I guess they kept the same high temp testing for GF-5. Some older posts on various boards (late 08 early 09), mentioned that the high temp testing was going to be different.
I might try some TC-W3 in the tank and see how it goes. Titan out of warranty anyways. I might use some old 2-stroke gas/oil mix that I have sitting around from last year. I will put in a gallon of that stuff first (my tank is almost 30 gal).