I just recently changed my oil at 15000 miles. I'm using Amsoil 15-40W synthetic oil. The manual says 10 qts. I also have the Amsoil BMK-17 dual filter. I fill both filter with oil before installation, then put 10 qts of oil in the oil pan. Check the oil after truck was level OK. Ran the truck for a day check the oil was reading about half on the dip stick. Ran the truck for about 75 miles and had my truck on level ground, checked the oil dip stick and was barely on the dip stick, checked it a couple of more times. left the truck on level ground and put a tarp under it to check for leaks. and also ran my hand around for leaks, NONE. Next day ran the truck for about 20 min.,shut off the engine looked for leaks NONE,check the oil dip stick still just touching the dip stick, added one qt. of oil. checked the dip stick prefectly full. Been running truck for two weeks, every OK

Are you checking the oil immediately after shutting down? If so, the level on the dipstick will be lower since all the oil hasn't drained back to the pan. I check mine cold or after the engine has been shut down for a ˝ hour or more. Also check several times… The dipstick can fool you… Some folks have drilled holes in the end of the dipstick to get a better indication.
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Yes; I wait about 1/2 hour to check even the next day. I changed my oil about 7500 mles and had the same setup and everything was OK. This time the only thing I can think is maybe the lines going to the Pre-Luber and out of. Maybe they were completely empty. But I don't think they would hold a qt. The only other thing that changed was this oil change was in Delaware and the other oil change was in Florida at 7500 miles. Crazy isn't it.
Thanks
GMC-DMAX

Could it be the bypass filter wasn't full when you prefilled it? I know on mine, the bypass filter is very hard to get prefilled due to it's more retrictive filter media. just my .02 L8R

I have the same setup and I need 12 qts to fill mine up. I agree its' hard to fill up the bypass filter and the lines do completely empty on my truck so you have to refill them. Just my .02-

Blue Max
That is what I put in my truck was 12 qts plus filling both Amsoil oil filters, maybe the bypass filter wasn't fill up and I thought it was. Thanks for all the great answers. Next oil change I will keep a better eye on it.

I have the same setup w/o preluber and it takes 12 to change both filters and oil. It is 11 or a little more if you only change the full flow. If you just added the preluber, then that is most likely it.

Amsoil dual remote bypass here too. 12 quarts with the BE100 bypass and the SDF26 brings my level to the top of Full on dipstick. It may take hours for all of the oil to drain back to the sump.