What engine oil do you recommend for mx5 mk3 40000 on clock
Mobil Super 3000 5W30 Fully Synthetic in mine.
Rightly or wrongly, when cold, I’ve got into the habit of flooring the accelerator pedal before turning the key to stop it firing for several revolutions to get the oil moving around. It seems to stop that initial metal-on-metal rattle when I then start it normally.
I’m running the same oil and would recommend as well. I tend to get it from Opie Oils or CMG Oils via eBay.
Sometimes there are deals on from either vendor; I think I paid nearer £30 for 5L earlier this year when I was servicing.
I don’t follow the same start-up procedure though, and don’t get any rattle! 
It’s the sort of noise you get from hydraulic tappets. Not biggy endy stuff .
I got my 5w 30 Mobil Super 3000 FE from Halfords and used the 8% club discount card.
It was the best price at the time above any online shops.
They have 10% off online purchases ATM but of course you can’t use your 8% club discount too (in-store only) factor in a delivery charge and it gets expensive that way.
Most all modern fully synthetic 5w30 oils will more than suffice.
Fuchs, Petronas to name but a few…
I tended to buy a 25 litre drum from the local motor factors and a six pack of suitable filters.
Keeps the cost down for me (but I do change both every 2500 miles with track and road use).
Another vote for mobil1 5w30 super3000fe 
. Seems fine so far for me, nc3 31k.