tlbuser
Veteran Member
3 hours shopuld be sufficient, but as a test: leave it plugged in for 3 hours then go and check your upper radiator hose to see how warm to the touch it is. If it doesn't feel warm, wait another hour then go check again, repeat as needed. If the upper radiator hose never gets warm to the touch, I would suspect a bad block heater connection or just plain bad block heater. The block heater should warm the oil and antifreeze.