or grease types, stay vigilant! Surprises can happen to anyone!
- Monitor the systems with continuing lubricant checks and analyses.When carrying out these checks pay attention to foam, cloudiness, increasing temperatures, vibrations, noticeable running noises and grease that leaks or bleeds out.
- Have a lubricant analysis carried out in the OELCHECK laboratory a few operating hours (max. one week) after changing oils.This sample serves as a reference for further trend analyses and for monitoring whether there is residual oil content in the flushing oil. You only have confirmation that everything is in order if the analysis gives the green light.
- And don‘t forget to use the new lubricant name!Change signs on the system, in the lubricant storage space and on the filling devices, where applicable. Correct the information in your electronic data, purchasing and monitoring programmes! It would be a shame if an error crept in further on in the procedure!
OELCHECKER Spring 2014, page 5 - 7
