Is it possible to mix transmission oils and what to do if this has already happened?

Issues discussed in the material:

• What types of gear oils exist
• Is it possible to mix transmission oils?
• In what cases can mixing of oils occur?
• What are the dangers of mixing transmission oils from the same manufacturer or different brands?
• What to do if mixing of different gear oils has already occurred
• Is it possible to mix engine and transmission oil?
• Is it worth it, in the opinion of car owners, to flush the gearbox when changing transmission oil?

Is it possible to mix transmission oils? This question is especially relevant in cases where it is necessary to add a working mixture to the gearbox, but, as luck would have it, there is no suitable composition at hand.

How dangerous is it to mix such liquids? How can this affect the performance of the car? How to rectify the situation if after this the car starts to act up? We will try to answer these and other questions in our material.

What types of gear oils exist

Is it possible to mix transmission oils? Let's first figure out what it is. Transmission lubricant is similar in composition to motor oil. The base base and additives are their main components. Transmission oils can be synthetic, semi-synthetic and mineral. Their choice depends on the drive of the car. For example, for a manual transmission it is better to use a high-density mineral lubricant, and for an automatic transmission it is better to use a synthetic lubricant with medium viscosity.

Before answering the question of whether transmission oils can be mixed, let's consider their classifications. Transmission fluid manufacturers follow the recommendations of the Society of Automotive Engineers (SAE) and the American Petroleum Institute (API).

According to the classification of the Society of Automotive Engineers, the following three viscosity groups are distinguished:

1. Oils that maintain their performance at low temperatures and are intended for the winter period:

• Up to -55 °C – 70w;
• Up to -40 °C – 75w;
• Up to -26 °C – 80w;
• Up to -12 °C – 85w.

2. Oils designed for the warm season. Their main indicator is kinematic viscosity at a temperature of +100 °C (rate of film formation on metal, mm2/s) :

• 80 – 7–11;
• 85 – 11–13,5;
• 90 – 13,5–24;
• 140 – 24–41;
• 250 – over 41.

3. Oils intended for any season have two numerical indicators: one with a “w” symbol, implying winter use, the other – summer.

The American Petroleum Institute classification evaluates the quality of gearbox lubricants and takes into account the amount of additives. They take into account various factors - type of gearbox, drive, operating conditions. For heavy trucks, six groups GL and MT-1 have been developed.

There is no single standard for the production of gearbox fluid. Manufacturers produce them in accordance with individual specifications. They also differ from each other in additives.

Important points

To ensure uninterrupted operation of the hydraulics, the lubricant must meet certain requirements:

The Russian Federation has a GOST that meets international standards. For hydraulic fluids, it is marked with the number 17479.3-85, which corresponds to ISO 3448 and consists of three groups of signs: name, viscosity class, field of operation. Since the hydraulic mechanism operates at fairly high temperatures, the oil used must have a flash point even higher so as not to boil. But the freezing temperature should be low. The substance produced is subjected to careful filtration. However, polymer additives added to increase the viscosity index tend to accumulate on the hydraulic system filter element. The pressure sensor signals this in an emergency

When pouring new oil into the system, you need to check the existing filter in it and replace it if necessary. To avoid all kinds of leaks in the hydraulic system, you need to pay attention to the seals. The material from which they are made must be compatible with the lubricant used

Preference is given to proprietary seals designed for specific hydraulics. Do not mix oils intended for different hydraulic systems.

Is it possible to mix transmission oils?

Uninterrupted operation of the gearbox is possible only if the fluid that performs the lubricating function is replaced in a timely manner. This is what gear oil is designed for. The modern automobile market offers a wide selection of manufacturers. Therefore, many often wonder whether it is possible to mix transmission oils from different manufacturers. Experts do not recommend doing this due to the fact that each liquid is unified. Mixing them is allowed only in extreme cases.

