Here are a couple photo's that would tend to confirm that the VQ40 / VQ56 oil filters are the cellulose type;
To add some additional, here's a page from a motorcycle comparision of various filters, but from reading the same info holds true for light truck applications;
From talking with a Mobile1 service rep the fine media synthetic filter they have for the VQ40/VQ56 application is the Mobil Extended Performance which the phone tech guy tells me will filter about 50% of the 10 micron particles per pass, part # M1-110;
The Purolater website: http://www.pureoil.com/ doesn't give any performance or filtering info, but from other independent studies the Purolator 'Pure 1' synthetic filter part # PK14610 for the VQ40/VQ56 engines also do a 10 micron cut with an added benefit of a larger surface area of filter media available than with the Mobil 1 filters.
The Hasting /Baldwin company gave some info on their filters in that the filter that they provide for the VQ40 engine uses a straight cellulose element which gives a filter cut of 23 microns, at about 50% efficiency per pass. As an aside comment and for what it's worth, the gal who I talked to at Baldwin said that the company doesn't build filters which exceed OEM specs, so that would be why their company doesn't supply synthetic filters for the VQ40, although they supply nanofiber filters for other OEM applications, info which might also confirm that Nissan OEM VQ40 oil filters are cellulose;
Depending on which studies are looked at most state that the 10 - 30 micron size is the one which will create the most engine wear, so trying to filter out as much of the 10 micron size might be beneficial. Other studies indicate that the 5 - 10 micron size is also detrimental but require a bypass oil system to filter to that size.
As the price is only a few dollars more than Nissan OEM filters, I think I'm going to start using Purolater Pure1 synthetic filters rather than the OEM cellulose type.