Won't start, and dropping oil level

[JFP in PA]

I'd be checking voltage drop across the battery cables, both to ground and to the starter. Corroded cables often show up in the cold.

[woodsman]

You could check the fuel pressure as well. To do so you need a common fuel pressure tester that attaches to a Schrader valve fitting- should read 45lbs or so while the engine is being turned over.