The main component of the lubricant is the base. It can be mineral, synthetic or semi-synthetic. Experts say that if you mix substances from different manufacturers, but with the same base, there will be no harm to the gearbox. However, this is only in theory.

On the other hand, it is worth considering that, in addition to the base, the lubricant contains additives, the composition of which varies depending on the manufacturer. It is worth noting that their production requires large investments and the involvement of a large number of specialists. This is why many chemical companies are proud of their additives.

Is it possible to mix transmission oils, for example, “mineral oil” and “semi-synthetic”? Almost every car enthusiast knows about the types of lubrication bases. There is an opinion among them that by combining a small amount of a mineral base with synthetics, the result will be a semi-synthetic base.

Some claim that it is permissible to mix all types of liquids, regardless of the brand and technology of their production. But this is not true at all.

We strongly do not recommend testing this statement in practice. Otherwise, it will not be possible to avoid gearbox damage. Use only suitable transmission lubricant, do not mix it with other fluids, and then the gearbox will serve you for a long time without any problems.

Possible consequences of mixing

Many motorists, when faced with the need to replenish the volume of lubricant in a manual transmission (manual gearbox), reason trivially - the transmission does not experience severe loads like an engine, therefore, there are no special requirements for replenishing the volume of motor oil.

An inexperienced driver believes that there is no need to worry about the likely consequences of mixing different petroleum products. Often this approach seems to be the most practical, because manufacturers of consumables set different prices for their own products.

The desire to save money can lead to dire consequences. The car may need major repairs. This is due to chemical reactions that will definitely begin if you mix mineral motor oil with synthetic oil. A special precipitate will appear in the form of white flakes. The gearbox will become clogged, including the oil filter. Its parts will be subject to deformation and severe wear.

Automotive service employees claim that most often the transmission broke down due to pouring mixed lubricant into it (mineral oil plus synthetics). When drivers mix car oils, they hope to get a semi-synthetic product. Of course, this is impossible.

At first, the deterioration of the gearbox may not be particularly noticeable. However, gradually you will begin to notice that modes are not switched as smoothly as before, and wear on parts has increased significantly. These are the negative consequences of operating a car with mixed oil fluid poured into the gearbox.

In what cases can mixing of oils occur?

Lubricant components can indeed mix, but only under certain circumstances. Let's say while on the road you are faced with the fact that the oil level has dropped significantly. This can happen in the transmission, differential or transfer case. It is impossible to continue driving without lubricating fluid, because in this case there is a high probability of failure of the unit. It may not be possible to find a substance from the desired manufacturer, but you need to top it up immediately.

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In addition, during a routine replacement of transmission lubricant, it may become mixed with the previous one. It will not be possible to completely drain the old fluid; its remains will in any case remain on the crankcase or gears. When you add a new one, they will mix with each other.

If the vehicle is not properly maintained, transmission fluids may become mixed. This can happen due to the fault of the car owner himself or due to the inexperience of the mechanic in the car service. If the auto repair shop doesn't inspire confidence in you, don't risk it, go elsewhere.

This situation can also occur when purchasing non-original lubricant.

Is it possible to mix transmission oils in a manual transmission? Regardless of the type of transmission, we do not recommend doing this unless necessary. Some car owners like to experiment with their car. They are driven to this by the desire to reduce operating costs or make the car perfect in everything. Remember that mixing transmission oils can negatively affect the functioning of the gearbox and technical processes in general.

What are the dangers of mixing transmission oils from the same manufacturer or different brands?

Is it possible to mix transmission oils in automatic transmissions? As we said above, it is not recommended to do this either in an automatic or manual transmission. But if this happens, the car owner should be aware of possible problems. It all starts with an impressively sized sediment appearing in the checkpoint. Different components of liquids can react with each other, the result of which is unknown.

At first glance, it may seem that the transmission does not bear significant loads, like, for example, its power unit. Does this mean that you can mix gear oils from different manufacturers with the same viscosity? No, its components and elements still require high-quality lubrication. This means that liquids containing different chemical additives cannot be used together. We recommend using the same oil every time you change it. Otherwise, dull white flakes may appear.

