I am running a grade '7' plug (NGK ILFR7H) and am wondering if it will be prone to fouling if I do short trips that don't let the engine fully heat up before switching off. The car is a STI MY07 2.5 and runs a MDX555 turbo and Perrin FMIC.

Does anyone else run grade '7' plugs and also does short trips ? Any issues ? or am I being paranoid

 

If the off boost mixture is correct as it should be with the closed loop system working, then there should not be a problem. I've run 7's for years and it's never missed a beat.
As the trips are short enough not to fully warm the engine, I'm assuming you stay out of any meaningful boost! I also assume it's properly re-mapped for those mods.

JohnD

 

Yes, I only drive off-boost, under 3000rpm and light throttle when the temp is under 85c. It was indeed mapped for the mods on the car.