Pinking / Tappety sound

[RustyMX5]

I've got a 2003 Forester (SG with the EJ20 block) which seems to make a pinking / tappety sound between 2,000 and 3,500 rpm. The engine has done just a smidgen under 170,000 miles and the previous owner (my father) didn't always keep an eye on the oil levels so it has been run with barely a drip on the end of the dipstick at times. Since I've taken it on, I've been keeping an eye on the levels and it doesn't seem to be drinking too much oil and the last service indicated that there wasn't anything out of the ordinary that I needed to be worried about. I'm currently chucking in 0/30 oil as that seems to be the recommended weight for the engine.

Any ideas what might be causing the pinking sounds and what I could do about it?

[RustyMX5]

Thanks chaps. I'll finish off my current tub of oil and then move onto something slightly heavier.