My mom has a 2004 Rav4 with a 2AZ-FE that calls for 5w30. Has this been back speced to use 20 weight oil? My sister has a 2010 Scion Xb with the same engine that calls for 5w20 and/or 0w20. Have these engines changed any between the two vehicles over the years? Are these engines known sludgers? Thanks and looking forward to any insight on this engine.