Is this OK to do, as I've heard people doing it and it shows with smoother running engine as the sludge/dirt at the bottom of the fuel tank sometimes flows through and gets caught up.. is it ok to do and what kind of solution to use?

 

Well as the fuel is taken from the bottom of the tank this must mean all our injectors are clogged up with sludge.

Fortunately modern quality petrol shouldn't have much by way of dirt in it and you will find there is a fuel filter in the line between the fuel pump and injectors to remove any. The fuel filter should be replaced at the intervals specified in the Subaru service schedule.

You can get your injectors cleaned, and there are various fuel additives available that claim to do so but whether there is any value in doing this is I'm not so sure.

 

I tried the STP injector cleaner last year. Not very impressed with it - car seemed very hesitant and went through about 3 tankfuls of petrol before normal service was resumed - whether it was better or not, I couldn't tell.

If I thought I needed it done, I'd pay somewhere to take them out and do it properly.