Driving my 4runner at 60 kmph notice a loud rattling. Pulled over and saw the oil pressure was extreemly low so i put 3qt of oil in. Now the rattling has stopped but it is making a very very loud knocking when idling and started, and when accelerating the knocking quickens and becomes even louder. I pulled the spark plugs 1 by 1 and the noise seems to be comming from the piston/cylinder on the passengerside closest to the dash. Anyone know if it's even safe to drive to a shop or should it be towed? And what could the problem be? The noise is just a very loud knock as if something is hitting something else in the engine.