I have an 05 Superduty with a 6.0 diesel engine that I have been using various synthetic oils for, for quite a few years now. I also have an 74 F250 with a rebuilt 460 gasoline engine that needs an oil change. The 74 probably has 5 or 6 thousand miles on that rebuilt engine.

I have several partial gallon bottles of synthetic oils, i.e. Delo full syn 5-40, Mobil 1 turbo diesel truck full syn 5-40 and a few bottles of Rotella T6 full syn 5-40. My question is, is it safe to use this oil up in my old F250 460 engine? I don't want to mix oils in the 6.0 diesel because those are such meticulous engines that I'd be worried about very expensive repairs as a consequence. My thinking is that the 460 engine is much more forgiving, yet I don't want to mess that one up either. Anyone know of a reason not to use and mix these oils for that gas engine?

 

There's a popular oil forum online and guys mix oils all the time there. They even do a used oil analysis on the blend. I've even seen different SAE rated oils mixed. But not sure about diesel oils (I can only remember oils intended for gas engines) and I have no idea what the 460 is rated for.

In my one-person, not-a-chemist opinion, if the 460 can handle that rating of oil I don't see any issues by mixing different brands. It will all blend together. But if you're not sure, just recycle it or sell it. I personally wouldn't blend even common weight oils in modern engines, but I'm Type A like that...But I'd do it in a nice old 460.

 

Lots of unknowns.

In general, best Not to mix different Brands of oil, so as not to have base oil, or ad pack interaction possibilities.

Since we don't know what synthetic base oils are used in different brands, or in what concentration, or what is in the ad packs, or in what concentration, no way to determine how close to the saturation point the base oils are in with any additive & if mixing brands would cause over saturation & have additives fall out of suspension & cause other mischief.

Or if the concentration of synthetic base oils & their ad pack may have any unwanted action on the older engine seals, or gaskets.

If your bound to use what you have, consider mixing the oil of the same Brand & determine if it's dual rated = gasoline/diesel & if rated to be ok to use in a gasoline engine, is it's service grade also back specified to cover the 74 engine call out for service grade & hot/100c viscosity requirement for the engine, in the environment & drive cycle it'll be subjected to during the oci.

This way engine seal & gasket compatibility & the base oils & ad pack, will be more likely compatible.

If in doubt, as has been suggested, sell it, or give it away to Goodwill, so they can sell it to someone that can put it to good use.

More thoughts for consideration let us know what you decide to do & how it goes.

 

If it were me I'd save all of the partial oils for my next double engine flush. Why pour in new oil and waste it...

 

“Additives are blended at the proper rate, heat and in the proper proportions by the manufactures of their particular product. Crude supplies are not all the same quality and the additives have to be adjusted for the quality of the base stock being used by each particular company, per batch. Dumping your own personal stuff will more than likely be way inferior to what the oil manufacturer uses. The chemicals will normally differ from the manufacturers blend, and can cancel each other out to the point where there will be no anti-wear properties left in the product. (This is one reason it's not wise to mix oils from different manufacturers together). Changing the oil from say Mobil to Shell and then to Pennzoil will have a negative effect on your engine from conflicting chemicals. Buy an oil that you may like and STICK TO THAT COMPANY'S product.”

“What you may get away with when using Shell may cause instant havoc with Valvoline. The major oil companies work closely with the auto manufacturers so that bearing material, seal material, roller bearings, ball bearings, and all other moving parts are not adversely affected by the oil products. This is especially true for automatic transmissions. DO NOT USE SOMETHING OTHER THAN WHAT IS SPECIFIED BY THE CAR MAKER FOR YOUR AUTOMATIC TRANSMISSION”


Read more: Car Bibles : The Engine Oil Bible : Additives

Read more: Car Bibles : The Engine Oil Bible : Additives

 

Sorry, but that is nonsense.

I am not advocating mixing jugs of oil together, but you do not have to pick one specific brand and use it for the life of the truck.

Use whatever is on sale at the time you need to change your oil. If that is PZ one time and Valvoline the next time, you are not going to harm your engine. To suggest otherwise is marketing BS.

 

FYI- if you check out the quals of the person at the link, they are a credentialed engineer (lubrication industry)....my own dad who was by trade a mechanical engineer (aerospace) drove this home to me from the time I was old enough to hold a wrench in my hand....but I understand and respect what you are saying as well.

