120 k miles ,5 k oil changes all with Mobil 1, 2500 mile on oil
250 mile highway drive 70 -75 mph checked after 20 minute no reading on tip, 40 minutes on the tip, 1 hour 1 of 4 lines, 2 hours 2 of 4 lines, overnight 3 of 4 lines. 30 min city drive 1 of 4 lines, hour 2 of 4, 4 hours 3 of 4 lines. Never have seen anything like this before. Any ideas?

 

sounds like the engine might be sludged up
I would take a look under the valve cover.

 

I am guessing this was gas getting in your oil?