GM says not to run 5W20 in any engine of theirs not calling for it. If you want to try a 20wt I would try Redline 5W20! It has a better HTHS then some 5W30's so it is unlikely to cause any problems. It is the only 5W20 I would ever consider running in an engine that does not call for a 5W20!
I know Toyota is adamint that one shouldnot run a 5W20 in any engine or model year not listed on their TSB as engine failure could occur. So the fact that my Mom's 2007 Camry with 2AZ-FE engine can use 5W20 and my 2003 Camry with 2AZ-FE engine cannot does not get my panties in a twist at all! You gain nothing switching from a nice synthetic 5W30 to a synthetic 5W20 or a 5w30 conventional to a 5w20 conventional!Their is no magic in the 5W20 label. In fact going to a 0W30 instead of a 5W30 would gain you more in terms of fuel economy then going from a 5W30 to a 5W20. In fact my Mom's Camry is running just fine on Mobil 1 5W30 inspite of that annoying 5W20 recomendationon the oil fill cap!
I know Toyota is adamint that one shouldnot run a 5W20 in any engine or model year not listed on their TSB as engine failure could occur. So the fact that my Mom's 2007 Camry with 2AZ-FE engine can use 5W20 and my 2003 Camry with 2AZ-FE engine cannot does not get my panties in a twist at all! You gain nothing switching from a nice synthetic 5W30 to a synthetic 5W20 or a 5w30 conventional to a 5w20 conventional!Their is no magic in the 5W20 label. In fact going to a 0W30 instead of a 5W30 would gain you more in terms of fuel economy then going from a 5W30 to a 5W20. In fact my Mom's Camry is running just fine on Mobil 1 5W30 inspite of that annoying 5W20 recomendationon the oil fill cap!