I have a 2012 F150 XLT 5.0 V8. I bought it 2.5 years ago, second owner. Original owner was an elderly man who took exceptional care of the truck (very routine maintenance at Ford dealership where he bought it). It had @ 132,000 miles when I bought it. It now has 149,000. I have the oil changed about every 4,000 miles roughly.

I have always put 5W 20 Valvoline synthetic blend in it - except for about 2 oil changes ago, when the shop mistakenly put 5W 20 full synthetic in. I have since switched back to blend. Each time I have the oil changed, it is usually @ 1 quart low. I am currently about 4,000 miles since my last oil change and was about to have it done in the near future. 2 days ago, my low oil pressure light came on. I went to the closest parts store, let the truck sit for 15 minutes turned off, then checked the oil. There was nothing on the dipstick. I went in the store and bought 2 quarts. After filling, still no oil on dipstick. It ended up taking 5 full quarts to get the middle of the proper fill zone on the dipstick! Where in the world could all of this oil have gone?

I have had a very slow rear main seal leak for maybe a year now. But I park in the same spot of my gravel driveway every day, and yes there is some oil, but it's a slow leak, and I have not noticed it getting worse at all. Truck does not smoke or smell like burnt oil.

I took it to a quick oil change shop last time (Nov 2021), and had never been to that one. The only thing I can imagine is they didn't fill it full. Is there any possibility of something else? Could the truck actually burn 5 quarts in 4,000 miles with easy, limited driving around town and no symptoms of anything wrong?

I did notice a bunch of soot in tailpipe...but maybe that's normal with 150k miles?

Thanks for any help!
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