 

Edited Version: Funny, there's a big rant over at BITOG right now about mixing oil and how it's a bad idea. Guess my earlier suggestion needed more vetting. But that's how the internet goes.

 

You are suggesting that engineers do not engage in marketing. Having sat in hundreds of meeting involving R&D engineers and marketing guys, I know this not to be true.

As far as your father, I am sure that he is/was a fine man and I mean no disrespect, but we all buy into marketing shinola from time to time.

What I know is that I have used (and so did my father) whatever oil was on sale at the time in hundreds of cars for decades and neither I, nor my father, have ever had a oil related engine problem.

Also, are you sure that your local Quikie Lube, or even your local dealer, always uses the same brand of oil, month after month, year after year?

Having said all that, personally, I use Wally SuperTech pretty consistently because it is usually the cheapest.

 

After Re-reading the OP's initial post & thinking about this some more, seeing as how they're various Opened gallon containers of Synthetic & not knowing How or long, or under what conditions they've been stored, ie Humidity, nor how well resealed they've been, maybe also consider this info https://www.ford-trucks.com/forums/1...ubricants.html, in deciding what to do with it.

Since they're opened containers, I suppose the Goodwill option isn't valid.

 

No, but I am saying, and my father was the engineer who designed the hydraulics system on Pioneer (we have the the test data and the test chamber pics taken at STL in Santa Barbara, Ca) and other space vehicles and whose engines (he was part of the "Thunder Alley or Thunder Road" group in Los Angeles- this included Vic Edelbrock Sr, Dick Guldstrand, etc.) whose engines turned 211 mph at El Mirage back in 1955 (a streamliner driven by the youngest of the Stecker Brothers)....non of whom ever promoted this either. Yes, in today's world, its amazing how many people will "sell themselves" for a few $'s or self promotion, but, when you look at the pioneers of our aerospace programs whose standards and philosophies are the scientific principles that we function from today, although not totally exempt, when an engineer spoke publicly or transferred information down, it was for the right reasons.

and let's face it.......the term synthetic oil was determined by the courts years ago in a mega lawsuit to refer to additives that provide a certain level or type of lubrication, not the base oil being a synthetic...........

 

As I said, I have no reason to disparage your father.

But if anyone has any data to support the proposition that once PZ brand oil (for example) touches the dipstick, then you should never run any other brand of oil, I want to see it.

Sorry, but the whole concept smacks of marketing hype.

As I said, I have owned 100s of cars over decades and used whatever oil was on sale and have never had an oil related problem.

And that is not something that my father told me, it is my own experience.

 

it's simple..............basic chemistry......as crude oil is heated, it comes from a variety of sources, it's heated to form oil, heated higher to form gasoline, heated higher to form propane (base product), then based upon a variety of conditions, including chemical analysis of the "base" product, additives are varied to create the required product outcome....

as an example, 90% of the oil produced in SoCal is exported to foreign countries, the gulf, processes most of it's oil for the US there.....Texas, the Chevron refinery there is (IIRR) the only refinery to stipulate they produce synthetic base oil.........

The oil that comes from the ground in SoCal, will have a different structure than that which is extracted in texas or florida......just like drinking water.....it doesn't all tast the same because the chemistry property is different at each well, requiring different purification processes (although similar, different)

 

Lets stay on the OP's original subject question, about mixing various brands of Opened gallon containers of synthetic 5W-40, that he'd been using in his 05 6.0L diesel but doesn't want to use a mix in it, so he's thinking maybe he could use it up in a rebuilt 74 F-250 460 gas engine.

Seeing as how it seems the oil has been opened & setting around for an unknown time & stored in an unknown temp & humidity environment, before use, it seems to me separation & additive drop out possibilities, ect, should also be taken into consideration.

SO, before using, a good warming up & shaking to remix things that might have separated, or dropped out of suspension might be considered.

 

A nice statement of the obvious. but does not even attempt to answer my question. If anything. it supports it.

Oil comes out of the ground all over the world. Oil from many, many sources and countries is also refined all over the USA. There is no guarantee that the Delvac 1300 that I buy this week came from the same well or the same refinery as the oil that I bought 1 year ago.

So there is no guarantee that even if I buy the same brand and weight of oil, over time, the chemistry is exactly the same.