Best Transmission Fluid For 4R100 (Type, Capacity, Guide)

One of the problems you may have is when you want to change the transmission fluid in this model of transmission. The dealers may not know which type you should use. Avoid Mercon LV at all costs according to most Ford experts.

The right transmission fluid to use in this transmission model is Mercon 5. Do not mix Mercon 5 with any other transmission fluid or you may cause damage to your transmission. This is an older transmission model and it is not made to handle Mercon LV.

To learn more about this issue, just continue to read our article. It has the information you want to know about. The 4R100 Ford transmission needs specific transmission fluid that is unmixed or you may be making more repairs than just changing the fluid.

What Transmission Fluid Does a Ford 4R100 Take?


The consensus is that you should only use automatic transmission fluid that is labeled Mercon V. It does not matter what brand is selling this fluid as long as the cans say Mercon V on it.

The word from a former Ford transmission engineer is that you should be wary of any compatible transmission fluids. Sometimes you will see the cans say Dexcron III/Mercon V on the label. That seems to be okay.

But according to that engineer, do not use Mecron LV or SP in this transmission model. This may cause some confusion as many of the review sites that list the top best transmission fluids for this transmission model list Mecron LV and other compatible options.

Another confusing bit of information is that the original owner’s manuals stated not to use Mercon V in this transmission. But When Ford stopped making Mercon, that was your only option.

Ford 4R100 Transmission Fluid Type


As you can see, there can be a lot of confusion about this topic. Right now, while Mercon V is still being made, and is still available, you should be using this type of transmission fluid. Of course, Ford limits the fluid to their brand only.

Other owners have stated that, as long as you are using Mercon V, the brand does not matter. Different owners have reported using other brand options with no problems. They also change their fluid every 40,000 miles.

The word is this restriction is designed just to boost the bottom line for Ford and their recommendation is not what is right for their customers. This seems to be the case as Ford banned Mecron V from the 4R100 until they stopped making Mecron. Now they say Mecron V is okay for this transmission model.

Best Transmission Fluid For 4R100


The best transmission fluid it seems will be Mercon V or compatible brands like Dexcon III/Mecron V options. While the Ford brand may be the best option to use, there are better brands out there that seem to do a great job.

Castrol is one, Amsoil is another, Chevron MD3 is still another good option and on it goes. You cannot always go by what the company or the manual says as there may be ulterior motives behind their recommendations.

If you are not sure which option to use, talk to a good transmission mechanic or two and see what they say. It is best to get a second, third, fourth, and possibly fifth opinion before making your decision.

If you go with Motorcraft, the Ford brand, then you are not doing anything wrong. But you may be paying a higher price than you should be for transmission fluid. Do comparison shopping as protecting your transmission is important.

Ford 4R100 Transmission Fluid Capacity


If you are only doing a drain and refill, then you only need about 6 1/2 to 7 1/2 quarts of transmission fluid. If you are doing a flush then you can expect to put 17 to 18 quarts inside the transmission system. It will depend on several factors on how much you actually use.

Just make sure you are using a Mecron V transmission fluid when you are doing this work. Avid the Mecron LV, ULV, & the SP as those are made for more modern transmissions and not for the older models.

These models are not quite there technologically speaking and more modern fluids should damage your transmission. Also, do not mix different fluid types together as that will not produce positive results.

Upgrades may make vehicles work better but they are harder to work on.

4R100 Transmission Fluid Change


This is one method and it should be followed after draining and replacing the fluid:

Disconnected the rear cooler line from the transmission, slid a 3/8" ID clear vinyl hose over the flange. Didn't need to clamp it since it was a good tight fit. Ran the hose to a bucket and used a small woodshop clamp to hold the hose in the bucket.

Started the engine and the fluid pumped into the bucket. When I saw air bubbles start, turned off the engine.

Measured the fluid pumped out.....5 quarts exactly.

Replaced 5 quarts, started engine, pumped out till bubbles.

Replaced 5 quarts, started engine, pumped out till bubbles.

Replaced 5 quarts, started engine, pumped out till bubbles.

Replaced 5 quarts, started the engine, moved the shifter through gears for a few minutes, checked the level, which looked like it needed about 1/2 quart, added 1/2, and then drove down the highway, came home checked the fluid level again, all is good and on the full mark.

I bought two cases of fluid, had 1-1/2 quarts left over, so I went through 22-1/2 quarts.” (source- scroll down).

Some Final Words

When it comes to transmission fluids, you need to make sure you get the right type. The brand won’t matter and because of that, you may save some money when you need to change your transmission fluid.

The key is to not use a lot of the newer transmission fluid options as they are not made for older transmissions. Even if the dealer says to use them, don’t. Protect your transmission at all costs.

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