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#190772 - 05/15/06 06:27 PM mixing motor oil brands
sxg6 Offline


Registered: 05/23/04
Posts: 2163
Loc: CT
Am i correct when i say you can mix different motor oil brands? you can mix different api service classes (sm, sl), you can mix dino, blend, and synthetic. as well as different weights

there is a discussion on another forum i visit about how ...

"30+ year chemical engineer and tribologist (do you need to google what a tribologist is?) who's entire career has been nothing but automotive oil says:

"if you mix oils, mix oils of the same brand as some addatives between the companies are incompatible"

Guess who I'm going to listen to. kthxbye

Unless of course you can provide credentials showing you know more about automotive oil than he does.

Dont mix oils from different manufacturers. the addin packs and addatives can be incompatible, causing the oil not to protect properly."


can you or can you not combine pcmo's without any problems.

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#190773 - 05/15/06 06:56 PM Re: mixing motor oil brands
beanoil Offline


Registered: 10/17/04
Posts: 1962
Loc: Midwest, Illinois
Ohhhhhh noooooo! Now my dog will leave home, my wife will cheat on me, and my engine will probably just sputter to a stop during rush hour. What do you think happens when someone grabs a quart of ______________ and puts it in their car after ______________ or ______________ has changed their oil, and used ___________? ( You can fill in the blanks) Although I lean toward the "safe" side when blending, and usually stay within brands, there is NO harm to cross brand blending, in my experience, and in fact there are several great UOA where Redline has been used to spike a conventional oil. My most recent blend was a 50/50 of Havoline 5-20, and Delo straight 30. Not too odd, most would say. Except, the Hav was an Equilon product from the Shell Texaco venture, not even close to being in "the circle of trust" with the current Chevron offering. No problems with this brew, and the best highway fuel mileage to date. Blend on master mixologist.

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#190774 - 05/15/06 07:13 PM Re: mixing motor oil brands
surfstar Offline


Registered: 09/16/04
Posts: 4285
Loc: Santa Barbara, CA
quote:
Originally posted by sxg6:
Dont mix oils from different manufacturers. the addin packs and addatives can be incompatible, causing the oil not to protect properly.

The operative word here is can. There's a chance it could happen, but he didn't use "will".

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#190775 - 05/15/06 07:24 PM Re: mixing motor oil brands
sxg6 Offline


Registered: 05/23/04
Posts: 2163
Loc: CT
what exactly would happen then? what additives could clash and cause the oil to not protect properly?

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#190776 - 05/15/06 07:34 PM Re: mixing motor oil brands
Blue99 Offline


Registered: 09/27/03
Posts: 2233
Loc: Wisconsin
quote:
Dont mix oils from different manufacturers. the addin packs and addatives can be incompatible, causing the oil not to protect properly."

My comment is that when mixing brands, the mixed brew may have a reduced performance level as compared to either of the two component oils.

I can think of a couple of witch's brew reports in the UOA forum where 3 or more oils were mixed and the wear metal results were basically average for that particular engine/vehicle.

So while the mixed brew may have a reduced capability for a particular additive performance characteristic, this generally does not translate into any significant engine wear over a moderate 3-4K OCI.

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#190777 - 05/15/06 08:47 PM Re: mixing motor oil brands
hominid7 Offline


Registered: 08/10/05
Posts: 1523
Loc: North Texas
quote:
Originally posted by Blue99:
My comment is that when mixing brands, the mixed brew may have a reduced performance level as compared to either of the two component oils.
<snip>
So while the mixed brew may have a reduced capability for a particular additive performance characteristic, this generally does not translate into any significant engine wear over a moderate 3-4K OCI.

I would tend to agree. In addition when mixing oils i think it is important to follow the oil change interval relavent to the lowest factor involved. In other words, i would not think adding 1 quart of Mobil1 to my dino oil means i can then wait 10K miles to change my oil.

