I would stick to 5w-20. I run the motorcraft blend since Wally world sells it at a good price. Combined with a motorcraft filter that I know has the correct drainback valve, and regular intervals, there is nothing else to worry about. Just check at fill ups when towing heavy as they do get thirsty when you work them. I wish our van driving Amsoil friend the best of luck finding a friendlier forum than this where they will accept his easily offended short fuse rants. Life is too short to be offended by everything.

 

If you are truly interested in oil questions, go straight to:

www.bobistheoilguy.com

and that web site will forevermore get you the straight scoop.

Pap

 

With regards to "Dino" oil, it hasn't existed for decades......and with regards to what is a "synthetic", that has been decided by the courts...

With regards to syn vs non-syn oils, today, all oils are are considered synthetic. While I am not promoting this company nor their products, they have an excellent, detailed description as to how & why all oils today are considered “Synthetic” Synthetic Motor Oil and was confirmed through legal proceedings http://www.scribd.com/doc/217558103/...s-Day-in-Court.

Mfgs such as castrol, are actually using a oil base that is not by previous industry standards to be even considered a "synthetic", was sued (By Exxon/Mobile IIRR) and they won in court because they were able to demonstrate with additives they were essentially delivering a syn product. When looking at all the refineries in the US (2014), the only one really capable of supporting 100% synthetic oil manufacturing is Chevron/Phillips refinery in Texas…and it is not promoted as a synthetic oil.

 

I switched to 5w-30 as soon as my 3 year warranty expired. A couple MYs prior the specs were 5w30 and nothing changed with the engine. I have been running 0w30 in the winter for the last two years and it does help cold startups.(which has come in handy with the cold temps we had here) Filters used are FL820S or the Purolator Pure One equiv.

 

The company I work for runs hdeo fleet wide explorers through 988 cat loaders get the same 15w40 all the 4.0 5.4. 6.8 make it to 175000 just fine now we have 6.2L on hdeo so far so good

 

I run my v10 on 5w30. I switched because of oil consumption. After i have made the change i can now make it to oil changes with out having to added oil. I don't think ford redesigned the v10 after the changed to 5w20.

 

around 2000, the ford pitch was use 5W30. then around 2002, the ford pitch was use 5W20. then when folks started to complain about ticking noises, the ford pitch was to use 10W40.

my opinion, based on understanding what the numbers before and after the "W" really mean, use 5W40 oil blended for "diesel" engines during extreme heat months.

 

I just did my first oil change on my new to me 99 F250. I don't know what the previous owner had put in, but I used Castrol Edge 0w-20 full synthetic. I haven't driven anywhere yet, just started up and idled for a few moments. I can tell you the engine is running significantly smoother and quieter now. I wish I knew what exactly I drained out of the V10.

 

I'm a big fan of Rotella t6 5w40, my 250k silverado and my 175k Cherokee love the stuff.

I have to bit up the Bobistheoilguy forum to see what the consensus is for the modular engine.

 

According to the manual my 99 F350 calls for 10w30.