What is Transmission Fluid and What Does it Do?

Transmission fluid is used to lubricate the components of a car’s transmission for optimum performance. In vehicles with automatic transmissions, this fluid also acts as a coolant. There are several types of auto transmission fluids, and the type used in individual cars and trucks depends on the type of transmission inside. Automatic transmissions use regular automatic transmission fluid, as the name suggests. Manual transmission fluid can vary, however, using either plain motor oil, a transmission oil known as heavyweight hypoid gear oil, or automatic transmission fluid. The type of transmission fluid to use in vehicles with standard transmissions can usually be found in the maintenance section of the owner’s manual.

While the primary function of auto transmission fluid is to lubricate the various parts of the transmission, it can serve other functions as well:

  • Clean and protect metal surfaces from wear
  • Condition gaskets
  • Enhance cooling function and reduce high operating temperatures
  • Increase rotational speed and temperature range

Different types of transmission fluid

There are also a myriad of different types of transmission fluid that go beyond merely dividing between automatic and manual transmissions. To achieve the best performance under high temperatures and extend the fluid’s life fully, use the transmission oil or fluid variety recommended by your vehicle’s manufacturer, which is usually found in the owner’s manual:

  • Dexron/Mercon: These varieties, available in different quality grades, are the most commonly used automatic transmission fluids today and contain friction modifiers to best protect the internal surfaces of the transmission.

  • HFM Fluids: Highly Friction Modified (HFM) fluids are much like Dexron and Mercon types, but the friction modifiers in them are even more effective.

  • Synthetic Fluids: These types of fluids often cost more than Dexron or Mercon, but they are designed to better withstand drastic temperature changes and greatly reduce friction, oxidation, and shearing.

  • Type-F: This type of automatic transmission fluid is used almost exclusively in vintage 70s model vehicles and does not contain friction modifiers.

  • Hypoid Gear Oil: Used in certain manual transmissions, this type of transmission oil is highly resistant to extreme pressures and temperatures.

  • Motor Oil: Although motor oil is usually used in a vehicle’s engine, it works in a pinch to lubricate manual transmissions because it has a similar composition and properties to that of gear oil.

Depending on the type of vehicle you own and the length of ownership, you may never have to worry about the type of transmission fluid you use. That’s because it’s not necessary to change it frequently. In fact, some automatic transmissions may never require the fluid to be changed, although most mechanics recommend changing it every 60,000 to 100,000 miles. Manual transmissions require more frequent transmission oil changes, usually every 30,000 to 60,000 miles. If you are in doubt of whether your vehicle needs fresh transmission fluid or oil and what type to use, don’t hesitate to consult with one of our experienced mechanics.


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Recent Transmission Fluid Service reviews

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1,126
43
10
7
15

Greg

22 years of experience
155 reviews
Greg
22 years of experience
Honda Accord L4-2.4L - Transmission Fluid Service - Scottsdale, Arizona
Greg was very helpful, friendly, and extremely detail oriented. At the end of the service, we went through everything he had done with my vehicle with the many pictures he took, and gave me some information of recommended services that should be on the horizon. 10/10 would recommend.
Honda Ridgeline - Transmission Fluid Service - Mesa, Arizona
Very good experience. Greg went above and beyond, extremely professional and great customer service.

JOHNNY

33 years of experience
140 reviews
JOHNNY
33 years of experience
Volkswagen Jetta L4-2.0L Turbo Diesel - Transmission Fluid Service - Folsom, California
Second time I used this service with the same mechanic He is as good as it gets On time, friendly, fast and clean. I would love to get him again for my next service need Highly recommend
Acura TL - Transmission Fluid Service - Sacramento, California
This is my second time using Mr. Johnny and he was on time and completed the job in under 2 hours. It was another great experience. Thanks!

Kenneth

20 years of experience
697 reviews
Kenneth
20 years of experience
Toyota RAV4 L4-2.5L - Transmission Fluid Service - Torrance, California
Kenneth is professional, timely and seems very knowledgeable. He has a good work ethic. Thanks Kenneth!
Jeep Wrangler - Transmission Fluid Service - Long Beach, California
Polite, courteous & very informative. Gets the job done in record time. Couldn’t be more pleased with the service.

Peter

25 years of experience
457 reviews
Peter
25 years of experience
Audi A8 Quattro V8-4.2L - Transmission Fluid Service - Canyon Country, California
Showed up on time, completed job n a timely manner and shared his knowledge and history of service/repairs on my vehicle.
Honda Odyssey - Transmission Fluid Service - Sylmar, California
Peter is such a nice person with an amazing attitude. We would love to have him as our regular mechanic.

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