The crankshaft seal should be replaced when performing the major 100,000k interval service.
MAZDA JAPAN
1 Required per car.
Suits all NA6 Long Nose, NA8 and NB models
NOTE FOR 1.6L NA Owners
This seal is to suit the LONG NOSE crank which is found on 91 and on MX5's
It's hard to pinpoint the exact date of when Mazda switched to the long nose motor so it is best to look at the front harmonic balancer
4 notches (cutouts) in pulley = Short Nose
8 notches (cutouts) in pulley = Long Nose