I own a 2011 F-350 king ranch that only has 14,700 miles on it mostly pulling my 42 ft 5th wheel. I have been using rotella T6 full synthetic oil in it since the first oil change. Does synthetic oil break down over time or can it be left in until it reaches it's mileage limit. I normally only put about 3-4 thousand miles on the truck each year. I have called several dealerships with this question and gotten a variety of answers.Any feedback would be greatly appreciated. Thanks

 

Much like gasoline, motor oil degrades because of the hydrocarbons in the product. Synthetic motor oil isn't actually 100% synthetic; it still has petroleum products in it, which means hydrocarbons.

I don't know to what extent it will degrade, or how long it'll take, but it will get "funky" after awhile.

Typically, it's a good idea to change the oil at the mileage limit, or at a six month interval, whichever comes first.

 

Hi Kingranch, welcome to FTE!

Your diesel supplement says the change interval can be up to 10,000 miles or 1 year. I would change it at least yearly.

 

A 6.7L can be $20k+ to replace an engine assembly, why skimp on $100 in oil once a year? Over the life of my truck I've spent maybe $2,500 on doing oil changes every 5k instead of the 7.5k per the book, and easily $20,000+ on fuel. Not that big a cost over 8 years.

 

Oil is basically the lifeblood of any engine. A DIY oil change is 60 - 80 bucks plus fuel filters for another 30 - 40 dollars, at a service facility, not too much more. I don't put too many miles on mine per year either, but think a spring and late fall/early winter change is well worth those few bucks. Rotella and several others meet the Ford spec and that's all you really need to really concern yourself over as far as oil breakdown. I use Motorcraft oil and filters in my truck and Rotella and Purolator filters in my diesel powered tractor and both do well. Of course, others will have varying opinions and what makes this sooooo much fun

 

I would go with a yearly change even though you aren't putting very many miles on it. I also wouldn't use synthetic either, but that is just a personal preference. I have put over a million miles on diesels in the past 5 years using conventional Rotella T with no issues at all and it costs a lot less.

 

Thanks for the feedback guys, I believe I will go with yearly oil changes then, but still stick with synthetic.

 

Once a year is fine. Mileage is far more important than time.
Probably even more important though is the load on the engine. Obviously your 14 k miles is harder than someone not towing as often or as much. Should that mean an increase in changes? Up to u. I think you will be ok with yearly ...or start of winter/summer. If you wish to keep things optimum

 

dont do it i used syn oil and it blew my injectors oil seals in 2, 5, 6, 8, stay with convent oil

 

Oh please elaborate.

At NO time is conventional better than synthetic. Never.

Under super hot stress conditions like a race car engine..20w 50 does good protection with conventional.

That is the only example of a time when conventional is close to synthetic from a performance point of view.

Outside of that zero. In the cold? It's not even remotely close comparable.

Go synthetic and enjoy.

 

there are lots of times that conventional oil is a better choice. Synthetic oil ONLY refers to the base stock. Has nothing to do with the additive package. The correct conv oil with a good additive pack will preform better than a syn with the wrong or bad additive pack. keeping the additive pack fresh is important and a good reason to change oil, I am NOT anti syn. I use them in many applications, but each application is different. If the cost of the syn oil prevents you from changing the oil when it should be changed conv would be better. There are just as many high mile engines with conv oil than ones running syn. the choice is up to you. If you operate in extreme cold or heat syn might be a good choice

 

Bobv....
#1 I made no mention of price. If cost of concern in all reality I would have to ask how did you acquire an expensive piece of equipment that is not cheap to run in the first place....but yet one can't afford synthetic? Ok.

#2 I made no statement that conventional is garbage. But it is not on the same level as synthetic except in a few very rare cases.

#3 additive packs? All that? Wow. Not going to entertain that. We are talking about oil for the crankcase here not the next lunar missile off to mars.
The normal brands are up to snuff and if not go to the next one.
I would still like to hear where conventional is better than synthetic in the real world engines we run.
Price does not count here. Additives? Well I guess if you can find that rare synthetic example that does not meet requirements...I'm sure I can find a conventional brand likewise. So that is a wash. All things being equal, and price irrelevant since we are talking of performance there is no example of conventional oil better than synthetic. None. Btw, heat is the one area where certain conventional can come close to synthetic. 20w 50 is about it. That is the only time conventional is in the same ball park.

 

there are times and places for synthetic and conventional oil.
i would much prefer to have a fully synthetic oil in any HEUI engine, or really any equipment that needs to work hard, and keep working.
poorly running HEUI engines can smooth out, just from changing to synthetic oil.

on the other hand, for running around and getting groceries in your civic, conventional oil is all you need.

when it comes down to it, conventional oil is easier to break down, doesn't take heat as well, and also is not as good at dissipating heat either.


if you can afford synthetic, then get it. why not?

 

If you have ANY concerns, stay with the oil the manufacturer recommends and uses. I've used both and tend to stay with the usual Motorcraft diesel blend, but there for sure is no reason that a good synthetic oil wont work just as well. As far as that being the cause of wrecking injectors - nahhh. You had another pressure related problem that your mechanic cured.

 

Kingranch,

I have a 2006 KingRanch w/a 6.0 Diesel which sits a lot, takes mostly short trips except when pulling the 5'er & have spent a lot of time/money on this very question so maybe I can help here

It takes me about 16 Months to get 5,000 Miles on my Truck & I too use Rotella T6, now before everyone says u must follow a 9 year old book & change the Oil every 12 months, think about the advances in modern Oil.

I have been doing this for quite some time & sending an oil sample to BlackStone Labs after every oil change. They continue to tell me to run the oil longer (which I don't run longer than 5k) because the TBN reading stays strong @ 5.6-8.1

The TBN only needs to be greater than 1 to protect your Engine adequately & if I can run nearly 1.5 years (5,000 miles) between changes & the Oil still has better protection properties than most Oil's right outta the jug, than Rotella T6 proves itself to me