I wouldn't go near any belts with WD40 if that is what you think your problem is. It contains petroleum products that will degrade your rubber AND cause slippage. There is a readily available spray on belt-grip that works well. Are you sure it's not your starter motor Bendix gear being a bit sticky to retract from the flywheel ring-gear in cold conditions?? That will whirrr and grind immediately after a start. By the time you get the car to Mazda it will be hard to reproduce the noise when it is warm. Just a thought.....
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