The mixing of oils compared to increasing viscosity to combat oil dilution

[wemay]

If mixing oils (viscosity and different add packs) isn't optimum, why are we recommending going to increased viscosity to help combat oil dilution? Wouldn't the introduced fuel also alter the oil's make-up to the point we wouldn't know the final numbers (measurables)?

 

[SubieRubyRoo]

IMHO it's way overblown... we continue to see UOA after UOA on TGDIs like EcoBoosts and others that the wear numbers look fine even with elevated fuel. I wouldn't run the oil for extended OCIs but it appears nothing untoward is happening when changing the oil according to the OLM.

 

[parshisa]

I don't think that main idea behind increasing the viscosity it to combat oil dilution, It will dilute even if you put molasses. Slightly higher fresh oil viscosity supposedly will give you some better protection once the oil gets diluted. I guess that's the main idea behind it even though there really is no hard evidence that it does any better or worse. I personally am running 5w30 along with premium in my 1.5T 6MT. Fuel dilution doesn't seem to be a problem granted I live in Texas. I've done a couple of droplet test as I progressed in my OCI and they came back with minimal fuel ring. I should be changing oil again in about 10days or so and will have a sample collected for oil analyzers. Stay tuned and I'll provide another report on 5w30 before the new years (i assume to have around 7K on the fill).

 

[doyall]

Hopefully different add packs or different manufacturers/service specs are what primarily result in less than optimal results.

I fail to see how a 5W-20 brand X, spec Y mixed with a 5W-30 brand X, spec Y can be problematic (even as it relates to the 5W part). I can understand the uncertainties surrounding mixing a 0W and a 15W or mixing a brand X with a brand Z.

 

[Shannow]

Originally Posted by wemay
If mixing oils (viscosity and different add packs) isn't optimum, why are we recommending going to increased viscosity to help combat oil dilution? Wouldn't the introduced fuel also alter the oil's make-up to the point we wouldn't know the final numbers (measurables)?


Argument makes little sense.

It's still diluting the thinner oil too...

 

[wemay]

Originally Posted by Shannow
Originally Posted by wemay
If mixing oils (viscosity and different add packs) isn't optimum, why are we recommending going to increased viscosity to help combat oil dilution? Wouldn't the introduced fuel also alter the oil's make-up to the point we wouldn't know the final numbers (measurables)?


Argument makes little sense.

It's still diluting the thinner oil too...


It absolutely does make sense because that is my point as well. The fuel will still dilute and we don't know what other effects it may have on the oil. Just like "you don't know what you get as a final product when you mix oils" as is so often drilled on here when someone asks if they can mix, do you know what you're getting when oil is diluted by fuel? Does the ASTM test diluted motor oils?

It has nothing to do whether one oil is thick, thin or whatever.

 

[JAG]

Fuel affects the chemical reactions that occur in motor oil (almost all negatively) and obviously decreases the viscosity. It does both regardless of what oil it mixes with. If a person has engine that puts a lot of fuel in the oil, a thicker viscosity oil will compensate for that, by either undercompensating or overcompensating, depending on the amount of fuel and how much thicker the oil is that they change to. I don't understand what you are saying.

 

[Shannow]

Originally Posted by wemay
Originally Posted by Shannow
Originally Posted by wemay
If mixing oils (viscosity and different add packs) isn't optimum, why are we recommending going to increased viscosity to help combat oil dilution? Wouldn't the introduced fuel also alter the oil's make-up to the point we wouldn't know the final numbers (measurables)?


Argument makes little sense.

It's still diluting the thinner oil too...


It absolutely does make sense because that is my point as well. The fuel will still dilute and we don't know what other effects it may have on the oil. Just like "you don't know what you get as a final product when you mix oils" as is so often drilled on here when someone asks if they can mix, do you know what you're getting when oil is diluted by fuel? Does the ASTM test diluted motor oils?

It has nothing to do whether one oil is thick, thin or whatever.



But all things being equal...

for example, pick the same brand line...the effects will be similar in most respects....but the dilution will result in a higher number on the Stribeck curve.

Unless you are arguing a number of hypotheticals...
* that the thinner oil will end up thicker as a result of additive interaction with fuel dilution
* that the thicker oil will end up thinner than the above as a result of additive interaction with fuel dilution.

NOTE : there's NO API test for behaviours of oil with representative fuels, while there IS for behaviours with mixing oils.

I rest that the original argument makes little sense.


Two unknowns does not negate an understandable trend in direction.

 

[wemay]

That is what i was looking for. Much appreciated. The premise made little sense to you, and others in the know and i apologize for laymen presentation.

 

[4WD]

Reminds me of a case stuck in my mind that I never solved. About a year ago we were going to change the rear end gear oil on our 2013 Dodge Charger. That went well and then decided to only check the oil since it was just past 3k and we change that one at 5k due to lots of short trip driving. The oil on the dipstick looked like a burnt corn dog = very thick and black for the miles on an engine with only 48k on the clock.
The oil was 5w20 Castrol magnatec - we had some more so proceeded to change it. This was the strongest I had ever smelled gasoline - eye watering (car used E10 regular) - yet, again the oil was very thick.
I kind of wrote it off for "washing" effects and took it to the dealer to discuss. Diagnostics came back fine - no fuel or engine issues. We just started changing the oil at 4k going forward due to 90% "town" miles and how many months it took to even get that.

From Amsoil

Why is fuel dilution a problem?
•Reduced oil viscosity interferes with formation of a durable lubricating film, inviting wear. It also negatively affects the oil's ability to function as a hydraulic fluid, which is critical in engines with variable valve timing
•Fuel can wash oil from the cylinder wall, causing higher rates of ring, piston and cylinder wear
•Reduced effectiveness of detergency additives limits the oil's ability to guard against deposits
•Increased oil volatility results in higher oil consumption, requiring more frequent top-offs
•Accelerated oxidation reduces the oil's service life and requires more frequent oil changes

 

[ARB1977]

Originally Posted by parshisa
I don't think that main idea behind increasing the viscosity it to combat oil dilution, It will dilute even if you put molasses. Slightly higher fresh oil viscosity supposedly will give you some better protection once the oil gets diluted. I guess that's the main idea behind it even though there really is no hard evidence that it does any better or worse. I personally am running 5w30 along with premium in my 1.5T 6MT. Fuel dilution doesn't seem to be a problem granted I live in Texas. I've done a couple of droplet test as I progressed in my OCI and they came back with minimal fuel ring. I should be changing oil again in about 10days or so and will have a sample collected for oil analyzers. Stay tuned and I'll provide another report on 5w30 before the new years (i assume to have around 7K on the fill).

Our 1.8L Turbo uses 0W20 and mid grade gas. The oil smells like gas but no rise on the dipstick. I also live in Texas.

 

[FCD]

I've done it in my Escort, before i got the injection system properly tuned up it used to run rich and the oil smelled like fuel.
I ran ( and still am running ) 1L of 20W-50 mixed with 2.5L of 15W-40 HDEO.
My logic was and is it would help with the fuel dilution as the oil would start out as a thick 40 grade...

Now it runs perfect and the oil does not stink of fuel so at the enxt oil change soon i'll just put 15W-40 in it.