Jacked the passenger side of the car up today until my little spirit level placed on the "flange" (which is not absolutely flat, there's a casting "edge" on it) indicated that the box was level. There was a slight see saw action on the spirit level due to the aforementioned casting "edge" but it resulted in only half a bubble either side of the spirit level centre line and so was considered "level". I removed the fill plug, i had already ascertained that the oil level was upto the fill plug whilst the car was parked on leve ground.
I topped up the gearbox oil whilst it was "level" (car jacked up) and was able to get 270ml additional fluid into the box at which point it overflowed. I've left it at that level. I originally put in 2 US quarts of Redline 75 90 equating to 1.892 litres when the car was on level ground. Gearbox capacity to filler plug leve would appear to be 2.162 litres or there abouts.
Did you happen to measure how far it was jacked up to save using level in the future, as that may be useful for others.
I struggled to find a suitable location for the level so merely increased height by 2 inches by driving onto a length of 7 x 2. That resulted in just an extra 150 ml going in. I note from your experience that you now have a little over the 2 litres that Mazda specify. I guess if it is a lot over, then seepage could occur through external shafts? worth keeping an eye on it especially when moving the car after a longer period of rest.
