My diesel loving brothers...I did not mean to start anything, just expressing what i have learned thus far in the oil busuiness.. oh, i looked for mobil 1 15-40 and thier turbo diesel 5-40 at wally world.. they dont sell it. and if anyone can buy amsoil cheaper than walmart pricing more power to you. there are several dealers in my area and none want to give a price cheaper than what is on thier website. but some believe that if they pay alot they recieive alot. I don't want to pay 140 snaps to change my oil on top of filter prices when i know of another product just as good (or better matter of opinion) for 1/3 the cost. to each his own. The reason for me sticking up for exxon mobil and conoco phillips is the fact that after talking with reps, people from the factory behind the scenes dudes you get a more insight on what goes on vs. just advertising on a fancy bottle. Any way i'm not going to be able to get the formulas and share with everyone, but if the local guys wanted to come into our store id be glad to show you around! As some has stated-- nailed it--just a preference. I dont want this to get like an old thread that comes to mind... how one auto make is better than another. If it rolls coal, its good enough to me!

 

They now have a new Mobil One it's called Mobil One ESP:

I will be using this one in my new 2010 Jetta as it's the only 5W-30 I know of that meets the newer Volkswagen 507.00 specs:
MOBIL 1 ESP 5W-30 SPECIFICATIONS MEET:
ACEA A3/B3/B4, A5/B5 ,C2/C3
API SM, SL, CF
JASO DL-1-08
APPROVALS:
BMW LL-04
MB-Approval 229.31/229.51
Volkswagen (Gasoline/Diesel) 504.00 / 507.00
Volkswagen (Gasoline) 502 00 / 503 00 / 503 01
Volkswagen (Diesel) 505 01/ 505 00 / 506 00 / 506 01
Porsche C30
Peugeot Citroen Automobiles E06-N3 / D06-N3

They have one that might meet your needs: Mobil 1 ESP Formula M 5W-40:

Euro Synthetic Oils - Mobil 1 ESP 5W-30 & ESP Formula M 5W-40 Oils

 

Not a diesel so I do not know how it'd handle soot, but Castrol Syntec is the only engine oil I found to calm down noisy lifters. Used a 5-40w in the winter and 10-50w in the summer.

Within 10 miles the lifters would make serious noise using 0-40w Mobil1