Lot's of oil info. to be drilled around these parts...
Most of these guys have bought into Mobil 1, maybe I should have an alias CastrolDood.
I have driven air cooled(high heat), high compression, turbocharged, high revving engines most of my life. I've cared for them diligently using GTX with no engine problems whatsoever. I only varied the viscosity with the season.
What do you call the improvement to this finely formulated "dino" oil? Syntec!
You'll learn lots about oil here, I've learned about soot dispersing "C" oil. Since I always change regularly, hopefully my previous ignorance has not hurt my engine life.
I can tell you GTX will help extends yours!
I recommend Syntec simply now because it's synthetic advantages are becoming cost effective. It's like this, if I get an extra .5 mile per gallon. After a couple of tank fulls I gotten an extra gallon of gas. That's $2.25 in these parts. If take the 3000mile per oil change and divide the 230 mile per tank, I get roughly 12 fill ups or 12 extra gallons. That's roughly $27 I've saved using synthetic. Add to that the cost of the "dino" oil and you've got my cost on Syntec for the ML.
This "brain-working" is all assumed approximations, however, it is conservative and you can see that was once the least important characteristic of synthetic is now relevant. So enjoy all the other benefits of Syntec as well