There may be very few flakes. If the car owner does not pay attention to this, the device may malfunction due to clogging. The presence of sediment will lead to the cessation of functioning of the entire system. In this case, inattention and negligent attitude towards the car can cause transmission failure.

What happens if you mix lubricants with different viscosities? In this case, the consequences can also be serious. This often happens due to the car owner’s carelessness, for example, when purchasing an oil product from the desired manufacturer, but with a different base.

Is it possible to mix transmission oils from the same manufacturer? No, because in this case, after 400 km, a whitish precipitate will begin to form in the gearbox, and the fluid itself will become foamy. This will lead to thickening of the lubricant, which will significantly shorten the life of the system elements. There is a negative impact on the seals, the pressure on them increases, thereby pushing them out of their place.

Is it possible to do this?

If you take liquids for your car that have the same classification according to API, without additional approvals and manufacturer’s notes, on the same basis, then there will be no harm from mixing. Since their compatibility and interchangeability is guaranteed by this standard. For example, when mixing two gl5 oils, you get a substance that has the same properties, and therefore is suitable for the same operating conditions and units.

It is permissible to mix lubricants of different brands, if the properties are not lost or changed; this applies to oils produced by one factory, only with different stickers. Then they are chemically equivalent, they can be mixed and one substance can be replaced with another. However, sellers of ordinary stores (not company-owned or branded), as a rule, do not have such information. Therefore, when purchasing goods in these stores, you are playing a kind of lottery. I wouldn't recommend this.

You cannot mix automatic transmission oil with mechanical lubricant, compositions of completely different viscosities, the mixture will be equally destructive for both boxes.

What to do if mixing of different gear oils has already occurred

Have you mixed different gear oils? In this case, the lubricant must be changed immediately. Washing liquids will help you do this effectively.

It is best to contact a trusted car service center. Professionals will replace the substance without re-mixing using a special apparatus. But what if the car owner doesn’t know what lubricant to pour into the gearbox? Let's consider several options. If you are the first owner of a car, you should look for information in the owner's manual. If the car is used and you do not have such a brochure, check the information with an official dealer or on the manufacturer’s website.

Summarizing all of the above, the answer to the question of whether transmission oils can be mixed becomes obvious. Doing this is strictly prohibited. Exceptions include unforeseen situations when there is no other way out. Remember that mixing liquids can lead to unpleasant consequences.

If you are in a situation where refilling a substance is absolutely necessary, but the required variety is not available, use what you have.

Keep in mind that it is absolutely forbidden to continue driving with a low oil level. If possible, select the most suitable type of gear lubricant by analyzing its properties and characteristics. Use it, but flush the transmission and fill with the recommended fluid as soon as possible. Try to do this no later than after 200 km of travel.

You can mix transmission oils only in cases of extreme necessity, but it is better not to do this. Be prudent and always carry a canister of suitable lubricant with you. This measure will save your time and money, and eliminate unnecessary problems, for example, you won’t have to go to a car repair shop and wash the gearbox.

Is it possible to mix engine and transmission oil?

Before answering the question of whether it is possible to mix engine and transmission fluid, you should understand their composition and differences from each other. The first operates at high temperatures, and its components include additives developed using complex technologies. Let's look at the main indicators of oil used in an internal combustion engine:

1. Minimum viscosity . This ensures performance at high speeds and makes it easier to turn the crankshaft and drive units.
2. High alkaline index . After fuel burns, acidic compounds are formed. They can have a negative impact on the internal combustion engine. Alkaline additives solve this problem.
3. Detergent additives . They help remove fumes and other deposits formed during engine operation.
4. High turnover . The liquid is able to penetrate into the narrowest gaps of the moving parts of the internal combustion engine and acts on the sealing rings of the piston group.
5. Manufacturer approvals.