Some people have had positive results with their mixing experiments, there is no doubt about that, but I would not want to do it as there are too many unknowns.

While I would prefer to keep everything all the same, if given no other choice i would rather mix in a quart of Big Billy Bobs Trucker Special Oil rather than run my car low on oil for any period of time.

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#190778 - 05/16/06 09:56 AM Re: mixing motor oil brands
bighead Offline


Registered: 03/17/05
Posts: 846
Loc: NCAA National Football Champs ...
Sooo, then if I have a gallon of Exxon Superflo, and will be short either half or whole quart (depending on which vehicle it goes in), then I shouldn't top up with something else? I have Pennzoil, Havoline, and Castrol GTX in my stash, and have exactly enough for 4 changes for each vehicle. I would rather not have to buy a single quart of anything, as neither car uses oil, and I'll end up with a half quart of something just lying around...

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#190779 - 05/15/06 10:08 PM Re: mixing motor oil brands
TomJones76 Offline


Registered: 11/06/03
Posts: 1250
Loc: Akron, OH
sxg6:

Your quote has it right.
There is a *small* chance of additive clash that would result in a multibrand blended oil (MBO) being dramatically worse than either of its parent oils (***).
I say small, because with all the insane blends the people on here are doing, if it was likely to cause a problem very often, I can think of 5 posters here who'd be walking to work.
I had an OK UOA running a mix of Pennzoil, Supertech, Rislone and GC one time.

There is a substantial chance that creating an MBO will create an oil that's just not as good as any of its ***.
Think of pharmaceuticals. 200 MG of Drugium may prevent seizures in a given patient, while 100 MG won't. Meanwhile, 400 MG of Noflopium will stop seizures for this patient, but 200 MG won't really cut it.
What happens if the doctor decides to give the patient 100 MG of Drugium and 200 MG of Noflopium?
Unless someone has tested this combination:
I don't know.
You don't know.
The doctor doesn't know.
The pharmaceutical company [oil company by analogy] doesn't know.
Maybe the blend has BETTER anticonvulsant properties that either Drugium or Noflopium had separately.
Maybe it works about the same.
Maybe it does nothing at all to prevent seizures, or a lot less.

Let's say the minimum effective level of Noflopium in the blood consists of what you'd get from 250 MG.
If you're given 400 MG, imagine your body will burn through 5 MG per hour. After 24 hours, you'll have the equivalent concentration of Noflopium in your system as what you'd get from 260 MG.
Okay, good, you're not having seizures driving around in your Dodge RAM.
You pop another Noflopium, and your levels inflate back above 400 MG, and you'll be good for another day.
I'm oversimplifying medicine half-lives here, but this is just an analogy.

Let's take that back to cars.
You could mix two *** that would experience anti-wear (AW) additive depletion separate from one another at 10,000 miles and wind up with an oil that will experience additive depletion at 5,500 miles. One oil might used a heavy Zinc-Phosphorous formulation, while another uses one of those fancy-pants formulas that's relies heavily on Antimony and somewhat on small levels of Zinc-Phosphorous to provide AW protection.
Where either PO would have been hosed individually at 10K, now you're at 5500 and your Antimony levels are pathetic and your Zinc-Phosphorous is way down too.

I run intervals from 5K and up in my car and drive 18K per year, so I keep it all one brand.
My wife changes out every 3 months (1500 miles in her case) and drives 6K per year, so I just stick whatever 5W30 I have sitting around spare (but clean) in the garage in her car.

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#190780 - 05/15/06 10:09 PM Re: mixing motor oil brands
TomJones76 Offline


Registered: 11/06/03
Posts: 1250
Loc: Akron, OH
Wow. The board just censored P O s. As in, plural of PO, standing for parent oil. Just to clarify my post here....

