Pep Boys warns Not to mix oils.

[veryHeavy]

I had 4 bottles of Pennzoil Yellow Bottle leftover from another car, but did not want to run straight conventional, so I decided to mix the stuff with synthetic:
- 2 of PYB 0W-20
- 2 of Mobil 1 5W-30

Based on the look on the Pep Boys manager, you'd think I asked him to pour acid in the engine.

"You can't be serious. You cannot mix different oils like that, especially synthetic and conventional." He wrote on my bill:

!!!CUSTOMER BROUGHT 4 DIFFERENT QUARTS OF OIL !!! ADVISED NOT A GOOD IDEA TO MIX OIL AND WEIGHTS !!!!

Car: Civic Hybrid 1.3 liter
Cost: $11 for the change & Proline filter

 

[crazyoildude]

And you let these idiots open your hood?

Anyway welcome to Bitog!
There are millions of vehicles on the road and millions of people dumping oil blindly into the crankcase and the engines still never skip a beat/..I wrote about someone i know who owns an auto repair shop and every oil change he does he puts the oil bottle upside down to drain every last bit and he uses that in his own vehicles with no problems. I usually try to stick with the same brand if i can until something makes me change..

 

[Danh]

Take a look at the Widman viscosity calculator: it advises not mixing oil of different brands. Oil manufacturers offer similar advice, suggesting that, while the the resulting viscosity is predictable, the effectiveness of the resulting add pack is not.

So, while your mix maybe OK, the Pep Boys advice isn't as outrageous as you think.

 

[53' Stude]

Crazyoildude is right; I wouldn't let PepGirls touch my wheelbarrow

 

[Skid]

I agree with the Pep Boys manager.

 

[NormanBuntz]

The Pep Boys manager could have been more tactful, but in his defense he's likely guarding against you coming back later and claiming Pep Boys approved the oils and that's why you had an oil related engine failure.

Practically speaking, chalk this up as another reason Pep Boys has sunk so low in the past 10-20 years. They used to be a favorite of mine.

 

[Garak]

Generally speaking, it's fine, but that depends what you define by fine. Synthetic and conventional (and all API oils) are to be miscible. But, that doesn't mean you're making a better blend than what you had before. In a warm climate, it's certainly not a big deal, but less than optimal.

In Minnesota, in a few weeks, you may very well be testing the cold cranking limits of the oil. There is no guarantee that your mix of 0w-20 and 5w-30 is a 0w-XX or 5w-XX at all. By the way, where are you getting 0w-20 PYB? I've never heard of such a product. Do you perhaps have a 5w-30 conventional and a 0w-20 synthetic? There are no "conventional" 0w-20 options, not that it matters much.

 

[JayhawkRoy]

Mobil says you are OK. From their FAQ:

Is it okay to mix conventional motor oil with Mobil 1 motor oil?
Yes. Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. But the superior performance of Mobil 1 will be reduced by diluting it.

 

[AirgunSavant]

Most makers containers note their oils are compatible with others and I would just
Try to stay and mix within the same brand although not gospel.

 

[veryHeavy]

OOOPS. I looked at my other PYB and you're right. It's 5W-20.

BTW the major problem with this Hybrid car is the 14-year-old battery. It has thrown "check battery" lights, so I expect it to die loooong before the engine ever does. Battery cost is $2500, so the car will be junked at that point.

 

[Skid]

Do you know to a certainty what type of base oils we are talking about? I'd never mix PAO and Group I-III, especially cold weather, due to the need for PPD for G I-III and no PPD in PAO. There's also a difference in what would be optimal for antioxidant (combination of amines/phenols versus amines only).

PYB is also high moly. High moly sometimes causes sediment issues with detergent. Most of these issues can be addressed with a short OCI. Which is why most people say to shorten the OCI when mixing.

 

[Ihatetochangeoil]

Amsoil says very similar things as M1:

Q: Can Amsoil motor oils be mixed with other brands?

