NC MX-5 Miata (2006-2015) Oil / Trans / Diff Fluid Change

Ready for some maintenance!

Ready for some maintenance!

Howdy NC Miata (or MX-5, whichever you prefer) owner!! Got a new-to-you car and want to do some maintenance? I found myself in that situation not long ago. I had to hunt all over the net for fluid and torque specs and then find out where everything went.

This is my attempt to put it all in one place to help you.

Step 0: Put the car securely on jack stands. And use the best jack stands you can find. Years ago, I did a multipart blog post about different jack stand types. Check it out if your stands are getting a bit old.

I feel perfectly safe laying under my car and having my little girl laying next to me. Can you claim that about your jack stands?

NC MX-5 Oil Change

NC Miata oil and filter.

NC Miata oil and filter.

What you need:

  • Oil – The factory calls for 5w20 oil and the engine takes 4.9 quarts when dry. You will need somewhat less than 4.9 quarts.
  • A filter – I’m a fan of Purolator, Mobil1, and Wix. The parts store had none of these, so I’ve got a Bosch in the pic.
  • A new crush washer. You need one for an M14 bolt. So 14.2mm inside diameter, 20mm outside diameter.
  • Used oil containment – I’ve got a pic coming in a moment. Recycle your used oil!
  • Wrenches, paper towels, rags, gloves, and any other stuff you usually use.
  • The previously-mentioned jack stands. Ramps or a lift work too.
Oil Drain Plug location.

Oil Drain Plug location.

The drain plug is about where you’d expect it. Roughly the center of the car under the engine. In the photo above, the car’s nose is to the right and the driver’s side (US LHD) tire is visible in the lower right.

There’s a protective metal belly pan, but it doesn’t need to be removed for the oil to come out. No oil got on mine when I changed it this way.

The filter is another matter…

Oil filter location.

Oil filter location.

The filter is rather hidden. If you lay under the car near the driver’s seat (again, left hand drive), you can see it when looking toward the nose of the car.

It’s also got lots of metal under it and the oil gushes free when you remove the filter. I learned this after my NC’s undercarriage was coated in oil. I would highly suggest some kind of small oil containment device like a cut-down milk carton. Something short but wide that can fit between the filter and the metal bits.

View from the wheel well.

View from the wheel well.

It’s much easier to remove the front left tire than to struggle with the filter underneath the car. There’s a lot of room to get the filter out with the tire removed. I used my ancient filter wrench and had no problems freeing the filter.

Out comes the black stuff.

Out comes the black stuff.

  1. Remove oil filler cap on the top of the engine.
  2. Remove oil drain plug. You need either a 17mm socket or a 19mm socket for this.
  3. Drain the oil. It’s always nice to do this with a warm engine. Let the oil drain as long as you like.
  4. Put a new crush washer on your drain plug and install it back in the sump. Torque the drain plug to 23-30 ft/lbs.
  5. Deal with the oil filter. Get it out and try to keep the mess to a minimum.
  6. Pre-oil your new filter with some fresh stuff and install it on the engine.
  7. Add oil to your engine. It’ll take somewhat more than 4 quarts. Reinstall the cap.
  8. Start engine and verify oil pressure. Turn it off, let oil drain back into the pan and read the dip stick. Add more oil to get it up to full.
Oil containment.

Oil containment.

I bought this fancy oil container at the local O’Reilly’s last year. It’s enormous and can take something like 16 quarts of oil. It stands on the end so it doesn’t take up a lot of space. It has special spots to let many different kinds of filter drain. And it has really nice caps to prevent leaks.

I highly recommend something like this. It makes oil transport and recycling a breeze.

And that’s all there is to an NC oil change. Very simple stuff.

