2012 yukon xl 5.3L, drove on a 600 mile road trip. all the way out was fine, I check guages frequently. On the way back home about 250 miles to go i noticed oil pressure dropping to about 10. I pulled over and checked the oil and only had to add 1/2 Qt. used the rest room and came back out and looked all over for leaks and didn't see anything. Started the truck up and pressure was good for about 100 miles and had to pull over and stop the car again. waited a few min and on restart pressure came back up. Did this like 3 times before getting home. Any ideas on something simple before I take it to a shop. I saw a youtube video of someone adding a engine clean product to the oil and running it for 5 min then doing oil change. I got a check engine lite when it started dropping the 2nd time but no serious warnings if there are any for this? I am going now to see what the code is.