Mixed Oil Debate

[OVERKILL]

The API ensures that oils of the same API spec are compatible with each. If mid-way through your OCI you’re down a quart of oil and you don’t know what brand of oil the shop used, do you really think you’re causing harm by pouring a quart of oil that’s a different brand? I mean come on now. I’ve never heard of any motor oil company say you can’t mix with other brands. The only thing I’ve read from motor oil companies remotely regarding this is if you are using an extended mileage formula. Extended mileage formulations such as, Mobil 1 extended performance, Castrol Edge extended performance, and Amsoil Signature Series, cannot guarantee the long drain interval if topping off with a different motor oil.

Which brings me to another point. Pennzoil has a new oil called Pennzoil Top Off Oil. It was mentioned here once and I saw it on the Shell product guide about a week ago. Do you think Pennzoil is going to market something that is going to cause some sort of chemical imbalance?

No they don't, please see my reply above. The miscibility standard appears to be widely mischaracterized.

ASTM D6922, from here: https://www.api.org/-/media/Files/C...hash=C16D3A3F94222F002EB3A1C9AC45BE19AC52ECA6
Denotes:
- Shall remain homogenous and, when mixed with ASTM reference oils, shall remain miscible:

That's all it promises.

The test:

ASTM D6922​

Apparatus for the determination of homogeneity and miscibility in automotive engine oils. It is important that engine oils from different manufacturers be homogenous and miscible with each other, because operators of automotive engines often do not have prior knowledge of the manufacture of the oil that is currently used in their application, and engine failure can occur if oils are combined that do not stay homogenous and function properly. For this test method visual color determinations and observations are made on an undiluted test oil specimen, along with six blends of the same test oil that have been combined with specific reference oils at room temperature after the samples have been preheated to 46°C in a TC16 liquid bath. Then manually (as this is the referee method), the pour point of the samples is determined using single and adjustable Tamson TLC40-14(s) and/or TLC80-14(s).

They aren't mixing M1 EP 0w-20 with Valvoline Maxlife 10w-30 and confirming the performance characteristics, simply whether, when mixed with the six reference oils, whether the product separates or the pour point changes dramatically. That's it.

 

[radiometer]

I seems that some get away with mixing different oils for their cars. I don't know whether they keep those cars throughout the lifetime of the engine or not. Maybe some do. However, I won't mix oils for my cars. I just feel better about it this way.

 

[Blinker]

No they don't, please see my reply above. The miscibility standard appears to be widely mischaracterized.

ASTM D6922, from here: https://www.api.org/-/media/Files/C...hash=C16D3A3F94222F002EB3A1C9AC45BE19AC52ECA6
Denotes:
- Shall remain homogenous and, when mixed with ASTM reference oils, shall remain miscible:
View attachment 36145

That's all it promises.

The test:


They aren't mixing M1 EP 0w-20 with Valvoline Maxlife 10w-30 and confirming the performance characteristics, simply whether, when mixed with the six reference oils, whether the product separates or the pour point changes dramatically. That's it.

That quote you posted literally confirms what I said in that there is no harm in mixing.

 

[wemay]

Ignoring.

Telling response.

 

[Hogwash]

I just went out to the garage and found this. After several years of mixing oils for my mower without issue....the day of reckoning has arrived. It was a good machine. RIP

 

[Jimmy_Russells]

I just went out to the garage and found this. After several years of mixing oils for my mower without issue....the day of reckoning has arrived. It was a good machine. RIP

View attachment 36154

I see the problem, you added oil to an electric lawnmower

 

[wemay]

Mixing oils very rarely causes an issue. The only ref to issues I've read were presented by @Shannow. The circumstances surrounding the issue revolved around the mixed oils being used in extreme cold climate.

But what others have tried to convey is that once mixed, you have no idea what the final product meets with respect to certifications and approvals.

Now, the appearance that most SP/GF6 lubricants share additive technology may make mixing more desirable/palatable for many, but we should never consider the brew is better performing than the highest quality oil used in the mixture.

 

[Hogwash]

I see the problem, you added oil to an electric lawnmower

It worked great the 1st 5 years. Might explain the bubbling sound it always made.

 

[OVERKILL]

That quote you posted literally confirms what I said in that there is no harm in mixing.

Sounds like you need to re-read it.

 

[4WD]

Mixing oils very rarely causes an issue. The only ref to issues I've read were presented by @Shannow. The circumstances surrounding the issue revolved around the mixed oils being used in extreme cold climate.

