Mixing oil types...

Joined
Apr 19, 2009
Messages
60
Location
Cleveland, OH USA
Hi all, I've done some reading, but haven't quite figured this out yet. I have an 01 Sentra with 50k on it. I switched to synthetic last year with no issues. It's a bit hard to keep up on what is a true synthetic and what is not, but what I really want to know is if it matters where mixing of synthetic types is concerned. I've read that a true synthetic should not be mixed with mineral, but what about a true synthetic with other synthetics that might be a blend or a different group number? On car bible it implied that Mobil1 may not be suitable for mixing because it was derived from something different than the others. I don't know how old that page is though and I know that Mobil1 now isn't a true synthetic, but I don't know if it was when I bought it. Should I have done a flush before I switched? I always research and at the time the info I found seemed to indicate I didn't have to since I had low mileage and the car was well maintained. I have Valvoline Synthetic in their now. I believe Synpower. Thanks
 
Joined
Sep 8, 2005
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15,234
Location
Canada
You can mix any oil with any other oil. They have to be compatible to pass the SL/SM spec. It doesn't do any harm; its really a non-issue. You don't have to 'flush' and engine to switch; you can switch back-and forth at will. It may have been an issue in the early days of synthetic oil, but that was 30-35 years ago.
 
Joined
Dec 26, 2006
Messages
1,648
Location
Little Rock, AR
No problem whatsoever (from my reading of statements from the Oil companies on this issue). But it's not a good idea to go on mixing different oil types - each oil is holistically designed, and your messing with that design and likely ending up with a lesser oil.
 
Joined
Oct 21, 2005
Messages
703
Location
Northwest Indiana
 Originally Posted By: D189379
I'll be mixing up a 5 different quart concoction on Saturday for my truck. Should be fun.
Ive done the Franken-mix before too, when Ive had odd-quarts laying around and had no problems of any kind.
 
Joined
Jul 22, 2007
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674
Location
Nebraska
I plan on using up some of my left over quarts this weekend. My truck calls for 5w30 I plan on using: 3qt Quaker State 5w30 conv. 1qt Penz YB 5w20 conv 1.6qt Quaker State Q Horspower 5w30 synthetic. I dont think there is anything wrong with it. As long as you meet standards it should be fine.
 

JHZR2

Staff member
Joined
Dec 14, 2002
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All oils are miscible with all other oils. At a time, there was the potential for "additive clash" where the chemistries competed with/against each other instead of for the surfaces, and thus would sometimes come out of solution. Some adds need/needed some non-synthetic base oil to aid in solubility, but there have been no issues as of late that I know of. As a general rule, perhaps obsolete, but safe none the less is that if mixing oils, try to keep them from the same manufacturer. This minimizes the chance of incompatible chemistries of various sorts. Folks have often also talked of doing a quick interval if moving to syn long-term, as this gets the remnants of conventional oil out, while setting up the surfaces with the new add packs. I think this is sound, but how necessary? I can't cite any real sources, though I think some have claimed M1 perhaps made this a suggestion some time back.
 
Joined
Apr 17, 2006
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Lake Forest, CA
 Originally Posted By: JHZR2
... As a general rule, perhaps obsolete, but safe none the less is that if mixing oils, try to keep them from the same manufacturer. This minimizes the chance of incompatible chemistries of various sorts...
I agreed. I mixed the same brand, same type but different weights, i.e., M1 with M1, Mobil 5000 with Mobil 5000 ...
 
Joined
Apr 5, 2009
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CA.
I plan on doing a mix of YB and Pennzoil HM oil at my next OC. I have a few qts of each but not enough for one full OC. I don't anticipate any problems. I also feel that mixing lets say YB with PP would give a better synthetic blend than I can buy off the shelf. I would have complete control of the percentages of each. I think keeping it to the same brand is a good idea, but doubt it would cause any problems not doing that. I have few buddies that add RL oil to their favorite Dino oil to tweak the dino oil. There are a lot of closet chemists, many remain in the closet though for fear of getting flamed on BITOG. AD
 
Joined
Jun 17, 2005
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4,942
Location
Billings, MT
I have the following mix in my moms car right now. 1 quart each of: Mobil 1 10W-30 Extended Performance Mobil 1 10W-30 Quaker State Torque Power 5W-30 synthetic Super Tech 5W-30 synthetic Valvoline Synpower 5W-30 Motorcraft 5w-20 synthetic blend It all mixed fine. The car runs great, with absolutely no signs that there are any problems. If I felt like wasting the $, I could do a UOA when it has 6K miles on it to see if it really is doing fine.
 
Joined
Jun 17, 2005
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Billings, MT
 Originally Posted By: ADFD1
I think keeping it to the same brand is a good idea, but doubt it would cause any problems not doing that.
That's just the thing, being the same brand does not mean they use the same additives, or even the same additive supplier.
 
Joined
Jan 2, 2008
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PA
Looking at VOA and UOA it seems as it everyone is using the same type of additive ingredients but amounts may vary. If you can mix group 1,2,3,4 and 5 oil it would stand to reason that relatively similar additives would mix as well. The only situation where that may not be the case could be in specific additives used in race or specific purpose oils.
 
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