My mechanic swears by GSF.
I aren't so sure, because if *I* buy the parts locally, Euro Car Parts tends to be cheaper for even their better branded stuff. And I end up paying less than my own mechanic does from GSF.
Another thing which puts me right off GSF is when I'm sitting in the comfort of my own home planning on bits I need, their website is tripe. Euro Car Parts is far better.
Saying that all my cambelt stuff, thermostat and numerous filters are from GSF and are fine but mostly MANN stuff
