Blending HDEO and PCMO

[nikorasu]

Last summer I took over changing the oil on my mothers Chrysler 300M with the 3.5 high output engine. This after finding my father had let the bulk oil and low end NAPA filter go 9,000 miles. I dumped that out and installed a Mobil 1 filter and a mix of Mobil Super Synthetic 10w30 and some old Valvoline 10w40 and 5w30 SJ oil that needed to be used. After 5,000 miles I drained that oil and refilled with more Super Synthetic 10w30, keeping the Mobil 1 filter in place.

At 136K that oil will be at 5,000 and the filter at 10,000 and it will get dumped. I want to switch her car over to using a mix of HDEO and PCMO and keep it with this for the rest of the life of the car.

When blending oil viscositys, I assume I can just average the two and get what the viscosity will be for the blend. IE three quarts of Mobil 1300 Super 15w40 blended with two quarts of Mobil Super Synthetic 5w20 would be 11w32, and 9w28 if I flip the number of quarts around?

I have a collection of Mobil Super Synthetic 5w20 at my parents house that I would like to use so the above seems reasonable to me. 11w32 for summer, 9w28 for winter. Really they are both close enough to 10w30 the numbers are the same for me but I would rather have more synthetic in the blend in the winter for cold start flow.

Thoughts?

 

[Artem]

I honestly don't see why not.

I personally don't like mixing and have never done so until recently when I bought a TON of oil during Kmart's clearance and now have a bunch of 10w40 that I need to use up so I started mixing a quart of 10w40 with four quarts of 5w30 in my 98 Camry.

Send a sample of the blend to the lab for analysis to confirm the viscosity. Perhaps you'll be able to extend the OCIs while you're at it as well.

 

[Gene K]

Repost

 

[m37charlie]

I don't know if you want to bother, but here is the viscosity calculator for mixtures:
http://www.widman.biz/English/Calculators/Mixtures.html

I don't think you'd do any harm over 1 OCI (make it not too long!) but I wouldn't make a habit of this unless you know the additive packs are very similar. Sometimes additives are synergistic and changing concentrations can have nonlinear results. An example would be certain boron compounds with ZDDP.

Charlie

 

[Gene K]

Your mix would be 10.82 cSt (Approximate). 30 Weight Range is 9.3-12.49 cSt.


Delvac has a conventional Moly/Boron Add Pack and MSS has a Sodium Add Pack. I would really prefer a sodium Add Pack Oil (Valvoline, Napa, Mobil non-HDEO and non-M1) for the blending agent. 2 Quarts of 10W40 would put you in the 10.2-10.5 range most likely.

If you really want a synthetic blend using HDEO (once you use up the MSS) why not just buy Rotella T5 10W30 for $16 a gallon from WalMart.

 

[nikorasu]

I in no way have to do what I suggested above. I just thought it would be a good way to use up some other oil but that was bought for the F150 but it can be saved for what it was intended for.

I was mainly after the higher detergent pack in the HDEO. I was not aware that there was a 10w30 HDEO available but I will try the T5 at the next change.

The 300M will get an OCI of 6,000 miles and T5 I guess for the foreseeable future.

Thanks all.

 

[Highline9]

I mix rotella T6 and PU5w20 in my challenger. My blackstone report came back excellent. Check the used oil analysis section.

 

[KCJeep]

I like to do it too, stay within manufacturer though IMO. The HDEO gives an anti-wear ZDDP boost while the PCMO will thin it down some, a good mix.

 

[dnewton3]

Originally Posted By: kb9skw
Thoughts?


This is going to be a bit harsh, but I think a does of reality is due. I believe you're not thinking about this clearly.

While I can agree that there is likely no harm to come from your witch's-brew escapade, I see no significant advantage to it either. Further, to the best of the information you've shared, you have no base-line UOA for comparisons nor other quantifiable parameters, to know whether the engine was harmed from the long initial OCI, or would be helped by the subsequent OCIs.

Until you define what your goal is, you really have no idea how to judge the success or failure of getting there.

As for the car itself, one extended OCI isn't going to condemn that motor to doom. Just because the "bulk oil and low end NAPA filter" went 9k miles, does not means things went terribly wrong. First, there is a buffer built into most OEM OCIs to begin with. Second, "bulk oil" certainly isn't premium stuff, but it's not automatically "junk" either. Most bulk lubes are perfectly fine for normal applications. Was the oil a bit "dirtier" from the longer OCI? Probably so. Did the oil shear down a bit, or thicken from oxidation? Possibly, but that doesn't means it was grossly out of grade.

You're being overly sensitive to the effects of one OCI, and now you're trying to over-compensate with a panic'd move to something "better" even though you've got no good idea where you currently stand, nor where you want to go, or how you're going to get there, or judge the progress you might make.

My apologies for the bluntness, but you asked for my "thoughts".

 

[Rob_Roy]

My "thoughts" are that you are really over thinking this. An oil of the proper spec and viscosity should be fine - change it every 5k if you want to be aggressive. If you want to run a HDEO in it, a CJ4 10w30 will work fine.

 

[benjy]

i see petroleum oils are "dated" for expiration, i read unless stored in a constant temp oil keeps changing viscosity in the container, not good, its said petroleum oils should not be used once they get old, if you mix stay with the same this i guess would include fake synthetics aka group III oils like castrol syntec etc, changing oil without the filter makes NO sense. mixing should be done within the same manufacturer also, IMHO

 

[Garak]

An oil's viscosity changes a lot more widely and a lot more often in the sump of an engine than it does in a sealed container in an uninsulated shed or even on the driveway.

 

[nikorasu]

Thanks dnewton3, I agree with everything you said. Sadly this is not the first time my dad has let the OCI go longer than it should... I once saw the milage on the windshield sticker and figured the car had gone 10K.

I just want to choose a single quality oil and stick with it. The car will get 6,000 changes as per the manual now and the T5 seems like a good choice for $4/quart.

Or I can stick with Mobil Super Synthetic at $3/quart.

 

[dubie2003]

T5 is my vote. Seems like that car will get the most benefit from it over the low-end syn from Mobil.

 

[dnewton3]

Originally Posted By: kb9skw
Thanks dnewton3, I agree with everything you said. Sadly this is not the first time my dad has let the OCI go longer than it should... I once saw the milage on the windshield sticker and figured the car had gone 10K.

I just want to choose a single quality oil and stick with it. The car will get 6,000 changes as per the manual now and the T5 seems like a good choice for $4/quart.

Or I can stick with Mobil Super Synthetic at $3/quart.


Both are overkill for 6k miles, but you migth as well run the lesser expensive of the two.