2010 Hyundai Elantra calls for 5W20 on the oil cap (manual says 5W30 ok for summer fill) ... Last fill was PP 5W20 and new fill is M1 0W30 . My thoughts : While start up is nice with M1 0W30 , once I get up to operating temp this oil makes the engine feel a bit restrictive and not as responsive versus the previous fill of PP 5W20 . I understand PP in a given grade is at the lower end of the given weight range while M1 tends to be at the higher end of the weight range . So in essence , the M1 0W30 is at the higher end of the 30 weight range (versus say a PP 5W30) which has to be a contributing factor in the engine performance I noted above . *If I had it to do over again the high for weight class M1 0W20 would most likely make a darn fine oil to use year round while the current M1 0W30 (even for a proposed summer fill) feels just a little too thick at operating temp for my tastes . * I half jokingly say this is one case where I would welcome this 0W30 oil to shear down a bit ! Since going to the M1 0W30 I have been beating on it pretty good (at operating temp) by winding out the engine closer to red line as I go through the gears - still the engine feels closer to a earlier time when it wasn't broken in good yet versus the 60K miles it has on it now ... Lastly , no energy savings to be expected with my current fill antics romping on the engine more - but at least I know I'm getting decent M1 protection !