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#190781 - 05/15/06 10:11 PM Re: mixing motor oil brands
TomJones76 Offline


Registered: 11/06/03
Posts: 1250
Loc: Akron, OH
quote:
Originally posted by bighead:
Sooo, then if I have a gallon of Exxon Superflo, and will be short either half or whole quart (depending on which vehicle it goes in), then I shouldn't top up with something else? I have Pennzoil, Havoline, and Castrol GTX in my stash, and have exactly enough for 4 changes for each vehicle. I would rather not have to buy a single quart of anything, as neither car uses oil, and I'll end up with a half quart of something just lying around...

I'd go ahead and buy the extra quart, just to make the used oil analysis easier to interpret, unless it's my wife's Neon, which my wife doesn't really WANT to live any longer.

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#190782 - 05/15/06 10:13 PM Re: mixing motor oil brands
thooks Offline


Registered: 11/30/05
Posts: 692
Loc: Marietta, GA
I'm running 3 quarts of Havoline and 2 quarts of M1 in my 95 Accord right now.

It will stay in there for another 4,000 miles.


I have no worries.

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#190783 - 05/15/06 10:19 PM Re: mixing motor oil brands
TomJones76 Offline


Registered: 11/06/03
Posts: 1250
Loc: Akron, OH
quote:
Originally posted by sxg6:
what exactly would happen then? what additives could clash and cause the oil to not protect properly?

One Usenet post I read a decade ago had a Shell tribologist (posting on what appeared to be his real name) claiming that two common synthetic 5W30s he named (forget which) would have an additive reaction resulting in a 15W40 viscosity.
Take that for what it's worth, which I suspect is about the price of one first-class stamp in 1993.

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#190784 - 05/15/06 11:23 PM Re: mixing motor oil brands
hominid7 Offline


Registered: 08/10/05
Posts: 1523
Loc: North Texas
quote:
Originally posted by bighead:
Sooo, then if I have a gallon of Exxon Superflo, and will be short either half or whole quart (depending on which vehicle it goes in), then I shouldn't top up with something else? I have Pennzoil, Havoline, and Castrol GTX in my stash, and have exactly enough for 4 changes for each vehicle. I would rather not have to buy a single quart of anything, as neither car uses oil, and I'll end up with a half quart of something just lying around...

Pennzoil and Havoline should be pretty mix-friendly as their anti-wear agents are similar. Superflo should also be, although it has less moly i believe, and thats why of the three it's the one i would rather mix with Castrol.

So in your case, if you wanted to just buy one additional "top up" bottle, i'd go with the Superflo.

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#190785 - 05/16/06 01:22 AM Re: mixing motor oil brands
LT4 Vette Offline


Registered: 09/12/04
Posts: 12103
Loc: USA
Mix all the oils you have, no harm will be done.

I got a Citgo, Castrol GTX and Delo SAE 30 mix in my wifes Honda......and the engine PURR's like a kitten.

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#190786 - 05/16/06 01:53 AM Re: mixing motor oil brands
bighead Offline


Registered: 03/17/05
Posts: 846
Loc: NCAA National Football Champs ...
quote:
Originally posted by hominid7:
quote:
Originally posted by bighead:
Sooo, then if I have a gallon of Exxon Superflo, and will be short either half or whole quart (depending on which vehicle it goes in), then I shouldn't top up with something else? I have Pennzoil, Havoline, and Castrol GTX in my stash, and have exactly enough for 4 changes for each vehicle. I would rather not have to buy a single quart of anything, as neither car uses oil, and I'll end up with a half quart of something just lying around...

Pennzoil and Havoline should be pretty mix-friendly as their anti-wear agents are similar. Superflo should also be, although it has less moly i believe, and thats why of the three it's the one i would rather mix with Castrol.

So in your case, if you wanted to just buy one additional "top up" bottle, i'd go with the Superflo.

Well, I have (1) 1 gallon jug of Superflo and (1) 5qt jug of the GTX, so I'd have a half qt left of the GTX because my car has 4.5 qt sump. So you're saying the leftover .5 qt of GTX would be good to add to the 4 qt's of Superflo for the next change.....I gotcha. Thanks.

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