NC Miata Transmission Fluid Change (MT)

Transmission Fluid Change

Transmission Fluid Change

What you need:

  • Oil – You need a GL-4 75w90 fluid. The Motorcraft stuff (also known as XT-M5-QS) gets rave reviews. I used it in mine. You’ll need 2.2 quarts.
  • A fluid pump. Dear NC owner, please invest in a nice fluid pump and a lot of hose to fit it.
  • A new pair of crush washers for a M18 bolt. The fill and drain plug take the same size.
  • Used oil containment.
  • Wrenches, paper towels, rags, gloves. I believe both plugs are 24mm.
  • Four jack stands to get the car up and level. Or a lift.

This is not a hard job. You can make it hard if you don’t have a nice fluid pump. But this should not take you very long with a decent fluid transportation device.

Remove the fill plug first.

Remove the fill plug first.



Remove the fill plug first.
I’ve read horror stories on the internet of guys getting their cars in the air and transmissions drained only to find that the fill plug was pretty much welded to the case. Do not let that be you. Work on the fill plug first. Once you get it off, then remove the drain plug and drain the trans lube.

Both plugs are easily accessible. Both take an 18mm crush washer. Both used the same socket, which I believe was a 24mm.

Oil drain plug.

Oil drain plug.

Yuck.

The drain plug is magnetic and will (hopefully) trap metal bits. Mine was pretty much coated. I snapped this with my left hand because I didn’t wanna touch my camera with the oily right one. ha!

Clean off the drain plug and reinstall it. Torque the drain plug to 29-42 ft/lbs.

Insert the fill hose into the side of your tranny and weave it up to the engine.

Pump!

Pump!

This is where a nice fluid pump saves the day. Would you rather lay under the car with a tiny hand pump on your chest? Or would you like to stand comfortably and fill the transmission without getting crap in your eyes?

Yeah. Me too. It’s nice to stand and pump fluid.

You’ll be left with roughly .8 of a quart once you’re done. Fill until the fluid comes out the fill hole and then cap it up. Nothing else to it. Torque the fill plug to 19-28 ft/lbs.

If you want to grease the shifter turret, you’ll be using some of that extra transmission oil in just a few minutes…

NC Miata Differential Fluid Change

Diff fluid.

Diff fluid.

What you need:

  • Oil – You need a GL-5 75w90 fluid. I’m a huge Redline fan. You’ll need just under 1 quart.
  • A fluid pump.
  • A new pair of crush washers for a M18 bolt. The fill and drain plug take the same size.
  • Used oil containment.
  • Wrenches, paper towels, rags, gloves. I believe both plugs are 24mm.
  • Four jack stands to get the car up and level. Or a lift.
Diff fill and drain plugs.

Diff fill and drain plugs.

This is roughly the exact same job as changing the transmission fluid. The diff uses less fluid, but I could not figure out a way to add fluid from on top. There’s no good drain plug in my NC’s trunk. That means laying under the car and pumping fluid. Ugh.

Remove the fill plug first. It needs a 23mm socket. Don’t be that guy who can’t get the fill plug off and doesn’t have any lube left in his diff!

Remove the drain plug next. It needs a 24mm socket as I recall. Let the fluid drain out. Don’t get any on your shirt because GL-5 gear oil is smelly stuff.

Once the fluid is out, install a new 18mm crush washer and torque the drain plug to 29-39 ft/lbs. Then pump in the new fluid. Once you’ve got most of the quart empty and fluid is coming out the fill hole, torque the fill plug to the same spec, 29-39 ft-lbs.

Remove the jack stands and drive the car around in glory. Nothing like the after-maintenance test drive to give you a sense of accomplishment. Well done!

NC Miata Shifter Turret Grease (MT)

There’s some discussion on miata.net as to whether this is needed or not. One camp seems to believe that the turret greases itself. The old guys who had NA and NB cars believe it needs lube.

I don’t wanna cause a debate. I’m just here to show you how to lube the shifter turret if you so desire.

Remove the change tray.

Remove the change tray.

You have to remove the NC armrest / center console. Compared to the NA or NB this is a bear. Lots of plastic clips and chances to break stuff. But if you go slow, you can do it.

