Wow, one's driving environment can be read from an oil analysis? Yes, all I do is city driving. Stop and go with plenty of heat here in L.A. Lots of high speed driving also, and sudden stops. Even took it on a trip to Vegas.

I'm not exactly sure how long in months the oil has been used, but I reckon it's under six months, even safe to say around five months. Why I use 15w 40 is because of my mechanic's recommendation--this, of course, when I was using dino oil, and my engine was consuming 5w 30 Chevron oil. That, and it's also cheaper than the 10w 30 variety. Would 10w 30 be more economical fuel wise? I'm hoping to extend my interval for at least 10,000 miles with Amsoil oil. Would 10w 30 perform better with my application?

Thanks for your time and advise.