Engine oils - Warning against uncontrolled oil change extensions

Year of publication: 2008



Lifetime engine oils, bypass filters and additional additive mixtures for engine oils are repeatedly advertised. According to the advertising claims, they are supposed to reduce engine wear and fuel consumption and extend the service life of the engine oil many times over. But there is no engine oil, no oil additive and also no bypass filtration with whose help an uncontrolled extension of the oil change interval prescribed by the manufacturer can take place. OELCHECK therefore expressly warns against such uncontrolled extensions of the oil change intervals.

When selecting a suitable engine oil, it is essential to observe the vehicle manufacturer's specifications in the operating manual. Here, the viscosity and quality of the oil are usually specified in detail. Most German vehicle manufacturers also issue a named approval for suitable engine oils. In this case, only the approved engine oils should be used. The labels of the approved oils clearly state: "is approved by... according to...". If no named approvals are available, the consumer should in any case ensure that the engine oil meets the ACEA requirements (for European vehicles) or the API specifications (for other vehicles) required in the operating manual.

Lubricants that are not clearly labeled and that only have a viscosity designation such as SAE 10W-40 should not be used. Also, oils that are advertised with unclear references due to a lack of approval, such as: "meets the requirements," "complies with the guidelines," "developed with regard to the regulations of..." or "can be used for ..." should only be used after consulting the automobile manufacturer.

An unclear choice of words usually indicates that the oil has not been approved by the vehicle manufacturer by name, but is a self-assessment by the oil supplier.

The oil change intervals prescribed by vehicle manufacturers refer only to tested and approved oils. This applies regardless of whether the oil changes are determined by on-board computers from various performance parameters or are specified as fixed intervals. OELCHECK recommends to stick to these intervals at least during the warranty period.

If you would nevertheless like to realize longer oil change intervals for environmental reasons, you should have an oil analysis carried out at the time when the oil change is due. The large number of analysis values determined will clearly show whether it is still worthwhile to continue using the oil.

Our experience has shown that the approach "longer oil use based on oil analysis" often allows a considerable extension of the indicated or usual oil change interval. However, once a longer interval has been found for an oil or vehicle type, it can by no means be generalized. After all, an optimized oil change interval is not only dependent on the quality of the engine oil. The type of vehicle, the fuel used, driving conditions, maintenance of oil and air filters, ignition settings, ambient and oil temperatures, and a host of other factors also influence oil life. Most often, significantly longer oil change intervals can be achieved in long-distance driving, such as commercial vehicles with optimal operating conditions. This is proven time and again by the results of OELCHECK oil analyses, as well as by test bench and field tests conducted by manufacturers.

On the other hand, the oil change intervals can be shortened in the case of predominantly short-distance traffic or other unfavorable operating conditions. Of course, OELCHECK cannot make any generalized statement about which oil is "the best oil" or how long an oil change interval can be extended with which oil. But one thing is certain: Even synthetic engine oils of the highest quality are not suitable as lifetime oils for lifetime filling for motor vehicles.

After all, all oils age, even fully synthetic ones. They oxidize through reactions of the oil molecules with oxygen. Elevated oil temperatures (even above 60°C is high), catalytic impurities and intense air intake accelerate the process.

The acid load of engine oils increases in the course of their use due to combustion products. Blow-by gases, which are also responsible for "acid rain," enter the oil circuit. Sulfur, which stems from the fuel, adds further acidity to the oil. They all have to be neutralized and rendered harmless by the engine oils. As a result, the base number (BN) of an oil in internal combustion engines, also known as the "alkaline reserve," decreases during operation. In fresh oil, however, the BN cannot be raised accordingly because the additives responsible for this are of an organometallic nature and can cause hard deposits, among other things.

Even highly effective additives against oil aging (antioxidants) and wear (anti-wear) can only counteract these processes to a certain extent. If the oil has reached or even already exceeded its performance limit, the engine is at risk:

  • The risk of wear increases, e.g. for the piston rings and the camshaft.
  • Corrosion can occur on the metallic components of the engine, especially on non-ferrous metals.
  • The viscosity of the oil may increase. This makes cold starting and the buildup of oil pressure more difficult. As a rule, oil and fuel consumption increase. Often, exhaust emissions (catalyst poison) are also extremely negatively affected.


Conclusion: When selecting engine oil, be sure to follow the vehicle manufacturer's instructions in the owner's manual. If you want to extend fixed oil change intervals or those calculated by the on-board computer, do not take any unnecessary risks. Have the remaining performance of the engine oil analyzed by OELCHECK.