In this cold weather, it is beneficial to use an oil that has good cold start flow properties as it will get to the parts of the engine that need it far more quickly.

The "w" number which means winter is the key here and the lower the better.

It may seem odd but a 15w or 20w will struggle to get around the engine in very cold temps and I would strongly recommend a 10w or better still a 5w for better cold start performance.

90% of all engine wear occurs on cold start because the oil get thicker the colder it is which causes engine wear.

These numbers explain what I mean and bear in mind that the oil will be the following thickness at 100degC (sae 40 = 14cst, sae 50 = 18cst and sae 60 = 24cst)

At 0degC these are the numbers (thick!)

Grade.................At 0C.........At 10C...........At 100C

0W/20.............328.6cSt......180.8cSt..........9cSt

5W/40.............811.4cSt......421.4cSt..........14cSt

10W/50............1039cSt.......538.9cSt..........18cSt

15W/50.............1376cSt.......674.7cSt.........18cSt

20W/50.............2305cSt.......1015cSt..........18cSt

If you are using anything more than a 10w oil, always warm the car properly before driving it as the oil needs time to circulate.

Just a word of warning really.