Yeah I have used mine a couple times since I got it and works great. I all depends on your water. That's probably why it didn't work well for you RC. The starter filter lasted me almost 5 times.
I usually spend a good 3 to 4 hours washing my car and my girlfriend gets all upset with because she thinks I spend more time with my car than her, plus I have a black GT also. Wait till I tell her the good news!!