what the oil capacity on the 1.5 gxi and what best grade oil to use as im getting a bit of knocking on cold start. all suggustion welcome.

It'll say in your owners manual, can't remember what it is tho

3.5-4 litres. Basically fill it until just below the full mark on the dipstick dipstick.

Same as above, i could not find it in the owners manual. Just keep on filling it on a flat surface until you reach near the the top of the markings of the dip stick

Think you'll be hard pushed to squeeze in the recommended 3.5 litres of 10w/40 fully synthetic with a new filter into a 1.5........

I have a job gettting 3.25 litres in her.

And for reference, Mazda use Castrol GTZ Magnetec 10/40W