I have 10 litres of Castrol Edge 0w30 FST A5/B5 in my shed.

As far as I'm concerned compared to the 5w30 WSS-M2C-913C that my car is designed to have it will have better flow characteristics when the engine is cold and will behave like a standard SAE 30 oil when up to temperature.

It was purchased for my Mondeo as I was running it on 0w30 as it took a while to get upto temperature once the EGR was removed and I fully plan on running my Focus on 0w30 oil once it's out of warranty.

BUT...
Do you think the dealer would see it in the same way I do? My car is due it's first service and I thought I could save some money by supplying the oil.

Or is it not worth the risk while it's under warranty?