I imagine that PU will not meet the GM Dexos spec since it isn't an energy conserving oil, doesn't have ACEA A1 or A5 specifications. Also, Pennzoil's website states that PU meets GF-5 cleansing and protection standards, no mention of fuel economy. In the PP section of the website they don't hedge, it meets GF-5. It is interesting that PU is more expensive than PP (for the time being).