I am using index paper, no cards, to do the same with mobil 1 0w40 on my 95 BMW 525i with 107,000 miles.
After almost 3,000 mile the blotter looks almost the same as your 800 mile blotter, perhaps a bit darker. I find that the oil continues to spread over time and looks lighter. Even so, the oil on the dipstick looks dark brown.
I am glad your blotter looks similar to mine. I may also try mobil 1 5w40 truck and suv next.