5w vs 10w

[dlundblad]

Can somebody school me on the differences? 5w for anything below 0 degrees F obviously but what's the difference besides that? Would wear be any different if both were ran in 75 degree F weather? I read a few places where the 10w allows the oil to adhere to parts for the next start up.. How much of a fact is that?

Thanks.

 

[HangFire]

Are you asking about straight-weight SAE 5W and 10W "Winter" oil, or the lower end of multi-viscosity oil, such as 10w30?

 

[bepperb]

As a massive over generalization that people can (and probably will) poke holes in the lower VI oils with a narrower spread (like a 10w30 or a sae 30) will cost less to produce and likely be more shear resistant.

The higher VI oils will improve fuel economy when the oil is not at full temperature (which can be the majority of the time when a car is only used on short trips) and actually for the current SN grade they are required to meet a slightly higher fuel economy target.

Wear is subject to debate, in theory the higher VI oil would cut down on startup wear, then again if it was too thin (from shear or otherwise) to give full protection under a high temperature high load condition then wear would increase.

 

[dlundblad]

Probably should have specified. Lol. But yes multigrade. Let's just say 5w30 and 10w30 for conversation sake.

 

[bepperb]

Well let's lay out some assumptions... that it's Pennzoil conventional we're talking about, that both weights are using the same base stock that is group 2 (conventional) with a viscosity index of 120.

And so let's pretend they used that base stock to make a SAE 30 with the VI of 120 and no index improvers.

And then to make the 10w30 with a VI of 138 they have to add some VI improvers.... and to make the 5w30 with a VI of 158 even more. Well historically viscosity index improvers are expensive and prone to shear.

So you have three oils made with differing levels of an additive that has a huge positive (better cold performance) but a couple negatives. And you could pick which suits the situation best and go from there.

That probably would have been the case 30 years ago. Now there are cheap group 3 base oils with a much higher than 120 viscosity index, and it's possible to make a 10w30 with no VI improvers at all fairly cheaply. And there are group 4 and 5 base oils with high enough VI's to make 5w30 and 0w30 oils with no improvers... so there really isn't a negative to using the higher VI finished product with the exception of cost.

I worry this adds to the confustion more than it helps, but maybe you get something from this (I hope).

 

[Shannow]

Originally Posted By: dlundblad
Would wear be any different if both were ran in 75 degree F weather?


At 75F...absolutely no difference in wear assuming that both oils had the same anti-wear add packs.

Unless using oil grossly unsuited to ambient temperature, and then the time taken for the lubricant to fill galleries and reach remote parts will have an impact, and probably serious...(see Esso vids on HDMOs at very low temperatures)


Originally Posted By: dlundblad
I read a few places where the 10w allows the oil to adhere to parts for the next start up.. How much of a fact is that?

Thanks.


None really, I've seen it pop up here on BITOG from time to time, but it's not right.

Every wetted engine part will have oil on it next time you start it...the W rating won't make it any more. Lower VI might make it operationally thicker, and be more resistant to squeeze film loss, but at cold start, the remnant oil will be many many times thicker than at temperature, so probably no difference there really.

 

[Hyde244]

In general, 5w30 will be the only oil you'll ever need.

 

[toneydoc]

I have the same engine in my Jeep. I am in a warmer state than you and mine gets either 5w or 10w depending on what I have on hand at oil change time. Now if I was in Indiana, I would use 0w for winter time use as you do get some cold weather. Reason being is the 0w will flow better on those mornings when you do get really cold. Other than that, they will probably be equal in other properties in that engine. It is a good engine if properly maintained with good products.

 

[gfh77665]

Originally Posted By: Hyde244
In general, 5w30 will be the only oil you'll ever need.


He is on the right track, but there is more. In Ohio and places like that, 5-30 is generally all that would ever be needed.

Across the sunbelt, 10-30 is generally all you would ever need.

Realistically, these two oils are almost identical.

 

[HTSS_TR]

Conventional 5W30 of SG-SH was not as shear stable as 10W30, 5W30 of newer API SM-SN is very shear stable almost as good as 10W30. Synthetic 5W30 is so shear stable such that 10W30 is very much obsolete. Almost no manufacture is recommending synthetic 10W30 for their engines in the last 3-4 years.