I bought up alot of the Castrol startup 5w30 and 10w30 when advance auto quit selling it at a good price, even though the bottle says G-3 and SL, Castrol claims their GTX startup is G-4 SM, on a fax they sent. I have to wonder if this oil is the old folmula Syntec oil, re- packaged. It came out about the time Syntec changed its folmula. Since I bought the oil , I bought a new truck a 2006 hemi that get this calls for 5w20, I have been using Castrol plain GTX 5w30 in it since new, the last oil change I decided to try the Startup and it really does make a difference, it accually seems to run smoother, especially at startup. I wish they wouldnt have dicontinued that oil. Did anyone else try it? Ill probably switch to Pennzoil Platium at 10,000 or stick with Castrol GTX 5w30 or 10w30, Iam just not sold on the 5w20 for the hemi, I have the 2500 and it does not have the MDS. I live in Florida and am going to stick with a heavier oil as was used and proved in the earlier hemi s in 2003 thru 2005 models. Thanks.