Keep your BMW. Use the extra £1000 to run it. Simple
That's about 3.5 months worth of petrol.....
-------------------------Petrol Diesel
Cost to buy------------ 0 1000
Miles Per Gallon (MPG)-- 27 40
Cost per litre----------- 100 103
Annual milage---------- 21000
Fuel cost per year------ 3531 2314
Fuel saving per year with diesel car 1217
Break even (years)----- 0.82