Quick Oil Weight Question
 

I have a 1989 F250 with the 460 (7.5L). The previous owner always used Castrol 20-50, and I have followed that recommendation for the year I have owned this truck. I just discovered that the owners manual recommends 10w30 for 0 deg F or above or 15w-40 for 10 deg F or above. Is the 20-50 too thick? Any thoughts? The engine occasionally squeaks a little when warming up from a cold start, indicating that it might not be getting lubricated properly due to the oil being too thick.

I live in a very mild climate by the beach in Central California. Winter temperatures average low 40 high 60. Summer low 50 high 75. But the truck is occasionally used for long road trips all over the west towing a small trailer. Still, it will rarely see anything below 20 degrees or above 100.

For what it's worth, I also have a '73 Ford Wagon with an older version of the same engine (460). For that, I have always used 10w-30 in the winter and 10W-40 in the summer, per the manuals recommendation and have never had problems.

i normally like to stick with the oil that the truck has been using but i belive that oil may be too thick.. try swapping it for a thinner oil and see if the noise stops.. then drive it for a good 50 miles let it cool down completely and start it again to see if it still makes a noise on the start up.. it could be that you just have a bad oil pump.. my father had a truck that had similar problems we thought the oil was wrong but it was a bad oil pump and just wasn't getting oil to the top end.. had a nice knock in it for about 30 seconds.. finally replaced it and it went away.. so don't scratch that off your list of problems just yet..

The previous owner put over 100,000 miles on the truck always using 20w-50. Hopefully that didn't do any damage to the truck.

I think I'll go with the 15w-40 (per Ford recommendations) and see if that makes a difference on startup. The squeaking is really minimal, definitely no knocking or anything like that, but being somewhat of a religious mechanic, I don't tolerate anything but a perfectly running engine.

I run 20/50 year round in all my older fords, Never had any problems and it gets pretty cold in Utah in the winter. My 76 E150 went over 250,000 miles running the thicker oil. and still ran great when I sold it.

Thickness ???
 

Geoff. your truck is an 89 and it was designed to run on "thicker" oil and we can agree on that... right!!! I live in Nevada 40mi from Death Valley, I run 15-40 year round. When I change oil first thing I do (after draining) I put in a QT of Lucas oil treatment then top it off with the oil. I only use Shell Rotella 15-40 with 214,000 + miles ... NO ISSUES :-jammin !!! I also use a NAPA/WIX filter # 1773. What you described could be your oil filter allowing the oil to drain back in the pan, thus giving you a "dry" start situation!!! All filters should have a back flow prevention device inside... better the filter, better the device !!! You can Google oil filter comparisons and make your own choice ... Quality vs. Cost.
The most recently mfg. trucks are designed to live with thinner oil (tighter clearances)... 5/30, 5/20, 0/20 but out old iron was not.
There is a website known to FTE folks... I think it's Bob The oil guy, or something like that others can correct me if I'm wrong. Check it out but remenmber how old your truck is !!! Dave:-wink :-X22

Did you see if it was a belt ???

ive always run 20/50 castrol syn. in my 90 with 175000 miles on it. im in arizona. i started going with castrol high mileage oil.

Check this link: Motor Oil 101 - Bob is the Oil Guy and read the whole article, 101 through 201. It's long but well worth it. It will bring you to a whole new understanding of engine oil and how it really works. You will find the answer your looking for and learn that most people are spending way more money on oil than they need to. Like oil changes at the age old standard of 3k miles or 3 months, it's a wast of money! I know crazy, read the article!
Something I learned from it that may apply to your question... Use the lowest first number always, 0w or 5w because it only applies to the start up oil thickness. Whether you are in a cold or hot environment you want the thinest oil at start up you can get to put the least amount of load on the oil system. And stick with the second number that your owners manual recomends, 20, 30, 40 ect. That second number, as I'm sure you know, is the weight or thickness of the oil at normal operating temp.
... Read the article it will speak for it's self!

I would run whatever weight the OM calls for if it was a new or rebuilt engine.
BUT
In a high mileage engine I would run what ever weight required to get the correct oil pressure at operating temperature.
If you get the correct pressure at 190 degrees F on 10W40 it would be good. Use a good mechanical gauge for testing the ford dash gauges are for show only!
The ford bb engine requires good oil pressure to keep the mains lubed properly. Before I went through the last rebuild on our 460 I was using straight 30 diesel tractor oil to keep it running without knocking.
Believe it or not, straight 30 holds more pressure at 190F than 15W40 on a given engine.
The 2 stroke detroit diesels require straight 40 weight so it is available if the bearings are really a mess.

I run 15w40 diesel oil in our 460 and Mopar 440 both engines are doing fine.
I am in DALLAS and the temp rarely drops below 30F, its the summer that a bear at 105 for weeks on end. 5W30 at that temp is VERY thin at temp.
I also ran it when I lived in Napa Ca.

Thanks for all the input. To respond to some of your questions/comments: I have read "Bob the Oil Guy" column in the past, so I am somewhat educated on oil grades, viscosities, etc. I previously was running a motorcraft filter, which I believe is pretty good quality, so I don't think that was causing a drain back condition.

I ended up putting in castrol 10w-40 with a wix filter. Drove it around town for the day and everything seems fine. I know that the stock gauges are not that great, but I'm getting identical oil pressure readings as I was with the 20-50, so I would assume the pressure is about the same.

I will report back after I've put some miles on the truck.

My 2 cents worth is the thinner viscosity is for colder temperatures. I live in Texas and for may years religiously used straight 30 weight oil. Now as time has passed I have moved into full synthetics and use multigrades on everything. In the winter I try to run 5-30 and in the summer I run 10-30. Either is perfect for where I live and the normal temperatures outside. Your primary concern should be when you first start the truck A) does it knock? B) Is it just a tap or a knock? C) Is it over instantly or lingers as in waiting on the thick oil to reach the heads?

Where you live I would reccomend a good quality 10-30 motor oil. I've actually back many years ago when I traveled for work spent alot of time in Bakersfield and San Bernadino and the climates IMHO would be suited for a good 10-30.

The truck definitely does not knock ever, even on cold startup. I don't think that the squeaking that I'm hearing is oil related, probably just a loose belt as someone mentioned. The previous owner maintained it religiously to the point of overkill. Oil changes every 2,500 miles on the dot. Gear oil and differential oil changes every few years, etc. The truck runs pretty much like new at 151,000 miles, besides the squeaking issue I have mentioned.

Anyways, I decided to go with the 10w-40 over the 10w-30 because the truck will see at least a couple long distance hauls towing a trailer over the summer time. I may switch over to 10w30 for the winter. Living in California, The truck will never see temperatures cold enough to warrant 5w30.

Like I mentioned in the first post, I have a '73 Ford Country Squire Wagon with the same 460 engine. Carbureted as opposed to Fuel injected, a straight up timing set as opposed to 8deg retarded, and with significantly less emissions controls. But overall, the engine internals are pretty much the same. I have always run 10W-30 in that and sometimes 10w-40 in the summertime. I have never had any problems with that car (now at 121,000 miles), so I think I'll follow that for the truck.