I have 3 vehicles that I'm considering useing CI-4/SL 4 15w40 fleet oils in. I have not owned any of these 3 vehicles very long, so I have little history as to how they react with any viscosity. 1991 Mercedes 300E 167K Miles 1984 Pace Arrow motorhome 454 Chev 75K Miles 1997 Ford F150 4.6L 86K Miles I feel fairly comfortable using 15w40 in the Mercedes and motorhome, but may be better off using 10w30 until the F150 exceeds 100K miles. It would be nice to be able to use one oil on all vehicles, I will probably go with Pennzoil 15w40 LL or Chevron 400 Delo. The weather here rarely goes below +32F in the winter (mabe a few days of +26F), would 15w40 be acceptable to run all season here? My Mercedes manual recomends 15w40 for temps above +5F, but I have read Delo has a -38F PP and Pennz -33F PP, I'm not sure what that means in terms of cold weather capability. One final thought, I would at some point like to try Schaeffer, who would be my best source? Thanks for any input.