Blog Post View

Find and Correct the Source of Excessive Oil Consumption

A customer recently contacted us about a vehicle consuming 5 quarts of oil in 1000 miles. It would appear that something big has changed with the motor, and this could only be a result of a couple things. The most likely would be that the drain holes in the head have become severely restricted or sealed off with sludge. When this happens the oil pump sends oil up to the valve train (top of motor), at a faster rate than the oil can drain back down to the oil pan for recirculation. In essence the whole underside of the valve covers are flooded with oil. And the motor sucks the oil right out through the PCV valve.

A second thought is that you have a possible gasket issue, either one of the head gaskets is cracked or possibly an intake manifold gasket is blown and oil is either getting sucked out into the intake system where only gasoline and air should be present. A head gasket could also be allowing oil to enter the water/cooling system.

This could be checked when the engine is cold, by looking into the coolant reservoir for a layer of oil on top of the coolant. Engine gaskets such as a head gasket or an intake manifold gasket can only be remedied by replacement.

The most likely scenario is that the drain holes in the head are constricted or plugged completely from sludge. Auto-Rx would clean up the drain passages in the head if they are constricted. Auto-Rx would not help if the drain holes are completely blocked. Auto-Rx can only clean where oil can flow, as Auto-Rx is carried by the host oil.

Has the motor been consuming some oil at a lesser rate for some time? In the 1000 miles where the oil was consumed 5 quarts, were they done while highway driving or around town short trip driving? A quick inspection of the PCV valve might tell you whether or not sludge in the valve train is causing the consumption issues. If the PCV valve is full of wet oil, then it is likely that you have sludge issues in the head and valve train. The reason why I ask about highway vs. short trip driving is that at highway speeds if the oil is not draining out of the heads properly, oil consumption would be much greater than if this has occurred over a bunch of short trips around town.

A quick check to see if the drain holes are restricted would be to take an accurate dip stick reading, when the car has sat idle over night, with the car parked on level ground. Then run the motor for a short trip around the block for 10 minutes. Then park the car on the same level ground and take another dipstick reading. The oil level should match the original reading in 2 minutes of shutting off the motor. If it is showing less, wait another 2 minutes and check again, etc. If after 5 minutes the oil level on the dipstick still has not returned down to the pan then you likely have severe sludge in the valve train. If it never returns to the original level, it is likely that the drain holes are completely filled in with sludge and may need to be physically poked open.