Curious response from Mobil 1 on mixing viscosities

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Getting ready for an oil change this weekend. I need 6 qts of oil and have two 5 qt jugs of Mobil 1. One his a high mileage 5W-30, the other a 0W-30 AFE. I reached out to Mobil and asked about mixing 5 qts of the AFE with one quart of the high mileage. Here is their response:

"Thanks for writing to us. All of our oils are formulated to be chemically safe in combination with each other. We do not, however, recommend mixing SAE grades. The SAE viscosity numbers measure physical flow rate characteristics, rather than chemistry."


Besides thickening up (a bit) the 0W-30, what's the downside? Any guesses on what's behind their take on mixing the two viscosities?
 
I am sure their response is a safe one so you do not mix something that does not meet the viscosity required by any warranty. They are just covering themselves.
 
That's standard response. They can't say for sure the resulting mix wouldn't end up 0W-30 instead of the 5W-30 called for. Also if you were to have a warranty claim denied based on the wrong oil.they don't want to be culpable. The same reason they warranty M1 AP for 20,000 mi but then have a follow your OLM or Manufacturers Recommendation disclaimer.
 
Such a little amount will make 0 difference. They need to protect themselves at all costs from any possible liability.
 
It won't matter at all. I've added quarts of Trop Artic to QSUD in the past with no effect.

You can mix oils together. Is it optimum? Probably not, but the engine doesn't know the difference. As long as there is a film of decent oil between the moving parts it's all the same to the metal inside the engine.
 
I mix Mobil AFE 0w20 and multiple flavors of 5w30 all the time. Usually do a half and half. Never worried a bit about it. The 1.5L in my Honda is known for dilution (in the CR-V at least) so I feel warm and fuzzy inside making a 2.5w25 just as a little reassurance it doesn't thin out too much. Probably unnecessary but I don't care. Engine will never know the difference.
 
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The final viscosity at high temperature will still be a 30-weight.
What is less (or not) predictable is the low temperature viscosity of 5W or 0W.
Mixing one quart out of six doesn't seem like enough to degrade cold flow to take a 0W to a 5W. But the resulting oil should still be at least a 5W.
 
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There is always mixing as there is a gob of residual oil in the engine even if you drain all day. Of course you could follow the oil change procedure of that YouTube rockstar with the Smart car and squeeze a good bit more out of the system.
 
What they are saying is that some oils have a different chemistry from others. For example, their 0W-40 has (I think) more MoS2 in it that other grades don't have. High-mileage oils have their own unique chemistries.

What does this mean in practical terms?.... not much. But then we're an oil web site; such esoterica are discussed.
 
I have a Hyundai that I have mixed different amounts of 5 different oils into:

Master Pro Tech 5w30 synthetic
Carquest 5w30 synthetic
Resolute 10w30 conventional
Mobil 1 0w40
Valvoline 5w40 MST

Car has never run better
grin2.gif
 
Originally Posted by A_Harman
The final viscosity at high temperature will still be a 30-weight.
What is less (or not) predictable is the low temperature viscosity of 5W or 0W.
Mixing one quart out of six doesn't seem like enough to degrade cold flow to take a 0W to a 5W. But the resulting oil should still be at least a 5W.


This is probably so … personally I mix same brand and grade - like M1 AFE with M1 EP when I have a couple quarts left in a jug … again, in same grade.
 
The overall viscosity of your oil changes after driving just 1,000 miles due to shear, volatility/burnoff, fuel dilution, oxidation, suspension of particulates, etc. Probably not significantly, depends on the engine and usage. But the slight change in viscosity due to mixing these two oils is not going to cause an issue.

Put in 5 quarts of the AFE 0w30 and check the oil level. You might find that it's in the safe zone and you don't need to mix at all.

My question: why did you buy two different viscosities and flavors in the first place? High mileage and AFE? If you had a purpose for buying these specific products, you might be defeating that purpose by mixing tem.
 
A while back I mixed like a dozen random oils of different brands, viscosity, etc into a big bucket. I've slowly been using that up in friends cars to top up or occasionally change oil. 0 issues. All these are older cars so nothing under warranty.
 
Originally Posted by DGXR
The overall viscosity of your oil changes after driving just 1,000

Put in 5 quarts of the AFE 0w30 and check the oil level. You might find that it's in the safe zone and you don't need to mix at all.


Agreed, most of my cars can be filled a full quart low and still show "safe"

But if he burns any or even if not I find the car will degrade the oil faster if your a tad under the fill QTY. (aka the car gets noisier faster and the oil blackens quicker)

Also will have to check oil levels often and have some top off oil in tow just in case.
 
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Next OCI on the Wrangler I'm going to get six single quarts of different oils and mix them all together just to see what happens.
 
Originally Posted by Jimmy_Russells
Next OCI on the Wrangler I'm going to get six single quarts of different oils and mix them all together just to see what happens.

What do you expect to happen? My guess is nothing.
 
I've used mixes of tons of oil in the past. As mentioned, that remaining .5-2qts left over goes in a bucket.
My ladies Fiesta will be getting 2 qts schaeffers, 1qt formula shell conventional, .5qts of valvoline synpower, .5 qts of peak synthetic all 5w20, with the remaining .2 qt Dollar General ND 30 sometime in December.

12 years ago I used the remaining different oils I had left over from various applications in my old Ranger. The oil from what I remember consisted of
.5 qt 0w20 Amsoil XL
.5 qt 20w50 VR1
.5 qt 10w30 QSHM W/50
.5 qt 5w20 Peak Conventional
1 qt 10w30 RPMaximum
1 qt SAE 30 Briggs
And .5 qt ND 30 Dollar General.
Plus a yellow pure one, that oil was ran for 5K, no burn off, drained
Then dumped into my dads oil burning saturn for 3k, It burned 1qt or so, then the remnants of that ran in the lawn tractor (along with the PL20195 filter from the truck) for a summer with no burn off.

Did it harm anything? Idk, the truck and car still run, technically the tractor engine still runs although the body succumbed to rust so
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If I wasnt a dumb poor 16 year old and knew at the time, I shoulda done a VOA/UOA just for giggles.

If you're out of warranty go ahead. In warranty I wouldnt.
 
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Originally Posted by rubberchicken
I personally would feel safe mixing the two.


I would also, and have mixed and will mix in the future.

IMO Mobil's response is due to 2 things:

1). Unpredictability of actual viscosity (in some conditions)

and

2). Lawyers.
 
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