Oil viscosity change question

[Alyusha]

I will be the first to admit, I know almost nothing about the differences of oil. I have always done my own oil changes, but always used the recommended oil. In this case, the recommended oil is 5W30 for my 99 Expedition 5.4L.

I have been doing some reading and understand the differences between the numbers and such. But I also see that many people start putting 10W30 when their engines get older.

I guess what I do not understand is why switch from 5W30 to 10W30 when the differences only have to do with starting the truck. If I wanted a thicker oil for my truck, should I switch to 10W40?

What I am thinking is to start using 10W30 (or 10W40) in the summer and switching back to a lower weight if need be in the winter. I am from Chicago.

Thanks for any info.

 

[Am3ricanInfid3L]

I'm no oil expert by any means, but I've always believed the difference between 5W30 and 10W30 was only during cold measures (not a huge difference, though). They both perform the same when the engine has reached normal operating temp, but 10W30 is (just a tiny bit) thicker, or slower during startup. Like 0.3 cst or something... I think faster (or thinner) oil during startup is a good thing, because it takes less force to push it through the engine. Less dry running during startup = less engine wear... I guess I just always believed the switch in oil was just a bunch of hocus pocus lol
But yes. If you want a thicker viscosity, 10W40 would be the way to go I believe.

 

[Alyusha]

I'm no oil expert by any means, but I've always believed the difference between 5W30 and 10W30 was only during cold measures (not a huge difference, though). They both perform the same when the engine has reached normal operating temp, but 10W30 is (just a tiny bit) thicker, or slower during startup. Like 0.3 cst or something... I think faster (or thinner) oil during startup is a good thing, because it takes less force to push it through the engine. Less dry running during startup = less engine wear... I guess I just always believed the switch in oil was just a bunch of hocus pocus lol

That's also what I established. One thing that made sense to me, was that due to wear, using a thicker (running) oil could help reduce engine noise or rough idle. But like you said, a thicker oil for start up wont matter 30 minutes into driving. Only the last number will.

 

[Am3ricanInfid3L]

Yep, pretty much. I totally read your question wrong at first by the way, sorry for any confusion.

5W30 performs the same as 10W30 during operating temp, but is slightly better during startup because it's just a wee bit thinner when cold. I've always seen it the same way as you, "5W" = cold viscosity. "30" = hot viscosity.

With that logic though, I'd aim for something like 0W40 for perfection lol

 

[Am3ricanInfid3L]

I went ahead and did some research on it, and found a great explanation. These guys break it down Barney style, and even provide charts for comparison.

Check em out -> Motor Oil Viscosity Grades Explained in Layman's Terms

 

[Alyusha]

Thanks for the info. It was very detailed.