[clarkz71]

To be accurate, you need to regulate the supply air to 100 psi, then a 10% reading on the leak-down tester is actually 10 %. A leak-down tester will help determine if an oil consumption/smoking problem is valve guides/seals or rings. If you hear air coming from the oil fill hole in the valve cover, and the percentage of leakage is high, you have a ring problem. Likewise, if air is heard from the throttle body, intake valve, exhaust pipes, exhaust valve. You want to see all 8 cylinders within 10% of each other. To use this tester, you need to have the piston at TDC on the compression stroke.