my jeep has 169,000 miles and runs strong.always changed the oil every 2 to 3,000 miles.last week i changed the oil and used lucas oil stabilzer minus a quart of oil.the oil pressure in my car goes from 0 to 80.it would always go a little below 40 at idle then go to about 42 or so at normal driving speed,now the pressure is always above 40 sometimes near 70.its always high now.what do you think happened here.what can i do to make the oil pressure back to normal,i already changed the oil again and that helped but not much.thanks for any advice