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Welcome to Americas #1 Trusted Oil Website

Largest and most knowledgeable AMSOIL Group in the U.S. and Canada led by the only AMSOIL Regency Platinum 7 Star Direct Jobber in the Organization who is also a former Ford Motor Company Senior Powertrain and Chassis Engineer. We also have a General Motors Engineer in our Group and will utilize our collective expertise and experience in order to provide you with the most up to date product and technical recommendations and we will accurately answer all your detailed vehicle related questions.

The Automatic Transmission

The hydraulic fluid used in automatic transmissions is a very specialized fluid because it is required to do a lot more than just lubricate. It is subjected to very severe service and is one of the most complex fluids used in an automotive system. The primary functions of an automatic transmission fluid (ATF) are:

1. To transfer power from the engine to the driveline via the torque converter.
2. To absorb and transmit heat from the torque converter to the cooler located in the front of the vehicle and to act as a clutch pack friction element coolant. It must absorb and dissipate the heat energy dissipated by a clutch or band engagement.
3. To transmit hydraulic pressure through a complex hydraulic control system which uses valves, servos, pumps, clutch cylinders and fluid lines and passages.
4. To act as a lubricant and coolant for the planetary gears, bearings, servos, clutches and bushings. 

An ATF can be subject to extremely high temperatures during engagement of clutch plates and this must be absorbed and dissipated effectively. If the transmission fluid cannot withstand the heat it will oxidize and can result in destroyed friction materials, sticking valves and servos and plugged passages and filters. An ATF must also have high resistance to varnish and sludge build-up that results from high heat generated in the torque converter. It must also reduce wear and corrosion, prevent foaming and act as a sealant and control the quality (shift feel) of the clutch and band engagement. It must be fully compatible with the materials used in within the transmission such as seal materials and friction plates. An ATF must also be able to maintain a stable viscosity throughout a wide range of operating conditions and temperatures. At low temperatures it must be “thin” enough to be able to flow for proper cold weather shifting but not so “thin” that it cannot effectively operate the pumps, pistons and servos in order to maintain proper hydraulic pressures at high operating temperatures.

This is a simplified overview intended to demonstrate the complexity required of an automatic transmission fluid. It is not my intention to cover the intricacies of how an automatic transmission functions or the specific details of base stocks chemicals and additives engineered into an ATF.

There are three main types of ATF in use today for cars and light trucks: The GM Dexron II and III, Ford Mercon and Mercon V and Chrysler ATF+ thru ATF+4. There are some other automotive manufacturers, such as specific newer models and years of Honda vehicles, which have their own ATF that is specified to be used, although they do state that in a situation where Honda fluid is not available that GM Dexron III is acceptable for short term use only. Most other automotive manufacturers accept fluids that fall into one of the three main categories above and perform extensive testing to ensure that the fluids are fully compatible with their transmission designs. There is also an Allison C-3 and C-4 and a Caterpillar TO-2, TO-3 and TO-4 fluid, which are commonly used in heavy truck and heavy diesel off road equipment.

Most common petroleum ATF’s are specified to be changed at approximately 15,000 to 30,000 mile intervals. Many automotive manufacturers have recognized the need for superior transmission fluids that can withstand severe operating conditions for longer periods of time and now there are some manufacturers that specify 50,000 mile changes or even 100,000 mile changes under normal operating conditions. Towing heavy trailers, hauling heavy loads, stop and go driving and/or other severe operating conditions can significantly reduce these recommend normal service intervals. These extended drain interval specified fluids are either a synthetic or a semi-synthetic blend. The automatic transmissions on passenger cars and light trucks are typically one of the most neglected service items. The extended drain intervals specified on many newer vehicles are the manufacturers response to address these issues, however I must stress again that these recommended extended service intervals are for normal operating conditions.


The semi-synthetic blends are typically a petroleum ATF with 10-20% PAO’s added to the fluid. The PAO’s lowers the temperature at which the fluid forms a wax gel but the other advantages that accompany the small amount of PAO such as improved oxidation resistance or flash points are small or negligible.

I have also seen some newer vehicles that have no ATF filler tube. At 100,000 miles (based on normal service conditions) the vehicle is supposed to be taken into the dealership and have the fluid pumped out using a special fluid exchange machine. The machine will pump all the old ATF out and pump the new fluid in with an efficiency in the 98-99+% range, meaning these machines are highly effective in getting the old fluid out and the new fluid in. I also recommend these machines for anyone that is changing their fluid from a petroleum ATF to a premium quality synthetic ATF. The cost to pay to have this service performed is very nominal and will save you a lot of time and headaches than if you try to do the job yourself. You cannot get enough fluid out by simply doing a pan drain and refill. You’ll still have a lot of old fluid in the torque converter, valve body, pumps, lines and cooler. Just make sure you take it to a reputable and qualified service center and that the premium quality synthetic you bring them actually is put in the vehicle.  

