Mileage just dropped to 22 mpg

[strobe]

I am on a short trip this weekend and all of a sudden I am running as low as 22 mpg ???. I typically run mid 30's. Nothing has changed since my last trip, other than the oil, and I am at a loss as to the cause for this drop. The only thing I can think of that the clutch is slipping. I have noticed little bit of a lurch when I put it in first gear recently that I never used to have, but other than that nothing odd. Any ideas, or is the clutch the likely cause?