Some people say never to mix different brands of oils because the different additives can react in bad ways, but I have never seen any evidence or proof of this. I've used various HDEOs in the same engine depending on what was available, and have never noticed any obvious problems at drain time. In fact, I've seen some supposed experts recommend things like mixing synthetic and dino 50/50 to make a semi-syn home brew. Has anybody on BITOG evidence that mixing oils is bad business? I'm thinking of similar oils, like in 15w-40 mixing Delvac, Delo, and Rotella, for example.
Mixing HDEOs?
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why would someone want to mix in the first place? I doubt anything bad will happen mixing. Aren't all oil compatible
Originally Posted By: AuthorEditor
Some people say never to mix different brands of oils because the different additives can react in bad ways
It's not that the two oils will react badly. It's that they won't be at their best.
In other words, it's not going to blow up your engine. It just probably won't be as good as one good oil on its own.
Some people say never to mix different brands of oils because the different additives can react in bad ways
It's not that the two oils will react badly. It's that they won't be at their best.
In other words, it's not going to blow up your engine. It just probably won't be as good as one good oil on its own.
All the oils are compatible. The stronger oil gets weaker and the weaker oil sets stronger. There usually is no gain by mixing oils.
One reason to mix is availability and price. For example, right now Delvac is on sale at WalMart for $9.50. Even though I've got Delo in there I could see buying some Delvac and saving a few bucks, but maybe Rotella would be cheaper at the next OCI. So I might end up with Delo in the engine but nothing but Delvac or Rotella for make up oil. At the next change I might have one gallon of Delvac and one of Delo. Or if I'm traveling somewhere on a long trip I might have to buy whatever oil is available locally. This is actually what I've done over the years with no apparent problems.
From talking with my oil supplier, the classifications on the HDEO oils (CJ-4, CI-4+, etc) make the various brands so close as to not be an issue. I would have no problem mixing HDEO that within the same classification. Might not be the greatest idea from a purely technical viewpoint, but in the real world I don't think it would be a problem.
dnewton3
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There are a few reasons one might "mix" oils.
1) necessity
2) desire
3) inadvertent
There is no terrible oil chemistry accident waiting to happen if you mix brands of similar grades/specs. That's an old myth that seems to have resurfaced recently. One of the main points of API certification is the ability to assure lubricant compatibility. Using a CJ-4 with a different CJ-4 is about as compatible as you can get from different sources.
If you mix a CJ-4 Delo 15w-40 with a CI-4 10w-30 Rotella, you'll end up with some hybrid viscosity and additive package that confounds the AR Bitog'er. But there is no reason to expect it will create some massive clash of molecules that results in abrasive tar ... Mixing compatible oils will never hurt your engine, as long as you stay in a reasonable grade and the add-pack is not grossly outside the realm of "normal" to the equipment OEM. Since CJ-4 fluids are backwards compatible, there's really no risk here at all.
You can even mix a non-detergent 30 grade with a 5w-20 PCMO. There is little reason to expect the oil will self-consume and subsequently auto-ignite in a fireball. It will make the lube unworthy of long term use, though. Is this advisable? Depends upon how desperate (or adventurous) you are. If I were in the middle of nowhere, and my low oil level light came on, and I needed VOLUME to simply get the oil level up to a safe point, I'd use just about anything to get me home until a proper OCI could be done. There is little very risk in short term exposures, even using the "wrong" oil. I've also been known to mix brands/grades when topping off a low-tech ol' skool valve-in-block B&S engine. But the risk is low there for such splash lube engines.
My point is that mixing is like everything else. You may HAVE to do it to get home. So do it and don't worry about it. Or, you may be mixing to clean up some left-overs from the garage. Either is ok. The important thing to note is that short term mixes can be done with about anything. But long term mixes need to be with compatible fluids.
One important thing to note; mixing will, however, distort your UOAs. If that's not a concern to you, mix away.
1) necessity
2) desire
3) inadvertent
There is no terrible oil chemistry accident waiting to happen if you mix brands of similar grades/specs. That's an old myth that seems to have resurfaced recently. One of the main points of API certification is the ability to assure lubricant compatibility. Using a CJ-4 with a different CJ-4 is about as compatible as you can get from different sources.
If you mix a CJ-4 Delo 15w-40 with a CI-4 10w-30 Rotella, you'll end up with some hybrid viscosity and additive package that confounds the AR Bitog'er. But there is no reason to expect it will create some massive clash of molecules that results in abrasive tar ... Mixing compatible oils will never hurt your engine, as long as you stay in a reasonable grade and the add-pack is not grossly outside the realm of "normal" to the equipment OEM. Since CJ-4 fluids are backwards compatible, there's really no risk here at all.
You can even mix a non-detergent 30 grade with a 5w-20 PCMO. There is little reason to expect the oil will self-consume and subsequently auto-ignite in a fireball. It will make the lube unworthy of long term use, though. Is this advisable? Depends upon how desperate (or adventurous) you are. If I were in the middle of nowhere, and my low oil level light came on, and I needed VOLUME to simply get the oil level up to a safe point, I'd use just about anything to get me home until a proper OCI could be done. There is little very risk in short term exposures, even using the "wrong" oil. I've also been known to mix brands/grades when topping off a low-tech ol' skool valve-in-block B&S engine. But the risk is low there for such splash lube engines.
My point is that mixing is like everything else. You may HAVE to do it to get home. So do it and don't worry about it. Or, you may be mixing to clean up some left-overs from the garage. Either is ok. The important thing to note is that short term mixes can be done with about anything. But long term mixes need to be with compatible fluids.
One important thing to note; mixing will, however, distort your UOAs. If that's not a concern to you, mix away.
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