Mix Your Own Custom Diff Fluids

What do you do if you're filling your diffs and your LHS doesn't stock the exact differential fluid you need? Or what if you're in a hurry and you can't wait for the exact one you need to come in on order? Sure, you could make a substitution for whatever you might have on hand and put the right stuff in later, but let's face it, changing diff fluids isn't always easy or fun. So how do you do that when you don't have the exact kind you need on hand?

Short Answer:Use the “Fluid Blender” from GE Silicone: Click Here

If you're curious exactly how you're going to mix exactly 37% of 1K with exactly 63% of 3K to make 2K, then read on.

First you need to bookmark the above link. There is no amount of Google searching that will make that link surface (I tried for hours once). Next you need to round up the diff fluids you have and make a plan.

As you can see, I've got a little 1K, quite a bit of 3K, a little 5K and a little 10K. For my buggy, I want to use 5K, 7K and 2K. (You can see my problem.) Planning here is important. I could use 5K & 10K to make the 7K I need, but I need the 5K and I don't have a ton of it either. I do, however, have a lot of 3K and I can certainly make 7K out of 3K and 10K. Also, I don't have loads of 1K, but I don't have a choice. If I want to make 2K, I need to use 1K plus some other higher viscosity. I could use 5K or even 10K, but I don't really have loads of either of those so, I will use 3K along with 1K to make 2K.

Next, you need to figure out how much you want to make. I made 10ml because it made the math easy and I had a 10ml measuring thing as you'll see later. If you're curious, it seems to take about 5 cc or 5 ml to fill a diff. I have some 2K and 7K on order — I just need to get this buggy put back together in the mean time.

Next you need to run the numbers. Put in what you have and what you want to make and you'll get the results (handy little thing isn't it?):

Now it's time to mix. You need to find something that measures in ml, cc or something. I happened to have one of those little plastic spoons the pharmacy gives you when they give your kid antibiotics. I personally think the ideal tool for the job would be a syringe. You don't have to get medical though. Remember, you can use anything. Maybe you've got a 1/4 teaspoon measuring spoon. You could fill it up 7 times with 10K and 3 times with 3K and mix up some 7K in a bowl or something. (Just don't eat
it! lol). Anyway, here's a pic of me doing the mixing:

If you're using a tube like I am remember that you want to measure to the bottom of the bowl-shape the fluid makes at the surface (meniscus). Also, remember that if you get fluid on the side of your tube, you'll have to wait a good deal of time for the thick fluid to run down the sides to get a
good measure. With the first fluid, you have a little play. If you put too much in, you can stick something into the tube and pull out a little that clings to it as you remove it. With the second fluid, just add it to the first and just it in slowly until you get to the target amount. Go slowly, rushing this will only cause you grief when you add too much of the second fluid.

If you're lucky enough to have a syringe on hand, all you need to do is suck up X number of cc of fluid A and then Y number of cc of fluid B or until the syringe holds the target amount. Next you only have to squirt the combined fluid into your container and mix.

After you mix your fluids together (I used a chopstick to stir it), you need to find a container to hold the new mixture. I was lucky enough to find the two small diff fluid bottles to be empty when I was
done. Ironically enough, they hold exactly 10 cc each. The warning I have when you're doing this is to be sure and allow all of the old fluid to drain out of the container you're going to use. I put hung my spoon measure thing off a cup to let the 3k bottle drain for about 10 minutes.

Drinking Glass

Next, all that's left is to load the newly mixed fluid into the clean
container and mark it.
Mark It

I used a sharpie on these slippery plastic bottles. I just knew the ink wouldn't stay so I color coded the grooves in the plastic grip caps. Last night, we filled my son's center diff with the 7K and guess what? The letters “7K” rubbed right off as I figured. I'm gonna have to find a better way of marking them. Color coded lids works for now.

Anyway, I hope the next time you're in a bind for a certain diff fluid, you'll come back and check out this tip. 2K is only sold in the Mugen brand so a lot of people mix it this way anyway. It's not 100% super accurate, but it works like a charm when you're in need for a certain weight of oil in a hurry.