Also, it is a good idea to have a new filter installed at this time so you know exactly when it was changed. Normally, ATF filters do not need changing very often. I personally install the new filter when I install the synthetic ATF and then I will not change again it unless something in the oil analysis test results indicate it is necessary to change the filter or the fluid. I also install remote ATF fluid filters under-hood on my vehicles, which adds an increased measure of filtration protection as well as makes it very quick and easy to service the filter.  

I highly recommend using a premium quality synthetic ATF vs. a petroleum ATF or a semi-synthetic blend. The benefits of using a premium quality synthetic lubricant include significantly lower operating temperatures. Heat is the killer of automatic transmissions. I have measured these differences with transmissions that have been instrumented with thermocouples and specialized recording equipment, however it is also dependent on the vehicle operating and load conditions. A premium quality synthetic ATF will also provide exceptional resistance to oxidation and thermal degradation and maintain a very stable high temperature viscosity. Low temperature performance is excellent as well as significantly improved anti-wear performance along with extended drain intervals in the range of three times longer than petroleum oil under severe service conditions or up to approximately five times longer under normal operating conditions. As previously stated with engine oils I also recommend performing periodic oil analysis testing on your synthetic ATF in order to get an accurate reading of how well it is performing and when it may need to be changed.

As I have previously mentioned and will explain again due to its importance is that synthetic ATF is not more “slippery” than petroleum ATF. The base fluids, whether or not petroleum oil or synthetic oil, play no direct role in the relative friction levels of wet clutches. The friction-modifying additives developed for petroleum oils work just as expected in synthetic PAO fluids. The longer the fluid resists oxidation, the longer the original frictional properties remain. The superior oxidative stability demonstrated for synthetic ATF’s thereby leads to extended retention of frictional properties.

There is also one manufacturers brand of premium quality synthetic ATF (AMSOIL INC.), which covers all major domestic and foreign manufacturers specifications with one fluid. This is the only fluid of this type that I am aware of that is available. It is a highly complex fluid formulation and to date no other manufacturer has been able to formulate a similar type of ATF. It is also one of the company’s most highly guarded trade secrets. Although the fluid is specified to cover all applications, it is tested independently to the exact specifications of each manufacturer.

AMSOIL ATF Maximizes Automatic Transmission Efficiency and Life

Over 40 percent of total energy loss in an automatic transmission can be attributed to the act of pumping automatic transmission fluid to the transmission's working components during transfer of power. The mechanical efficiency of an automatic transmission is directly affected by the viscosity of the transmission fluid. When temperatures drop and cause ATF to thicken, transmission efficiency and power decline. Industry tests on torque loss demonstrate that a temperature increase of 150 degrees F increases transmission efficiency by up to 37.5 percent. In other words, as viscosity decreases, transmission efficiency increases.


Higher quality automatic transmission fluids can have a profound impact on transmission efficiency. Automatic transmission fluids with lower cold temperature pump ability properties effectively keep transmissions running efficiently during cold weather, maximizing both transmission power and fuel economy. 

The Brookfield Viscosity Test gauges a transmission fluid's viscosity in cold temperature conditions. Current industry specifications dictate that Brookfield Viscosity not exceed 20,000 cP. While the average conventional transmission fluid has a Brookfield Viscosity of 15,000 cP, AMSOIL Synthetic Transmission Fluid far exceeds the minimum standard with a Brookfield Viscosity of 7,454 cP, ensuring maximum transmission efficiency and power even in the coldest winter temperatures.  

AMSOIL Synthetic Automatic Transmission Fluid exhibits outstanding oxidation stability, preventing viscosity increase that leads to reduced transmission efficiency and cold temperature performance.  

While the use of AMSOIL ATF ensures maximum transmission efficiency, its shear stability and premium anti-wear additives also ensure superior wear protection, exceeding industry standards in the Four-Ball Wear Test, FZG Test, Vickers Wear Test and Falex Extreme Pressure Test (see test results below).

ASTM Wear Test:
 Four-Ball Wear Test (ASTM D-4172B), 100°C and 150°C Average, 600 RPM, 40 KG, 2 hr. Performance Standards: Mercon V: 0.61 max. AMSOIL Performance: 0.38

ASTM Wear Test:
 FZG ASTM Test Performance Standards: Mercon V: 11 min. AMSOIL Performance: 12 

ASTM Wear Test:
 Vickers Wear Test (ASTM D-2882 Mod) Performance Standard: Mercon V: 10.0 max AMSOIL Performance: 2.8 Performance Standard: DEXRON III: 10.0 max AMSOIL Performance: 2.8 

ASTM Wear Test: Falex Extreme Pressure Test (ASTM D-3233) Performance Standard: Mercon V: 750 lbs. AMSOIL Performance: 1500 

ASTM Oxidation Tests Aluminum Beaker Oxidation TEST (ABOT) % viscosity increase 40°C 300 hrs Performance Standard: Mercon V: 25.0 max AMSOIL Performance: 0.03


General Motors 700r4, 4l60e, 4l65e Exploded View.


Ford e4od, 4r100 Transmission

AMSOIL is the undisputed leader in synthetics.............  

When you compare....there is simply no comparison. AMSOIL is the best motor oil!

AMSOIL Satisfies the Demands of Modern Automatic Transmissions  

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