Motor lubricants are designed with engine performance in mind. Can they be mixed with gear oils? The operating principle of the latter is slightly different. They must contain a thick base and additives that will help withstand high speeds and critical overloads of mechanical origin.

Features of transmission lubricants:

1. High viscosity . They are approximately 10 times higher than engine oils. The reason for this lies in larger gaps compared to internal combustion engines, as well as the need to increase resistance to destruction at the mechanical level.
2. Low temperature stability . The gearbox does not have the same temperatures as the engine. Therefore, additives of this type are not in demand.

Is it possible to mix transmission oils with motor oils? The answer is obvious - no. The reason for this is the fundamental differences in their properties and characteristics.

Danger of mixing lubricants

Careless mixing of several types of gearbox oils can cause very serious consequences. But the main ones will be related to the design features of the box.

Lubricant operation in gearboxes and gearboxes occurs at low temperatures relative to the operating conditions of engine oil. However, liquids under different brands can have many differences in chemical composition, and certainly in terms of additives. This circumstance may influence the appearance of a difficult-to-predict reaction during the mixing process, causing the appearance of sediment, which will simply create a blockage in the system. This is relevant for CVTs and automatic transmissions. The fact is that the design of the gearbox includes a filter. This part very quickly becomes clogged with reaction products, and the box itself breaks because its internal elements are poorly lubricated. Things are a little different with manual transmission. However, the consequences of mixing the oil will not be any easier.

Even experienced car enthusiasts sometimes believe that by mixing synthetics and mineral oil, you can get a liquid that resembles semi-synthetics in composition. And this is a very big misconception. First of all, when these liquids are mixed, foam will form, and after a couple of days of driving, sediment will appear. It was discussed earlier. After the car has traveled thousands of kilometers, the oil in the gearbox will become thick and clog the oil channels and other openings. Next, the oil seals may be squeezed out.

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Is it worth flushing the gearbox when changing gear oil: opinions of car owners

1. It's better to just warm it up. “There is no point in regular washing, unless during disassembly. In order for everything to be washed thoroughly, you need to drive several kilometers with kerosene. You understand that this is unrealistic. But you need to warm it up when changing the lubricant in the gearbox. Therefore, it is better to change the oil in the warm season – for example, in the summer.”
2. All parts are new as well.
   “I am the second owner of my VAZ-2104 car. Mileage about 100 thousand. The box started to leak, and I decided to take it apart. I drove about 50 km with an oil level of 500 ml when the norm is one and a half liters. I took it apart, and imagine my surprise when I saw that all the parts seemed to be new, without dust, dirt or whitish flakes. The previous owner said that he used Novoil once, then just topped it up about once a year. Accordingly, I decided for myself that flushing is not necessary, because the processes in the gearbox and the engine are completely different.”
3. The main thing is that the oil is good.
   “If good lubricant is poured in, then flushing does not need to be done. In general, it is recommended to carry it out every 30 thousand. And, by the way, when buying a new car, it is better to wash it after 5 thousand km. If you fill in a synthetic base from an official manufacturer, you can drive up to 60 thousand. And washing will only help remove metal particles from the gearbox.”

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4. It's better not to touch it while it's working.
   “I haven’t changed the lubricant from the factory for a long time. At 97,000 km I filled it with Castrol. No complaints so far, but it hasn't been winter yet. When they changed the old one, they found a lot of white flakes. The mechanic said to leave it as is while he works. In any case, washing residues will also remain. In the end, they just filled in with high-quality lubricant.”
5. It all depends on the situation.
   “If desired, you can use a ZIC brand wash, ideally leaving it on overnight. Its residues will not be as harmful as the mineral base. Of course, everything is individual in each situation. It is best to try to see what is inside the checkpoint. If the liquid is dirty and the walls are clean, everything is fine, you can use new oil as a flush. When surfaces are dirty, special washing is indispensable. If both the liquid and the surface are clean, don’t wash anything at all. And so, everything depends on the current circumstances.”