I don't want to start a war here, but just want to share some info., and hopefully generate some useful discussion from those in the know. I worked in a fleet operation for 31 years. The oil on tap was always 15/40. We never had oil related engine failures until '92 when the 4.6 showed up in the crown vics. Ford said " you will use the prescribed weasel **** oil or the warranty will be nixed. " ( ok, they didn't exactly say it that way, but the message was clear ). Funny thing happened---slowly but surely, the cop cars started seizing engines. Sometimes we would have them in the shop for a few days, and when we went to start them, they'd click and the battery cable would get hot, and there went another one. Long story short, approximately 40 engines between '92 and '97 or so, toes up. The problem? The oil was burning to a crisp, and that black carbony crap was plugging the oil pickup screens. Conclusion? Oil starvation. Upon teardown, they were a filthy mess. Solution? The City of Spokane said stick this crap in your butt, and went back to 15/40, and the engines are now going to auction with 120000 miles on them, and on the occasion that a cover is pulled, the underside looks like new, and NO OIL RELATED ENGINE FAILURES. You know what?--Ford wrote the city of spokane a check for 60 large when all was said and done, which tells me they admitted at least some responsibility. Now I'm driving around in a pickup that I've got a lot of money tied up in, and wondering amid all this debate about oil, just which way to turn with my 5.4. Motorworks is the premier engine rebuilder in Spokane, and they are seeing a high number of ford modular engines with premature failure. Their conclusion? Weasel pissitis. Their suggestion? 15/40 high grade like Delo. So, whaddyathink?

 

change the oil regularly, use a good filter, don't worry about it

 

I have read many places that the correct oil viscosity, per Ford. is needed for the lash adjusters to work correctly. So, that would mean that a heavier wt oil would inhibit top end function and lubrication.
Your results are interesting.

 

I am not thoroughly educated on Ford's most recent decade of motors or changes to those motors. I find it interesting that Ford changed to a 5w20 wt. oil to meet CAFE requirements AND have read and heard that they made NO changes to the triton motors in conjunction with that weight change. Don't know if it is true or not.

I have always been a "thicker oil" guy. I owned 3 Pontiac Grand Ams, all required 5w30 per oil cap. For 14 years, each one received 20w50 Castrol every 2500 miles. Never ever had a problem and never had a fuel mileage issue. In fact, my 1986 model got better fuel mileage than my friend's 1985 did with same 4 cylinder motor. He ran Havoline 5w30 in winter and 10w30 in summer.

I have had my 2005 S.crew 4x4 Lariat for 2 years now. Bought it with 10 miles on it. To date, of all the various 20 wt. and 30 wt. oils it's been given, I get the best mileage with Amsoil 0w30.

My friend/neighbor, his brother, and their father all have F150s and 2 Excersions. All have over 100K miles. All have been using/burning oil. All have been using Mobil 1 5w30. Recently they ALL switched to Royal Purple
10w40. So far, (about 1500 miles on each vehicle with new oil), none have used up any oil.

 

I'm not real confident with this story of mass engine failures due to oil viscosity. I have worked in the Romeo Engine Plant dyno since 1989 when the only department in the plant was Dyno. The rest of the plant was being referbished into the current engine plant. We and Dearborn dyno were at that time Dyno testing prototype 4.6 engines prior to production. I am still there today. We receive most 4.6 dealer pulls and VO returns from North America to our Dyno lab. I have seen a few ( less than 20) police engines that were sludged up really bad. Our determination on this was the inferior bulk oil that was being used by some police and fleet customers. Inferior oil combined with severe duty cycles is a poor combination. This was not caused by viscosity issues. I have not found a 4.6 of any family (truck or car) in the last few years that has had a sludge problem and as you know we are now using 5w-20w oil verses the 5w30w during the years you state. I might add that we beat the hell out of the 4.6 using 5w-20w oil and dyno failures are virtually nonexistant. I am not here to disput you but I have been on the forefront of dyno testing this engine since it's inception and I disagree with the diagnoisis that was give to those seized engines. By the way the 4.6 is one hell of a bullet proof engine when regular maintenance is applied. Personally I think viscosity is way over blown. When we were running slave engines just to test pistons we would change the pistons out dozens of times on the same block and run them to death. These beat up 4.6's would start running low oil pressure so we would pour straight 50 weight in them and just keep beating them. God only knows how many hard miles they had on them. Amazingly I don't recall ever blowing one up. Thanks.

