Freedom is not free
Join Date: Sep 2007
Location: Sioux Falls, South Dakota
Don't do it. You do not want to mix different viscosity oils. In addition, the additive package between the 15W-40 and 5W-40 is different. Since the additives work in conjunction with each other you might be messing up the performance of the oil.
Wher in Oklahoma are you? Just getting ready to move from Fort Sill/Lawton.
2003 F250, Wildman tunes, Faubion trns, Swamps 175/146 SS,van turbo/WW, DI Intercooler, oilguard bypass, intank & pre-pump, reg return, Firestone air bags, Bilsteins, 350 HP/692 TQ
2000 Excursion- Pwrd by: T Wildman 6 pos chip, CT Performance Suspension, Riffraff Diesel Performance, J&M Tranny, 4" MBRP, 6637 filter, intank/prepump mods