07 avy

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I have an 07 Avalanche 5.3 and two weeks ago I pulled my car trailer about 2 hours to pick up some house materials (about 1500 pounds). Well I checked the oil the day before and it was fine, the next morning after getting back my low oil light was on. When I checked the oil it was barely on the dipstick. It has not done this since, I made the same trip this past weekend with about 3000 pounds and it didn't lose a drop I can not figure this out after it happened I was worried and did a compression test and all was fine all plugs looked like they were burning good etc. Any ideas whatwould cause this? I read that when these engines switch to 4 cyl the valves are oil activated I wondered if this could have something to do with it, maybe one stuck or something.