Why do manufactures recommend/require the "w" and not leave it as optional?

[SC Maintenance]

They used to have motor oil charts with all the grades you could use.

I am pretty sure they have just chosen one mostly due to CAFE rules. Maybe also just to KISS. Most people think that 10W is higher viscosity than 5W so you would cause that debate.

 

[Patman]

They used to have motor oil charts with all the grades you could use.

I am pretty sure they have just chosen one mostly due to CAFE rules. Maybe also just to KISS. Most people think that 10W is higher viscosity than 5W so you would cause that debate.

There are still a lot of Corvette owners who refuse to use the recommended 0w-40 because they think it’s thinner than 5w-30
Many of them will say things like “I’m not putting that water thin 0 oil in my engine!”

 

[ATex7239]

A 0w-20 vs 5w-20 requirement is basically a way to require a fully synthetic oil made of Group III base stocks without actually putting it in print. 5W-20 oil can be made as a semi-synthetic. By requiring a synthetic oil, automakers can get away with a 10k oil change interval.

They make semi synthetic 0w-20 though.

 

[Klutch9]

You're giving way too much credit that average users understand or care what the "w" is about. Heck we have plenty here who aren't clear on it.

I thought the ‘W’ stood for wumbo?

 

[D1dad]

My 03 Altima 2.5 listed 5w30 up to 10w40. Now 23 years later it’s simply 0w20 for the 2.5. Yes the engine has changed, but how much? I use 0w20 or 5w20 simply because it works and has given me no reason not to. If I ever start consuming oil I’d go 0 or 5w30. So far so good.

 

[kschachn]

Because CAFE requirements and the wide range of temperature variations in the North America I imagine. CAFE doesn’t really let manufacturers let us choose. But that’s just my guess.

The actual answer here in response #1.

 

[crashz]

Two single men from a motor oil forum isn't exactly a wide sampling of the population.

The only sorting I do is greasy clothes/regular clothes/dry cleaning. And I am married, but we separate laundry duties. I can't be responsible for messing up my wife's duds.

That's not to say I dress like a slob. On the other hand I was not selected as a character in the new Devil Wears Prada movie.

 

[IndyIan]

Same here.

I do too, but I try not to have white clothes in general... A new red shirt makes the all in one load laundry method not very effective if you like having whites. I still wear my pink t-shirt though.

 

[Prison_Mike]

When most of the people just mix their white and colorful clothes and wash them all at once with the same detergent at the same temp.

I've done this for years. Only exception has been new jeans the first couple times, and even then I'll wash those with anything darker than them. Never once had an issue in over 20 years. Wash everything on cold except a couple things. Saves money and detergents are meant to work in all temps anyway.

 

[Tom NJ]

Always lots of questions about the specifications by manufacturers.

Why do they see the need to stress one "w" over another? 0w or 5w for example

Could/should they just use "x" and leave it up to the users to decide based on location? Xw-16?

So many folks get hung up on the manufacturers recommendation and worry about warranty...which I understand.

Conceptual question about "why" stress a certain "w"...not about the virtues of the "w"

As I understand it, manufacturers use 0W-20 oil in their fuel economy testing to get maximum CAFE benefit, and therefore must also recommend/require this grade in their owner's manual. Exceptions may be allowed for specific driving or environmental conditions, or for top-off with a return to the recommended grade in the next oil change.

 

[OM617YOTA]

Some of it's also for product consolidation. With modern oils and sane OCIs there's just no reason to run 5w or 10w anymore, a 0w-whatever will be perfectly fine from the Bahamas to Canada. No reason to stock a 0w30, 5w30, and 10w30, when a 0w30 will cover all of it.

Yes there are tradeoffs and I'm even aware of some of them. Nobody outside BITOG knows or cares about those tradeoffs, and more importantly, they mostly don't need to know or care either.

 

[OVERKILL]

As I understand it, manufacturers use 0W-20 oil in their fuel economy testing to get maximum CAFE benefit, and therefore must also recommend/require this grade in their owner's manual. Exceptions may be allowed for specific driving or environmental conditions, or for top-off with a return to the recommended grade in the next oil change.

Exactly this. The grade used to qualify for CAFE is the grade required to be indicated by the manufacturer. Since OEM's are penalized for poor fuel economy, there is a strong incentive to pursue incremental gains through simple measures like the grade of oil being used, which is how we ended up on this trend of thinner and thinner oils.

The availability of inexpensive bases like Mobil's EHC slate has also meant that the bar to get the 0W-xx Winter grade has been lowered, which motivated OEM's like FCA/Stellantis for example, to shift their recommendation from 5W-20 to 0W-20, since the cost of procurement became effectively identical (which had historically not been the case).

 

[SC Maintenance]

I do too, but I try not to have white clothes in general... A new red shirt makes the all in one load laundry method not very effective if you like having whites. I still wear my pink t-shirt though.

First wash on its own warm. After that together with tap cold, which in summer here is still warm

I haven't had anything run colors in years. Pink tidies is a thing of the past.

 

[edyvw]

There are still a lot of Corvette owners who refuse to use the recommended 0w-40 because they think it’s thinner than 5w-30
Many of them will say things like “I’m not putting that water thin 0 oil in my engine!”

Man, if i could have a penny every time someone says 5W30 is thicker than 0W40 in BMW forums or Facebook pages.

 

[ka9mnx]

I don't see much future for 5w-xx oil.

 

[The Critic]

I don't see much future for 5w-xx oil.

Ford doesn't seem to be moving away from 5W-30 for their 3.5 Ecoboom.

 

[ripcord]

They make semi synthetic 0w-20 though.

Semi synthetic 0w-20 is still pretty uncommon and I would wager has little to no Group II base stocks in it.

 

[Japanese]

I don't see much future for 5w-xx oil.

There is bright future for 5W-XX as all-year-round oil. The least all 0W-20 owners go to such oil sooner or later. Last but not least - it's widely used in the army, even as conventional.

 

[ka9mnx]

There is bright future for 5W-XX as all-year-round oil. The least all 0W-20 owners go to such oil sooner or later. Last but not least - it's widely used in the army, even as conventional.

Yea, but that's the ARMY...

Trust me. 0w-xx WILL replace 5w. It's already happening.

 

[SC Maintenance]

There is bright future for 5W-XX as all-year-round oil. The least all 0W-20 owners go to such oil sooner or later. Last but not least - it's widely used in the army, even as conventional.

Correct me if I am wrong, but 5W is spec'd to -22F. Thats pretty cold, but there are plenty of places in USA that get colder occasionally.

0W is spec'd -40F. Not many get that cold, but if you want to test with one oil and put one oil in the manual?

10W-30 was common at one point also - but as more and more cars started specing 5W it eventually become fairly uncommon.