But what others have tried to convey is that once mixed, you have no idea what the final product meets with respect to certifications and approvals.

Now, the appearance that most SP/GF6 lubricants share additive technology may make mixing more desirable/palatable for many, but we should never consider the brew is better performing than the highest quality oil used in the mixture.

Doubt it’s ever been properly tested … just isn’t done enough and why would an oil company or OEM endorse - much less pay for such a test.

 

[4WD]

I just went out to the garage and found this. After several years of mixing oils for my mower without issue....the day of reckoning has arrived. It was a good machine. RIP

View attachment 36154

looks like a peaceful protest

 

[OVERKILL]

Doubt it’s ever been properly tested … just isn’t done enough and why would an oil company or OEM endorse - much less pay for such a test.

Exactly. The test is just to confirm that, for the most part, an oil isn't going to, with a reasonable degree of certainty, split like mayonnaise or turn to gel at 0C in the event that you had to add a quart of something else, that was API approved, during an OCI. This is done by mixing the oil with 6 reference oils and watching for those issues. That's all the standard promises.

Some people seem to take that as an endorsement to toss together oils from different blenders and that they are guaranteed not to interact negatively, which clearly isn't the case. The test doesn't promise that any oil is universally compatible with any other oil, just that, when tested with the reference products, there were no negative interactions so the risk of dramatic negative synergies should be reasonably low.

 

[PimTac]

This thread has reached 50 posts and Jimmy with one L is laughing at everyone.

 

[4WD]

This thread has reached 50 posts and Jimmy with one L is laughing at everyone.

I’m laughing at myself because I’ll change my OPE oil 3x a year getting rid of misfit oil …

 

[SR5]

Right now in the beater I’m running a FrankenBrew of Penrite Vantage 10W40 semi-syn, Valvoline SynPower 0W40 full syn, Castrol Magnatec 10W30 semi-syn, Castrol Edge 10W30 full syn and Valvoline DuraBlend 10W40 semi-syn.

That should average out to an 8W36....perfect!

The other car is pure Castrol Edge 5W30 A3/B4

 

[Jimmy_Russells]

It worked great the 1st 5 years. Might explain the bubbling sound it always made.

 

[Blinker]

Exactly. The test is just to confirm that, for the most part, an oil isn't going to, with a reasonable degree of certainty, split like mayonnaise or turn to gel at 0C in the event that you had to add a quart of something else, that was API approved, during an OCI. This is done by mixing the oil with 6 reference oils and watching for those issues. That's all the standard promises.

Some people seem to take that as an endorsement to toss together oils from different blenders and that they are guaranteed not to interact negatively, which clearly isn't the case. The test doesn't promise that any oil is universally compatible with any other oil, just that, when tested with the reference products, there were no negative interactions so the risk of dramatic negative synergies should be reasonably low.

We don’t know what the reference oils are. If we do then I’ve never seen it. They could be specifically blended oils that are designed to cause negative effects when tested with sample oils with incompatible elements.

The OEM’s obviously care if motor oils are compatible with each other. I would imagine that warranty costs would skyrocket if oils weren’t compatible with each other and we would surely see disclaimers in owner’s manuals saying not to mix brands. What we have with the API is a collaborative effort between OEM’s, oil formulators, and oil marketers, and there is clearly a vested interest with all parties involved that all the products don’t cause undue harm to another competitors product.

If you are using the correct oil specification for your engine, using different brands simultaneously should be of no worry. If using a non API rated oil or OTC additives then all bets are off. After being here for 10 years I can’t believe how so many old myths still get circulated.

 

[OilReport99]

Can you mix 50/50 the leftovers for another fill, like Pennzoil 0w20 and Castrol Edge 5w40?

Yes, you can.

Both exceed the service grade for the vehicle.

But you don't know if the mix will unless you spend a few bucks to run all the required tests.

What exactly do you get with this mix

Just a mix, and a useless beat-to-death debate.

 

[farrarfan1]

This thread has reached 50 posts and Jimmy with one L is laughing at everyone.

I feel bad for Jimmy with two L’s, hopefully people don’t confuse him with the OP.

 

[OilReport99]

This thread has reached 50 posts and Jimmy with one L is laughing at everyone.

That's a matter of perception, trolls always are laughing at themselves. Precisely, they laugh at their inability to fit in.