Answer to "air builds high pressure, purges every 15 seconds"check valve in air dryer no good you can plug signal line and hook 2 big lines together
Answer to "oil consumption the delima"You dont say what kind of motor. A 60 series (1997) owners manual will tell you that amount of oil is within normal. ALL detroits fog out the breather tube. Mine has been doing it since the day it was in framed. I was freaking out till I made a delivery to a yard full of company trucks with detroits, they were all the same as mine. you can walk down the line at a truck stop and pick out the detroits, all fogging the breather. Also - If it aint broke dont fix it - run her till she drops, just keep puting your money in the bank youll probably be suprised how far you can go.