Can you use 10w 40 oil in 05 Ford Fiesta?

Answer 1

Ford recommend 5w/30 oil for all their latest engines. Use of thicker oils will put a strain on the oil pump and, as the engine will have to work that little bit harder to move the oil, will cause increased fuel consumption.

A Google search on 5w/30 oils brings up some interesting facts - This oil is described as "fuel saving" (because it's thin) and another article points out that it's formulated to help keep catalytic converters working for many hundreds of thousands of miles, but the writer says that that is to the detriment of the valve train, as for the sake of the cat, the oil is low in the phosphates which help prevent wear. And in the UK, very few cars get up to 100,000 miles before they're scrapped. Here you must do your own research, as there are so many articles out there, some of which are contradictory!

My own choice of oil for my 1.4Tdci is 5w/40 fully synthetic. I would consider Mobil 1 0w/40 for Winter use as the "0w" indicates that it allows easy starting at lower temperatures - but I can't afford it!