A: Answer: Yes. AMSOIL synthetic motor oils are compatible with other conventional and synthetic motor oils. Mixing AMSOIL motor oils with other oils, however, will shorten the oil’s life expectancy and reduce the performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed. Mixing other oils with AMSOIL motor oils may also void the AMSOIL limited warranty.

https://www.amsoil.com/frequent.aspx

Soo...Whether anyone agrees that it is a good idea or not...My perspective as a BITOGER and an Amsoil user is: I always check my oil before long trips, and I carry a few quarts with me at all times. I have seen vehicles at various locations on Interstates that looked like they had someone's entire worldly possessions piled so high you couldn't see out the rear window...

I don't believe I've ever seen a car packed soo tightly that a quart or two of oil wouldn't fit in a corner of the trunk or under a seat somewhere...Other than purposefully using remnants from one's own stash, there is no spot in my brain for HAVING to mix oils (like out on the road somewhere).

Why, Santa, why? Oh, I forgot, there are people out there who have put ATF in the crankcase, sometimes even on purpose. I digress. You've done no harm...but I very rarely let someone else under my hood; that's a very private place.

 

[Garak]

Originally Posted By: Ihatetochangeoil
Amsoil says very similar things as M1:

I'd agree with all that, too, as another time to be cautious about mixing. Mobil and Amsoil won't back any mileage warranties when they're mixed with different tiers of their own line, much less mixed with competitors' products. So, it could be something to think about for someone pushing extended drains.

 

[CKN]

It would seem putting oil in of the exactly same spec is ideal. What's wrong with that?


Amsoil and Mobil says it's not the best situation. We need to find another thread or topic for a bash. Because the Manager wasn't "all wrong" on this one.

 

[69GTX]

I wouldn't have mixed M1 and PYB. 2 very different add packs. M1 is magnesium heavy and calcium light on the 20/30 grades. PYB is calcium heavy with no magnesium. So you get a mix of oil that has everything but sodium mixed in. You could have tossed in a quart of Valvoline to ensure you had at least 100 ppm Na as well.

I'd have no problem mixing PYB with PP, PU, PUP, QSUD, and Forumula Shell synthetic...all SOPUS products. I'd even toss in MSS and SuperTech synthetic since those are all high calcium oils too. But I prefer to keep the High Calcium, Magnesium and Sodium oils separated. There is no mfg I am aware of that mixes those together. So your PYB/M1 concoction is quite different from any oil on the market and therefore never tested.

 

[OneEyeJack]

With today's litigious culture I would agree with the manager 100%. Why risk a problem for a nickle/dime service. I would have looked into an exchange or some of the oil while also sticking with recommended viscosities and worked out some kind of deal and not mix oil. Members here do it all the time and I've never heard of a problem but since we don't know what's really in the bottle the safe bet is don't do it.

 

[barkingspider]

U never get 100% of the old oil out during oil changes so there is a small amount of oil mixing if u are using different oils at each oci. I have mixed oils w zero issues, but have never done it for more than 5-6K mile oci. I wouldn't worry about mixing oils too much.

 

[mclasser]

Originally Posted By: OneEyeJack
With today's litigious culture I would agree with the manager 100%. Why risk a problem for a nickle/dime service.

True. Gotta CYA.

 

[fdcg27]

That isn't really the issue nor is the difference in basestock blends.
The issue in blending dissimilar oils lies in potentially unfavorable VII interactions as well as the concern of whether the blended oils will meet the spec of either original.
The OP may no longer have a 5W qualified oil and his mix may not meet the intended API spec either.
To me, a mix of oils is just a way of using up leftover odds and ends for a summer run.
Heading into a MN winter, I'd have just bought a jug of either M1 or PP 0W-20 for ten or twelve bucks after the MIR that was available on both and run with that.
The OP lives in serious 0W qualification country so a 0W would be a good pick, not some blend with unknown CCV/MRV numbers.

 

[bunnspecial]

Because of additive pack differences, I try to stick to one brand/formulation in any given vehicle. I try to carry a quart or two all the time for that reason.

At the same time, if I'm at a gas station and need oil, I'll buy whatever they have in the right weight or the closest weight they have. I'd rather run with some oil of a different brand mixed in than to run low.

I also think of the person I helped at work the other day who had been advised to check her oil and thought she was doing something wrong when she pulled the stick out and there was nothing on it...I went digging and came up with a quart of Mobil 1 5W-20 and 2 quarts of PYB 20W-50. That's an odd concoction, but at the same time it got her back up to the full mark and her engine certainly sounded better.