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Mixing Oils

jlevee

Geek
I am sure this question has been asked & answered many times over, but I did not see it in a search.

Over the years & oil changes i have wound up with all sorts of miscellaneous partial quarters of oils sitting around in my garage. 15w50, 20w50, synthetic, dino, etc. All of this has me wondering... is it safe to use different oils to top off so i can get rid of these? Like say is 15w50 safe to add to what is essentially a 10w40 oil change? what about adding a dino to a synthetic?
 
Don't think there is any harm mixing dino and synthetic. I mixed 50-50 10-30 Mobil 1 and Castrol 20-50 to make a 15-40 winter blend for my Ural. I just try not to stray too far from the recommended weights for the vehicle. But I always manage to use up leftovers by topping off the van or VW with whatever.
 
Oil is cheap...relatively speaking. And old oil sitting around can absorb contaminants that you might not want to put into an engine. On top of that, blending oil is done by engineers to achieve a specific additive package. There is little guarantee that such garage-blending will do any good...likely it could do harm. If you were needing some oil to get you another few miles down the road to a service station or an oil change or something, that might be OK. IMO, it's not good practice to use the oil up in this way in your bike. I wouldn't.
 
when you order bmw oil in the u.s. it comes in quarts

the bmw manual says to put in liters which have 6% more oil in them than quarts. if you want to make up the difference with what you got layin' around. i'd do it, which i already do (if i bother to do it at all).

i change the oil in the fall and halfway through the summer pretty much regardless of mileage. the filter only gets changed in the fall.

maybe if you use oil from fake dinosaurs, you might not wanna mix it with oil from real ones, although i doubt the effect on the engine could be quantified by a scientific scientist.

oh yeah, i got my first bmw in 1964. (i'm a lot younger than i look).

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Not sure about this comment, I quote; "old oil sitting around can absorb contaminants that you might not want to put into an engine." Where would these "contaminants" be absorbed from? Sure, an open container will collect debris and dirt, but not a sealed container.

If the oil is in the original container and capped, nothing can contaminate it. There is no problem in using oil "remnants" and the affects of blending minimal amounts of additives likely has little detriment to the used oil in the engine.
 
I don't consider these "sealed" containers all that very well sealed. The oil is going to absorb moisture (my opinion) and why would you put oil that already has moisture in it in an engine? There will be enough chance for the egine to do that all by itself...I see no reason for helping it along.

Dirty oil is better than no oil; clean oil is better than dirty oil. Just do what works for you. Me, I'll use the best clean oil I can find from a fresh container and recycle the rest.
 
Not sure about this comment, I quote; "old oil sitting around can absorb contaminants that you might not want to put into an engine." Where would these "contaminants" be absorbed from? Sure, an open container will collect debris and dirt, but not a sealed container.

If the oil is in the original container and capped, nothing can contaminate it. There is no problem in using oil "remnants" and the affects of blending minimal amounts of additives likely has little detriment to the used oil in the engine.

Thanks for a correct answer.:)
 
Not sure about this comment, I quote; "old oil sitting around can absorb contaminants that you might not want to put into an engine." Where would these "contaminants" be absorbed from? Sure, an open container will collect debris and dirt, but not a sealed container.

If the oil is in the original container and capped, nothing can contaminate it. There is no problem in using oil "remnants" and the affects of blending minimal amounts of additives likely has little detriment to the used oil in the engine.

I think you got it exactly right.
 
One way I get rid of a little oil left in the bottle is to put it into one of my "Squirt" type oil cans. It doesn't matter what weight it is or whether it is dino oil or synthetic, when you want to squirt some oil onto
something, it works.
 
The oil is going to absorb moisture (my opinion) and why would you put oil that already has moisture in it in an engine? ...............

Glad you qualified that statement as opinion, because it has NO basis on fact. Oil is hydroPHOBIC, not hygroSCOPIC. Oil, diesel, gasoline and most if not all petroleum products can be left in an open container and no water will be absorbed.

