Not sure if I got a lemon or anything but when I first unpacked and used it the reading was 5 inches of mercury lower than actual but you get what you pay for. Even when I pull the vacuum out it doesn't fill the cooling system properly which could be due to the vacuum issue, generally it does half of what it's supposed to do and I use it almost every day at work and still need to do it into a gallon or 2 of coolant and run it to make sure it runs through