Transmission fluids have several main purposes they must fulfill in a transmission. These purposes include:
- Wear protection
- Heat dissipation
- Foam prevention
- Hydraulic force transmission
- Shift quality
- Compatibility with materials.
Organic and synthetic oils react to each of these differently.
Lubrication: Temperature is a large factor in the proper lubrication of a transmission fluid. Organic transmission fluids grow more viscous in colder temperatures, and the change in temperature changes the properties of the fluid. Synthetic fluids handle the temperature change with less reaction, making them more thermally stable.
Wear Protection:A fluid’s ability to protect against wear depends on the temperature and the additives in the oil. Organic fluids already suffer from temperature variations, and so must have more additives to help prevent wear on the transmission. Synthetic oils are more stable. Which type works better depends on the requirements of the vehicle, but synthetic oil in general will prevail.
Heat Dissipation:Once again, organic oils react more strongly to temperatures. Organic oil will thin out and eventually reach a flash point at a high enough temperature. A mixture of oil and vapor is much less effective and dissipating heat. Synthetics have a much higher flash point, making them better at heat transfer.
Foam Prevention:The creation of foam in transmission fluid severely hampers the ability it has to do its job. Air bubbles can compress, and the hydraulic transmission of force is reduced when this happens. Both organic and synthetic transmission fluids have the same range of anti-foaming agents added, preventing them from foaming while in use.
Hydraulic Force Transmission:Hydraulics works with fluids because fluids do not compress like air compresses. A simple hydraulic device, a pipe filled with a liquid, will transfer virtually all of a force applied to one end through the liquid to the other end, as long as no leaks allow compression. At normal temperatures, both organic and synthetic oils will not compress, allowing the same degree of force transmission. When an oil begins to flash to vapor, it becomes a gas, which is compressible. This compression weakens the ability of the oil to transmit force. Thus, at higher temperatures, a synthetic fluid will operate more effectively for longer.
Shift Quality:How a transmission shifts is dependent on the level of friction allowing the gears to clutch each other and engage. Too little friction and the gears will have a hard time engaging, making shifting harder. Too much friction causes wear on the entire system, damaging it over time. Neither organic nor synthetic oil has an advantage in shift quality, because each vehicle specifies its own required level of friction.
Compatibility with Materials:A transmission fluid must not interact negatively with the gaskets, o-rings and other components of a transmission. If an additive is reactive with the material of a component, that component will be damaged through exposure tot he additive. That said, transmission design is standard, and the reactivity of additives is tested and ensured to remain minimal. Both organic and synthetic oils are identical in this regard.
Pricing Comparison: While it seems like synthetic transmission fluids are a clearly better option, they have the single drawback of being more expensive to purchase and replace. The current cost for synthetic vs. mineral oil change can be found on our Facebook page. We are a Transmission repair shop in Mississauga.
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