Bob I also use the synthetic oil in my Rav. I have been to a few racing events and the word there is that one should not use synthetic in a new motor because the tolerances are very tight in a new motor and synthetic will not allow higher temperatures to be achieved for proper break-in. Keep in mind that these are racing motors...production motors like the ones in the Rav do not have such tight tolerances and will most likely be ok to use synthetic. The word from most companys that produce synthetic is that it is ok to switch over to synthetc oil AFTER your first oil change. This may be just a "cover you butt" clause they put in there for legal reasons.