I hear what you guys are saying BUT when I bought the car it was serviced prior to delivery no idea what oil was put in it and generally when you get work done you are not allowed anywhere near the car (H&S) so it's on trust. So if they say fully synthetic its on trust. Same applies to all the previous oil changes/service done since 2004 on car by various dealers.

So I look at changing oil max 5,000 miles not 15,000 kilometers as suggested by Mobil and yes that makes for more expense but as I only do less than 5K miles per annum its done once a year (well will be if I keep car that long as it's one of 4) and the car itself has only averaged 5K miles per annum (has a total of 45,000 on clock)

(I tend to spend money on tyres as deficiencies in that area have potentially worse issues than a run bearing and an engine strip and build)

For interest I had a look at Mobil site too - it indicates for
Crossfire Mobil 1 New Life (?) 5.5 litres (???) 0W40 but again also suggests Mobil 1 ESP 5W30.
so had a look at MB SLK 3.2 NA Mobil 1 New Life (?) 8 litres (???) 0W40 and suggests Mobil 1 ESP 5W30.

They have reformulated Mobil 1 as I understand over the years good old Esso.

Halfords have it all on offer anyway



As they say you pays your money and make the choice