I used a rigid putty knife to pry out the change tray. I’ve read of folks using a razor blade, but that seems hazardous to eyes. No matter what you use, be careful. Pry on the front edge and slowly work around to get all the clips popped free. It will hinge up as shown in the photo above.

There’s 2 screws under the change tray.

Cup holder screw.

Cup holder screw.

The center screw is under the cup holder base. Just pry that little black plastic piece free and get access to the screw. This is the easiest one to access.

Mine had mold underneath. It was horrible. Wear gloves and decontaminate your NC interior if required.

Rear cover removal.

Rear cover removal.

This seemed like the most complex piece, but it was very easy to remove. Insert a pry tool at the edge shown and pop it free. Then work your fingers under the sides to remove the rest of the cover.

There’s 2 more screws under that rear piece. Once those are gone, you’re in the green.

You also need to remove the shift knob (it unscrews) and the hand brake boot. I didn’t take photos of these. They’re quite easy to remove. The brake boot is held in by a plastic ring that just pops free with the slightest bit of pressure.

Upper shift boot.

Upper shift boot.

Remove the upper shift boot. It has 4 nuts holding it in place. A deep 10mm socket does the job.

Underneath this boot is a stick-on rubber boot. Like a dust cover or noise barrier. It just peels off.

Lower shift boot.

Lower shift boot.

The lower shift boot is held on by 3 bolts. Remove them. Note the orientation of the shifter, lower plastic ring, and boot as you remove the stick itself.

Have a towel ready to lay the shifter on. If yours still has fluid in it, you don’t wanna get said fluid on your car’s carpet.

So empty.

So empty.

After 156,000 miles, The Stormtrooper’s shifter turret was totally dry. No lube anywhere. Nothing was even slightly wet.

No wonder the car randomly couldn’t go into 1st gear…

Nice and wet.

Nice and wet.

The shifter turret takes 80-230cc of GL4 gear lube depending on how much fluid is in there. Mine took the full amount.

You should also grease the top of the shifter above the ball as it is a friction point. Internet wisdom says “use grease.” I had some black moly handy. I’m not sure if that was the right one, but I put a thin film on the top of the ball and reinstalled all of the parts.

After this maintenance shifting was a night and day improvement. The notchy, sticky shifter went away and I was left with a precise Miata shifter similar to any NA or NB I’ve ever driven. I’ve not been locked out of first gear since doing this maintenance either.

Success? I think so.

I hope this guide helps some folks out. And if I’ve forgotten anything or messed up any fluid specs, please leave a note below.

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  • Jason says:

    Nice explanations. As neither a Miata owner nor a “car guy”, I’m likely an outlier in terms of your usual visitors. But I’m certainly a Maker and I find reading your site and your explanations fascinating and informative. Enjoyable reads and great photos as always. 🙂

  • Brad says:

    That upper shift boot does wonders at keeping both heat and noise from the transmission out of the cabin. Drove the Supra around without the upper boot on for a few days as I was putting the interior back together, and wow, what a difference that boot makes.

    Also, I absolutely stand behind the advice to always, 100% of the time, remove the fill plug first. I’ve been “that guy” who nearly couldn’t drive his car because he couldn’t get fluid back into the transmission or diff. Don’t be that guy.

    On that note, for the love of all that is holy, do not use a 12-point socket or wrench on large 6-point bolts like the fill and drain plugs. Doing so will increase the chance that you’ll round off the plug. Six point bolt head, six point socket. Those sockets may prove a bit difficult to find, depending on where you are, but trust me on this one folks… do it right.

  • david says:

    Well done!
    concise and great photos in support.
    Question: will filling the turret serve to overfill the trañny?
    Would it be better to fill the turret and after doing so
    replace the fill plug?
    Im using the motorcraft lube to replace the lucas which
    gave notchý first gear and at times second gear engagement.
    Thanks

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