I have an '03 Protege 5 - have tried the following:
Mobil Clean 5000 10/30 - quiet running
Pennzoil Platinum 5/30 - quiet running
Pennzoil Yellow Bottle 10/30 - quiet running
Valvoline Synpower 5/30 - tons of valvetrain noise
Personally, I'd pick a Pennzoil product in 5 or 10/30 and keep it there.
I don't think it's any lack of respect from the forum - GTX has been around for so many years, I think it just gets lost in the shuffle when new products hit the shelves.
The UOA's posted for GTX are typically very good.
I use and like both. I put Ultra 5-30 in my Mazda Protege5 about 300 miles ago. Once the car is warm, it 'seems' a lot quieter and smoother than the last fill (Platinum 5-30).
My first tank of gas on the Ultra fill did net about a 4MPG increase without a change in driving mix or habits - not...