10w30 is recommended by Ford for these engines in NA form. Once you add a turbo and some boost oil temp will be a little higher, that's why ford recommends a w40 oil and you should stick with it. If you do anything that will cause oil to be heated any further like track work, serious hill climbs, heavy towing you can maybe go up to w50, w60 would only be for extreme situations. Remember that ford built an engine oil temperature warning light in to these things and only few have ever seen the thing come on so they can't be getting that hot to require a w60 oil.