BMW Synthetic Oil

[Aaron C Liu <aaronliu@xxxxxxxxxxxxxxxxxxx>]

I recently switch to Synthetic Oil, and the service was done by a BMW
service Dep. in Seattle.  They used Original BMW High Performance
Synthetic Oil and it is rate as 5W-40.  I did a little research over the
net, but having problem finding the information on this type of oil.  All
I can find is 5W-30, or others, I can't find anything that's relate to
5W-40.
I think this is the one they used on the new E-46 3 series.
I like to know how often should I change the oil (I used to change oil
every 3000 miles with regular oil) after switch to Synthetic oil (I used
this car as daily drive. both city and highway, sometimes stop and go)
Can somebody tell me what's the difference between the 5W-30 and 5W-40?  I
searched Chevron and other oil company web site and learned that 5W-30
Synth. oil provides better fuel econ. and low temp. performance.  How
about 5W-40? is it better than the 5W-30?
Thanks

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Aaron C. Liu		North Seattle Community College
E-Mail: aaronliu@domain.elided
Home Page: http://nsccux.sccd.ctc.edu/~aaronliu
	   http://fly.to/aaronliu
ICQ: 25763155

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