This may be a stupid question but I am preparing to tackle a head gasket job. Why does one have to drain the oil? Doesn't the vast majority of the oil end up in the pan. I can't see why draining the sump will reduce the amount of oil in the head. I understand why draining the block coolant is necessary as their will be a significant amount in the head before draining.

The reason I ask is that I recently changed the oil and would prefer not having to refill three times in three thousand miles. I am planning to change the oil a couple hundred miles after I finish the job to get rid of any new metal or assembly lube.

It has to do with contamination.

You don't have to drain the oil before pulling the head, but if you don't you really should do so after re-installing the head and before firing the engine. Some coolant and gasket debris is almost certain to get into the oil when you remove the head.

Thanks for the input. I guess I'll just bit the bullet and drain the oil.

Thanks for the input. I guess I'll just bit the bullet and drain the oil.

Cheap insurance.

Dan

drain it after you put it back together.