Using MOBIL 1 OIL, 5W 40 instead SLK230 2001

I live in Nashville Tennessee USA and my mechanic recommended using 5W 40 Mobil 1 synthetic instead of 0W 40 which is the manufacturer's recommendation. My car has 58K miles. Since the 0W is for sub zero temperatures and it does not get very cold in Tennessee it makes sense to switch. Any reason why I should not??
Any suggestions are appreciated.
thanks

I use 5-40 and have no issues.

Thanks Drew,
I figured that much but wanted to hear from someone that is using it.

Hi,
The issue is not whether it will work "OK"...it will....but whether MB (or whoever) will honour a claim for damaged engine if the recommended oil is not used and a problem arises due to some other cause than the oil.

Surely the real issue is why do you want to use 5/40 vs 0/40...What benefit are you going to get against what risk?

If you are out of warranty etc. then it seems like a straight forward alternative should there be a problem with availabilty etc.of the 0/40. You have kept with Mobil 1 which I recommend but of course it doesn't have to be Mobil, just an alternative which is certified to meet MB's oil specification so Shell / Exxon etc 0/40 full synthethic and carrying the MB oil specification will be OK.

MB and MB F1(race cars) market using the Mobil association / sponsor so why not stick with what's good enough for MB...or does your mechanic know better.

Stuart

The reason for the 0 is for fast oil circulation on 1st start to the overhead gear.
5 40 will prob never be an issue as some of the approved oils are that..

Bazzle

i jsut got back from the mercedes benz dealership (parts & service department). i went looking for oil and they suggested mobil 1 5w-40.
i htought it was a bit awkward because all i can find regarding mobil 1 5w-40 and mercedes on the internet is regarding mercedes trucks, but i am glad i found this forum and seems to be the actual oil i should use.

so in summary, if mercedes benz told me to use mobil 1 5w-40 - then thats the grade our slk's should use.