Help. I accidentally put 1 quart of Mobil 1 0w40 in with my 6 quarts of 5w20. Should I be concerned? Thanks. That's what I get for not paying attention.
( 2010 F150 V8)

 

No dont sweat it all will be fine.

 

Nope. You just have a slightly thicker oil as a result. One quart in six isn't enough to make any kind of worthwhile difference anyway.

Drive your truck, it'll be just fine.

 

I'd say you ended up with 4w23 oil.

i wouldn't sweat it.

 

Just keep an eye and ear out to notice if anything changes. I wouldn't run an extended oil change on this . This does not make a thicker oil as it will be 2 different oils circulating together.

 

That's not true, they mix together and form a thicker oil. There's nothing wrong with extended drain intervals with this either.

 

That's right...they blend together to make a slightly thicker oil. They won't stay seperate and it won't cause any trouble.

 

Run it for your normal interval and have no worries.

 

I do not see how two different engineered viscosity oils will mix as this is at the molecular level not fluid . As the heat increases the individual molecule oils will attain their own viscosity. There was always a warning from experts that mixing same viscosity oils was ok ,but not different viscosities.

 

so he will have 14% of his oil reaching a different viscosity at a different rate than the other 86%.

the 14% will be homogenously distributed amongst the other 86%.

whether they mix at a molecular level or not, they are mixed at a fluid level and will act as a homogenous fluid.

do you suppose that all 6 quarts of 5w20 were EXACTLY 5w20? i would be they aren't.

 

Other than the normal awareness for unusual noises I would not even think twice about it. Might not add the 0w40 intentionally but having done so I highly doubt it will make any issues, especially a nice synthetic like M1 and especially in a high VII multi weight like 0w40 (0 base weight with VII to bring it up to a 40 weight at operating temp).

 

You can make your own custom viscosity by mixing the proper amounts of two differnt viscosity oils. This is rarely necessary due to the wide range of oil available.

The viscosity of a given oil is changed with polymeric additives. These are long chain molecules that help to increase the viscosity of a base oil. The problem they present is that they can be broken down under high shear conditions.


I'll also note that I am not an expert in tribology. But if you want to get a great book I recommend:
Engineering Tribology 4th Edition
ISBN: 978-0-12-397047-3

I'm only part way through that book. It was purchased because the compnany I work for has a turbine needing an oil change due to a high total acid number (TAN). We have been unable to treat the oil to reduce it and now I understand why. The cost of the oil change is somehwere around $40K so the cost of the book was negligible.