 

I have a 97 F150 with 220,000 miles on it. Ran "weasel ****" in it its whole life.

 

I agree... it's not so much viscosity, as it is quality. There's a reason you can get a 5qt jug of wal-mart oil for the same price as 2qts of Amsoil.


Cop cars spend long times idling and slow around town driving, what typically falls into the "severe duty" category. That plus "weasel ****" oil will have bad results, no surprises there.

Use name-brand oils. Castrol, Mobil1, Amsoil, RP, ect.

People always ask about how long they should wait between changes, expecting some carved-in-stone definite answer. Your engine has a dipstick for a reason. Check the oil's level and color. If you're really finicky you can send a sample to get analyzed to really determine how much "life" it still has.

 

I agree totally, use a high quality oil, & filter, & change it regularly.......

 

yep... lash adjusters will not work correctly with anything but 5/20... i have been using it for 124k miles and running the heck out of it and it doesnt smoke or burn a drop of oil.

 

Castrol here 5w30 - for 200,000 + miles and change it every 3000 religiously. I don't burn a drop between changes although I think I have a head gasket leaking - that's a first . I never had oil on the side of the motor and it looks to be coming from the gasket . I can't complain , they never been changed.

 

Good feedback. I'd like to hear from someone who has run a quality heavy viscosity oil for a couple hundred thou. and see how they're holding up. I know that short drive cycles and poor attention to oil changes are a factor. I've had a lot of fords, and driven the crap out of them all. Always ran quality 10/40 or 10/30, wix premium filters, and dumped at 3000. Also l drive longer drive cycles, so I'm good and warmed up every drive. When I change oil, it always looks like it's still golden brown. This is the first rig I've put the 5/20 in, and only owned it for 2 oil changes, so I don't have a basis to judge by.

 

I was always a believer in running 10W40 or 20W50 in my cars and trucks because I live in Phoenix. Changed oil every 2000 miles religiously and always ran Dino oil.

I keep cars for a long time and usually end up rebuilding the engine myself. between 150,000 to 200,000 miles.
What I have found with the high viscosity oils is lots of build up of carbon in the ring grooves- and very lettle wear on the bearings. At about 130,000 the oil started turning darker sooner indicating loss or ring seal.



My latest stable I have been running semi syn on two cars and M1 5W30 on my 97 F150 4.6. f150 has 167,000 and doesn't leak a drop and use 1/2 qt. in 4000 miles. Oil stays clean between changes and the engine runs as good as it did on day one- so hard telling when it will be worn out.

My ancient well abused 83 tbird 302 had deposits in the valve covers and on the push rods with 20W50 dino. After rebuild I run 10W40 semi syn. AT 70,000 miles on rebuild no deposits in the valve covers and the oil stays much cleaner between changes than with dino.


Bottom line- lower viscosity synthetics and semi synthetics don't form deposits like dino oils, give better ring seal, can run longer between oil changes. Don't know about the bottom ends, since engines are lasting longer and haven't torn one down since making the change to syns and semi syns 10 years ago. FWIW

 

any viscosity will do. I sell a lot of 15/40 to people who run it in diesels, boats, cars and trucks. They got in the habit of buying it because it used to be the least expensive of what I sold and is widely applicable. They still buy it because of experiences like the original poster describes.

Clean oil is more important than viscosity any day. I run 5/30 in my 2003 5.4 which is supposed to use 5/20 - there will never be an issue with that application and you would have to a few decimal places to argue mileage.

The syn vs dino debate is endless but low flow or high heat application (accidental engineering deficiencies) or going too long between oil changes is one are where syn accels because it wont boil off. No weak link in the strands to burn away and leave remaining oil thicker.