Hi everyone, first of I wanted to say that I just discovered this board recently and I am impressed with the wealth of information here. Well, I have a 93 NA Nissan 300zx and it is due for a oil change soon. I decided to use Castrol GTX High Mileage based on the recommendation of many on this forum. Just a few questions...is the High Mileage the same formula as regular GTX with the addition of esters and extra thickness? My owner manual states to only use a ENERGY CONSERVING labeled motor oil and the I did not find any such label on the Castrol container. Can anyone explain this? Thanks a lot!