Can Transmission Fluid Be Used as Power Steering Fluid?

[DiCorey]

Power steering fluid and transmission fluid absolutely cannot be used interchangeably, as they are two products with different properties. Here is a detailed explanation: 1. The main function of transmission fluid is to keep the gear system clean, and to lubricate and prolong the life of the transmission device. 2. Due to different transmission designs, they are divided into manual transmissions and automatic transmissions (which are further divided into CVT, AMT, etc.). Each transmission design has different technical requirements. Even the same model of transmission configured in different vehicle models will have differences in torque, weight, speed, structure, etc. Therefore, the original manufacturer has its own specified dedicated transmission fluid. 3. Power steering is a new technology in automobiles that increases comfort, automatically providing steering force when the driver turns the steering wheel, thereby reducing the driver's steering labor intensity. Power steering fluid is a medium oil filled in the power steering system, which plays the role of transmitting steering force and buffering.

[Remington]

I'm an experienced auto repair technician and have encountered this issue many times. Absolutely not! While transmission fluid and power steering fluid may both look like hydraulic oils, their formulations are completely different. Power steering fluid must withstand high-temperature, high-pressure environments while maintaining fluidity to protect seals. The additives in transmission fluid can react with rubber components in the power steering pump, causing seal swelling and deformation over time. Last month, an old Buick Regal owner mixed these two fluids, and after just 200 kilometers, the steering wheel became completely stiff, eventually requiring replacement of the entire power steering pump. Remember: only use fluids labeled ATF or PSF on the power steering reservoir cap. Transmission fluid belongs strictly in the transmission.

[Albuquerque]

As a veteran driver with over twenty years of experience, I've personally learned the hard way about mixing fluids. Once during a long trip, I found the power steering fluid had completely leaked out, so I temporarily topped it up with some automatic transmission fluid as a stopgap. The next day, turning the steering wheel felt like bending an iron rod. When the mechanic opened up the power steering pump, all the rubber seals inside were swollen. Nowadays, most new cars use electric power steering and don't require fluid changes, but owners of older vehicles using ATF hydraulic fluid should take note: transmission fluid is too viscous and flows too slowly, causing delayed steering response. The key issue is that some transmission fluids contain friction modifiers, which can actually accelerate wear on the copper components inside the power steering pump, leading to repair costs upwards of two thousand yuan.

[Larry]

Last weekend, I witnessed an accident case at the auto parts market. The repair shop owner pointed at a towed-in Focus and said: The owner poured CVT transmission fluid into the power steering reservoir, and after driving just thirty kilometers, the steering wheel locked up. Upon disassembly, it was found that the power steering pump rotor and liner had seized, with the oil passages completely clogged with gum deposits. The manufacturer's technical manual clearly states that the steering system operating pressure can exceed 100 bar, requiring the use of specialized fluid with good low-temperature flow properties. Mixing fluids can lead to overheating and failure of the power steering pump, with the cost of a new assembly plus labor exceeding 1500 yuan—totally not worth it.