kinda depends on how fast the t,t,t, goes away. if its only for 5-10 seconds i think your ok. any longer than that and i would try a quart of gunk motor flush (dyrections on the can), drain that oil and motor flush mixture out, put on a new filter, and fill it with Rotella T synthetic 5-40W oil(get it at walmart for about 10-12 bucks/gallon). my thoughts on a probable high milage cold weather leaking down lifter. mike