After the switch to 0w20ep the engine is quicker but also slightly noisier after warmup. Startups have a little more juice with 0w20 but both weights are nearly identical (smooth with no wierd noises).I have owned the 1999 expedition since new and it has had only mobil 1 after the factory fill drain. It used to get m1 5w30 upto 100k miles. Since then it has had mostly 0w40. On one long trip from chicago to miami in 90 plus heat i have used 0w30 afe with good results too. The expy sees a lot of long trips 12 hrs a day at 70 plus mph. It has burned a quart of oilevery 700 miles or so from day 1 (1999). After reading a lot regarding how ford modulars love mc 5w20 and great base stock of m1 0w20 ep i decided to switch for the winter to see how it performs. Now thinking that i made a mistake in switching i went through all reviews on mobil web site and found quite a few ford modulars that have made it past 250k miles on 5w30 despite ford tsb to switch to 5w20. I have never had any problems either with the heavier weight oil. Once on a gruelling drive from ca to illinois i have used m1 15w50 as top off oil during the drive with no ill effects. By the way i filled with 6 quarts as told by owners manual. I have done this since 1999. Never bothered to check it after that. Well this time i drove for 30 miles and decided to see if there was any burnoff with lighter 0w20. The dipstick was halfway between add and full mark. I was like wow half a quart burned off in 30 miles with 0w20 After internet search i saw that to get the level to full it takes 6.5 quarts. Learn something new everyday (embarrasing too). Does anyone know what is the optimum oil pressure for the chain guide tensioners (too much and they wear out and too little is not good also:) Also molecule size in 0w20 is smaller than 15w50. What happens when you mix them. Do they become one size or they retain their sizes which could result in small ones going in tight spaces and big ones going where space allows. Kinda a like best of both worlds. I am thinking of draining 1 quart of 0w20 and replacing it with 15w50 to see the effects on engine noise and power. Hoping to somehow end up with an optimum mix lol. 2.5w25.