[color=blue]Hiya,
I believe the Mazda part number for your 1800 is:
B6Y1-14-302 9A @ £5.90 each, this is what the EPC disc says anyway, and if its anything like the 2000cc oil filter, then you would be better off with a genuine one as it has a non-return valve that helps to keep some of the oil in the engine, so it has a longer and happier life, and for 6 bucks you can't grumble at the price!!
Know what you mean with oil filters from Halfords, my Galant's filter was a good inch smaller in diameter then the Halfords one!! Still fitted though.....

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