I have always changed my own oil and recently wanted to measure the oil that drained from my oil pan and filter. I was surprised when I only had 2.5 qts. What is up with that. I put my new oil in and filter, and the dip stick showed at the mid mark of the safe zone or 6.5 qts. Where is the rest of the old oil?

 

Year and engine?

 

Sounds like you need to check the oil more often. Try getting a new Ford Motorcraft PCV and look for leaks..

 

Sounds like you were 4 quarts low when you changed it.

 

Take a look in that big drain pipe at the right rear of the truck bed. I think that's where your other 4 qts. of oil went. Seriously, you need to take the advice already offered and pull the dip stick more often. Might just save you the cost of an engine.

 

You should have looked at the dip stick before you drained it.