Glycols, and Alcohols on the other hand will absorb H2O

http://www.bio.brandeis.edu/classes/biochem104/hydrophobic_effect.pdf
 
I generally value the insights gained from this website based on the experiences of others but I really have a hard time when people voice their "opinion" but don't actually know what it is they're talking about as it creates confusion and substantially devalues the forum. So regarding the questions asked by the OP, let me make clear that in general oils are hygroscopic, that is they tend to absorb water moisture and so with time they will deteriorate. Also, with respect to the mixing of oils of different viscosities, I did find this on the Exxon-Mobil website, which is a source I'm more likely to trust than most people who have "opinions" which is just about everybody (URL: http://www.mobiloil.com/USA-English...arm_Mixing_Different_Mobil_1_Viscosities.aspx).

Glad I could help!

Kent
 
Glad you qualified that statement as opinion, because it has NO basis on fact. Oil is hydroPHOBIC, not hygroSCOPIC. Oil, diesel, gasoline and most if not all petroleum products can be left in an open container and no water will be absorbed.

der kaiser said:
let me make clear that in general oils are hygroscopic, that is they tend to absorb water moisture and so with time they will deteriorate.

Hmmm... :lurk Now I'm really confused!!

In the end, everyone can do what they want. I think it shortsighted to just combine oils for the sake of saving a few pennies or "finding some place to put the oil". Oil can easily be recycled. It's a critical element to an engine's health. If there is any doubt at all, I wouldn't do it. That just me...
 
Also, with respect to the mixing of oils of different viscosities, I did find this on the Exxon-Mobil website, which is a source I'm more likely to trust than most people who have "opinions" which is just about everybody (URL: http://www.mobiloil.com/USA-English...arm_Mixing_Different_Mobil_1_Viscosities.aspx).

Kent -

That website specifically states Mobil 1 viscosities. I wouldn't have any issue with using oils from the same manufacturer. But is it a universal truth that any oil, any viscosity, dino/synth can be mixed? I would doubt it.
 
Opinion #1: It won't kill you.

Opinion #2: If said oil were to have any moisture water in it (and I highly doubt it would), would it not evaporate the first time you went for a fully-warmed-up ride?

Opinion #3: If you're picky, do what RUDYJO does.

PFFOG: Reading that link and its chemical formulae gave me a headache. :laugh
 
Opinion #3: If you're picky, do what RUDYJO does.

I am picky on this topic; so I don't mix oils from different manufacturers, I don't let an open bottle stay around for very long, and readily recycle oil to my local autoparts store.
 
The best comment here is to go with what is comfortable for you. Again, some people regard internet info as gospel, other reserve a very restrained view of the info posted. At best, always do some research.

As to blending of oils per this comment: "But is it a universal truth that any oil, any viscosity, dino/synth can be mixed?"

Actually yes, for the most part. I have never read anywhere, in any of many oil articles and papers I've read, that Dino and Synthetic oils cannot be mixed. Same for viscosities. They can be mixed, but the mix will alter the final result of the effective viscosity. All depends on what you mix, and how much you mix in.
 
I appreciate al the information I have gotten. The reason I had not moved forward on using any of the extra oil i have is I did not think it would be smart/safe to do so. At this point I think I will just dispose of it.
 
Actually yes, for the most part. I have never read anywhere, in any of many oil articles and papers I've read, that Dino and Synthetic oils cannot be mixed. Same for viscosities. They can be mixed, but the mix will alter the final result of the effective viscosity. All depends on what you mix, and how much you mix in.

I think this is the point that I'm trying to make...sure mix away!! But what do you have in the end? Basically, it's an unknown, and if can do potential harm or give me a false sense of security, I don't want it in my engine. They pay people big bucks to blend oils for the manufacturers. I don't see how the average person can do as well...more than likely it will be worse.
 
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