much difference in 5w/20 & 5w/30 motor oil?

[wit-nit]

With 179,000 miles on the engine I would probably now go with the heavier 30w because of the wear and tear on the moving parts that are loosening up inside the engine.

[thejackalope]

Originally Posted by southernnaturelover

In a hot climate I don't see how 5w-20 would be better than 5w-30. The winter viscosity (5w) of both should be the same.

In theory the smaller the difference in numbers the better because it means less polymer additives are used to adjust the viscosity

As I understand, conventional 5W-30 oil is 5 weight with stuff added to make it 30 weight at high temperature. Then those additives wear out and viscosity goes down with use and I guess lubrication also isn't as effective. The 5W-20 would have less additives. But it would still always be less viscous than 5W-30 right?

Synthetic apparently starts out as 30 weight or 20 weight and has additives to make it thinner at lower temperature so it's the opposite.

Last time I was choosing oil I was deciding between 5W-30 and 10W-30 from Pennzoil... Most "oil enthusiasts" on forums like BITOG say to use the 5W-30 because it has no disadvantage. Except I looked up the specs and the 10 had almost half the NOACK volatility, I assume due to fewer additives, so that's what I got. When you have a turbo that kind of thing makes a difference

[SoCalCpl2]

The low number (5) represents the viscosity for winter driving... The high number (20/30) is for warmer driving (or when your engine warms up) and either one is fine to use all the time....

[Eightball35]

I have a 07 ram I put half 5w20 and half5w30 cause I had some left over do you think there will be a problem. I used Castrol full synthetic motor oil.

[Larry Caldwell]

Originally Posted by hoffdano

I assume you meant 5 qts. 5W30 is a heavier weight oil than 5W20. You might lose a slight bit of fuel economy, though you won't harm your engine. For one oil change there is no harm done. In general though I like to use the oil viscosity the carmaker says to use.

I remember reading that the engine in my pickup would run fine on either 5w-20 or 5w-30, but there was a particular engine that could be damaged by 5w-30 because it used oil flow to cool internal parts of the engine. My engine is the Ford/Mazda 3.0L 6. I don't remember which one required the 5w-20.

[Larry Caldwell]

Originally Posted by Eightball35

I have a 07 ram I put half 5w20 and half5w30 cause I had some left over do you think there will be a problem. I used Castrol full synthetic motor oil.

It's better than no oil. You should probably ask Castrol if different weights are compatible.