There's no definitive answer to this question. There are as many opinions as there are experts.
Everyone knows that the quality of their motor oil determines their car's performance, and they want to find the perfect option. Unfortunately, there isn't one. Japanese auto oils are currently of very good quality. But who can guarantee that their performance won't change over the years? Furthermore, the brand you choose may simply disappear from the Russian market or be discontinued.
Is there an ideal?
The primary guideline for oil selection is the vehicle manufacturer's recommendations. Sometimes they produce their own brands, tailored to the specific engine specifications, while others offer a selection of the most suitable lubricants from other manufacturers.
Sometimes emergency situations arise when an oil change is required and the correct oil is not available. Will using a different oil cause more harm?
How do oils differ?
To understand this, it's important to understand the differences between oils. The three main criteria are composition, viscosity, and the engine type they're designed for.
Oils are available for gasoline and diesel engines. Based on their composition, they are classified as synthetic, semi-synthetic, and mineral. Furthermore, each brand of oil has its own additives. Manufacturers typically don't disclose their product composition, making it extremely difficult to find oils with similar characteristics. This is why many people say that mixing oils from different manufacturers is not recommended.
Synthetics and semi-synthetics. Is mixing possible?
Only in emergency situations, when you need to get to a service station and there's no other option. In these cases, you should drive at low speeds, starting the engine at low RPM.
Synthetic oils are based on vegetable oils, while semi-synthetics are made from petroleum derivatives. These compounds are certainly not conflict-prone, but their long-term use is not recommended. They are acceptable for use for 500-1000 km.
Is it possible to combine mineral and semi-synthetic oil?
The answer to this question is clear: NO! The reason is their radically different composition. Mixing them can lead to engine clogging with sludge, and additives will precipitate. The oil mixture will lose all its properties. Furthermore, its viscosity will be higher than that of either oil individually. This will lead to clogged valves.
The conclusion is simple: add only the same mineral oil to mineral oil, and semi-synthetic oil to semi-synthetic oil (or, in extreme cases, synthetic oil).
What is possible?
The answer is simple: oils with the same base and viscosity grade, designed for a single engine type. They can be produced by different manufacturers. Unfortunately, finding such options is difficult. There are no oil compatibility charts.
Another problem is the large number of counterfeits on the market, whose composition may differ from the original (even to the point of having a different base). The result of combining them is unpredictable.
If you have a choice between adding oil from the same manufacturer but with a different viscosity, or from another manufacturer but with the same parameters, you should choose the latter option.
What to do after mixing the oils?
- Get to the service station;
- Drain the oil mixture;
- Fill in flushing oil (it is also acceptable to use diesel fuel for this purpose);
- Drain what remains;
- Fill with new oil of the appropriate brand.
Further adjustments should be made to the engine's operation: schedule the next two maintenance checks ahead of schedule. When checking the oil level with the dipstick, pay attention to its color. Black indicates clogged filters, which will need to be cleaned.
What is the conclusion?
Mixing oils from different manufacturers is permitted, but only in emergency situations. Driving with such a "cocktail" is not recommended and may have adverse effects on the engine.