mixing 5w20 and 20w50

[rangerdood]

Buying what's left of the Havoline at Autozone. I have a '00 ranger that calls for 5w30, but I'd expect with over 80k on it to be able to run a 10w30 in the summer.

The only weights of Havoline left are 5w20 and 20w50. Can I mix these together to get something like a 12.5w35?

 

[mjoekingz28]

I just stuck 20w50 in my ride, but for you it still seems too cold to be considering it.

Anyway, I changed oil in an Expedition and used 4qts 10w30 and 2qts 20w50 giving 13w37 which I think is fine considering warmer weather is on its way.

But I don't understand Fords calling for 5w30 for everything. My manual uses weather to determine viscosity.

 

[Dyoel182]

Originally Posted By: mjoekingz28
But I don't understand Fords calling for 5w30 for everything. My manual uses weather to determine viscosity.


And 5w30 is an all weather oil just like 10w30.

 

[TallPaul]

You'll get something around a 10w40, perhaps a thin 10w40, if you mix them 50/50. If you have the 100C cSt viscosity numbers we can calculate it better. I don't see any problem running it in summer. If you want a 10w30, can bias towards more 5w20 in the mix.

 

[Audi Junkie]

Uh, they are two totally different oils. 20w-50 is good for some topping-off oil...maybe.

 

[mitchcoyote]

It's not good to mix oils of different weights....

 

[Triple_Se7en]

Originally Posted By: mitchcoyote
It's not good to mix oils of different weights....


There's no broadbased proof of that -- no broadbased proof that it helps or hurts. There's ebeen UOAs here that say otherwise. One of the best UOAs I ever read here involved a Mobil Drive Clean blend with Delvac. There's also been a sparkling UOA using Chevron's Delo 15W-40 with Havoline 5W-20..... plus others -- some even blending 2-3 different brands.

 

[glennc]

I agree. Lots of good UOAs with all sorts of mixes. Some exceptional.

Additive clash? I doubt it. Maybe additive non-optimization, to a tiny degree.

Also not a bad way to get the ideal seasonal blend for each oil change just by mixing different proportions.

 

[rangerdood]

My truck takes 5 quarts total, so I'm planning on 3 of 5w20, and 2 of 20w50. This should be just about right for this truck. Since they're the same brand, and same DepositShield line, I would imagine it should be fine to mix... It's not like they're going to stay separated in the crankcase.

 

[deven]

NO NO NO NO NO NO NO NO NO......Please NO

 

[glennc]

Originally Posted By: rangerdood
My truck takes 5 quarts total, so I'm planning on 3 of 5w20, and 2 of 20w50. This should be just about right for this truck. Since they're the same brand, and same DepositShield line, I would imagine it should be fine to mix... It's not like they're going to stay separated in the crankcase.
No, at worst there is the possibility that the two oils each have symbiotic chemical constituents by themselves but that when they're mixed, the delicate symbiotic balance will be upset and there will be some reduction not in the effectiveness of the individual additives, but in some of the additional benefit resulting from the particular balance of different compounds.

I don't doubt there is some of that, but the era of truly incompatible oil additives, and real additive clash, is over as far as I can tell. In reality it doesn't seem to matter what oils are mixed: the oil functions as oil with the resulting properties would be predicted to function, meaning that the viscosity result is calculable and the performance results are perfectly in line with what that would imply. In terms of UOA or any other type of evidence as to actual performance, I have not seen anything that indicates that this has not been the case, even one time.

 

[mitchcoyote]

You all are incorrect. A UOA is not the tell all end all of an oil. It would tell nothing good or bad concerning mixing of grades.

 

[rangerdood]

Originally Posted By: mitchcoyote
You all are incorrect. A UOA is not the tell all end all of an oil. It would tell nothing good or bad concerning mixing of grades.


Other than increased wear due to reduced effectiveness of the additive package. BUT, I have no prior UOA to base it on.

 

[hominid7]

Originally Posted By: mjoekingz28

But I don't understand Fords calling for 5w30 for everything. My manual uses weather to determine viscosity.


Ford back-spec'd most of their cars to use 5w30 for energy conserving reasons. They found through their EC test that not only did they achieve better MPG but that their 5w30 also protected very well.

The recently back-spec'd many cars to use 5w20 for the same reasons.

I dont think any engines seized or blew up as a result of being switched to 5w30 and i suspect the same will be true for 5w20. The exception may be that some cars were specificially not back-spec'd to use 5w20 but the dealer and repair network does not seem to do a very good job of determining which ones those were despite pretty clear TSB's.

It's my experience that Ford and Mazda dealers put 5w20 in everything unless they are specifically questioned about doing otherwise.

 

[glennc]

Originally Posted By: mitchcoyote
You all are incorrect. A UOA is not the tell all end all of an oil. It would tell nothing good or bad concerning mixing of grades.
If you're right about that I'd like to hear more. All the talk of mixing grades that I've followed here has not really indicated any reason that it might harm the oil's effectiveness, other than what I've already commented on. If you know something that hasn't been said I'd really be curious to hear it.

As for whether it would show up in UOA, I figure anything that affects wear should show up. If it actually protects less well, that should show up in wear. The only other "performance" function I can think of would be cleanliness, and I don't think anybody has suggested that cleanliness would suffer with a mix, and certainly haven't seen anybody try to post any reasoning or evidence for it.

Curious to hear more,

 

[dave1251]

By all means mix. Right now I am about to mix 5w-20 Pennzoil with 15W-40 Chevron DELO. In an 2-1 rato in a Ford 4.0.

 

[PT1]

As Jackie Gleason would say "NORTON...STAAAAAARRRRRT MIXING"

I have been mixing same brands different weights and different brands same weights for many years...never an issue.

 

[mitchcoyote]

Two different grades of oils don't magically mix into one new grade. You still have two grades in your engine. Some of the oil would flow at a faster rate than the rest of the oil. Least of the problems would be heat transference. Come on folks, ya'll really don't think you can blend oil better than a professional blender such as XOM. Your blends are not working at optimum performance.....

 

[VaderSS]

Originally Posted By: mitchcoyote
Two different grades of oils don't magically mix into one new grade.

Ummm..., It's not magic, but yes, they do make a new grade of oil. The problem is you can't know what that grade it is without extensive testing.

 

[rangerdood]

Originally Posted By: mitchcoyote
Two different grades of oils don't magically mix into one new grade. You still have two grades in your engine. Some of the oil would flow at a faster rate than the rest of the oil. Least of the problems would be heat transference. Come on folks, ya'll really don't think you can blend oil better than a professional blender such as XOM. Your blends are not working at optimum performance.....


So, products like the Lucas oil treatment, which we've found to simply be a viscosity modifier, don't actually mix in with the oil? It just sinks to the bottom?

I guess I should've figured on getting two wildly different answers when posting my question on an internet forum