Fuel could be a possibility, I think that the almost empty tank is more likely, particularly since we've just had that hot stinking humid weather for the past couple of weeks.
I've used Woolworths Premium a couple of times with no noticable problems. Perhaps for your next tank you might want to try Shell Optimax. Don't know what they do to this fuel but the few times I've used it in the SVX and the Liberty it seemed to make the cars run smoother. (Might only be wishing on that score as I had to pay "Real Premium" prices for it)
Kenn
