Update log: Feb 24th 2011: Based on number of comments, I'm recommending 3 quarts instead of 4. Read the note about it below if unsure.
Hope this is useful. Let me know if you find any errors and I'll fix 'er up. My car is a 2006 Mazda3 Sport wagon. I'm assuming the 5-speed tranny is the same on all North American Mazda3's but correct me if I'm wrong...
I couldn't find a write-up for this so I thought I'd do it myself. I'm reasonably happy with the shifts on my 3, but I notice some notchiness there at times. I decided to try Redline MT-90. I'm in Southern Ontario, and managed to find Johnston Research and Performance
in Mississauga as a retail seller of this oil. It's classified as a GL-4 and matches Mazda's requirement for a 75W90 oil. I'd read many good things about this oil in the past.
Usual disclaimer: These steps worked for me but double check your progress as you go. I can't be held responsible for any blah blah blah...
Things you'll need:
15/16" socket (mshu confirmed this is 23mm for the metric size) or wrench for the drain/fill plugs
Funnel and 3 feet of connecting tubing (recommended, you'll see I had some ghetto setup)
4 quarts Redline MT-90 UPDATE:
3 quarts Redline MT-90 or suitable synthetic 75W90 fluid (4 will cover you if you have any spills, the true capacity is 3.03 quarts) If you read the subsequent comments, most guys are more careful than me and needed only 3 quarts. Buy 4 if you're not sure if you can be spill-free.
Container that can hold at least 3 quarts
Usual tools for lifting the car and removing the plastic cover between the engine bay/underside of the front of the car (see any oil change write-up for these)
This was the first time I'd done anything to my Mazda3 (long time DIY mechanic on a old Nissan Maxima), so this was interesting for me.
I could see from the factory service manual and other reports that jacking up the car is easier if you drive it onto wooden blocks. I thought this was pretty incovenient, but I found out later that I could have done an oil change with the car just on the blocks.
Click any of the below images for a full size view - images are fairly large
I used the centre of the crossmember and put a piece of cardboard between my jack and the car body to prevent scratching.
I've had the dealer do the first couple of oil changes and could see from scuff marks from their lift, where I should put the jack stands.
After the vehicle was up on the stands, I removed the plastic shield that lies between the road and the engine bay (see any oil change guide on how to do this)
I realized I'd be best off with a level surface for the drain and fill, so I lowered the car back onto the planks. My garage is on a slight slope so it was probably level enough at this point.
Then I slid my waste pan under the drain hole (look at the top part of the image below, my screwdriver is pointing at it) and opened the bolt to start fluid flowing. The drain and fill holes are pretty easy to spot, they're the only bolts near the bottom of the tranny that are large (15/16", 23mm)
The fluid was a little slow to exit so I also opened up the fill hole (again shown by screwdriver) and then the fluid came out nice and quick.
Once the fluid had drained out, I replaced the drain plug. If you have an older car you may wish to replace the drain and fill plug gaskets. I've only had my car a few months and decided to skip this step.
Now for the interesting part. I would recommend buying a funnel with some 3 feet of tubing - it will make your life easy for the next part. In my case, it was almost a show-stopper until I found some regular copper piping normally used for residential plumbing. I had a funnel and 1 foot of flexible black tubing, but found it was not long enough. What you see in the next two images are the funnel, part of a turkey baster, copper tubing, and then on the underside of the car you can see the copper tubing going into flexible black tubing, finally going into the fill hole! Ghetto for sure, but it worked.
Take this step nice and slow, and put a clean container underneath. You'll need this near the end if you overfill, or in case you spill any (or if like me your crappy setup falls out). I found I used about 3.25 quarts, including a couple of spills. If you don't think you'll spill a drop, you may get away with 3, since the official capacity is 3.03 quarts in my owner's manual.
You know it's full when oil comes pouring back out of the tranny. Level with the fill hole counts as full - so if you've overfilled, allow fluid to come back out until it is reduced to the occasional drip, then replace the fill plug. At this point I gently moved the car through all the gears and waited ten minutes for things to settle. After that, it took a little more oil and then I called it a day.
I did not have a socket (I used an open-ended wrench) so was unable to torque down the drain and fill plugs accurately. I'll go back and do this later. The torque specs call for 29-43 ft-lbs in the factory service manual.
The shifting is noticeably easier, especially in the 1-2 shift which I used to find was quite notchy. To me, this was a worthwhile spend of about 60 dollars Canadian (inc. taxes), and would take the average person about an hour or two.