Why the shift from 5w-40 to 0w-20

[MVW]

Why has the fourth generation of the E888 engine in my B9.5 Audi A4 switched from requiring 5W-40 oil in earlier iterations to 0W-20? Is this decision driven solely by the desire to reduce emissions and improve fuel consumption? While I understand that 0W-20 oil’s lower viscosity can enhance fuel economy, reduce emissions, and perform better in cold start conditions, I question whether this shift compromises the long-term health and durability of the engine. Notably, even other fourth-generation vehicles, such as the Audi S3 and Golf GTI, which I understand are tuned differently, recommend 0W-30 oil. The benefits of 0W-30, particularly in handling higher temperatures and stresses from spirited driving, are clear. So why does the Audi A4, with its more conservative tuning, use 0W-20 instead of 0W-30? Does this change in viscosity come at the expense of engine protection and longevity in favor of efficiency?


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[a4audi4fun]

Jury is out on longevity since many of those engines haven't aged enough yet but being able to pass tighter emissions testing regulations is the name of the game today for all car manufacturers.

[Nillious]

The real question hear is are there any real differences in the bearing clearance or oil pumps in the engines that are in the hybrid setup.

If the bearing clearance and pump are the same it probably has to do with operating temperature. If the hybrid setup doesn't heat the oil sufficiently they may call for the 20 grade in that case as it ends up running at the same viscosity as the 30 grade. The the golfs and gtis will obviously get the oil much hotter therefore calling for a higher viscosity.

[Hugh@EuropaParts]

From what I understand lower viscosity is used to get higher MPG on the spec sheet.

[shiro1745]

Has anyone tested the fuel consumption difference between the 0W-20 and 5W-40?
I just did my first oil change using 0W-20. I'm thinking to switch to 5W-40.

[MVW]

Has anyone tested the fuel consumption difference between the 0W-20 and 5W-40?
I just did my first oil change using 0W-20. I'm thinking to switch to 5W-40.

The fuel consumption differences between the two are likely negligible. I’m going to be switching to a 504 spec oil next week(5w-30). The 508 spec oil is very thin and I live in a warm climate so I see no benefit from a reliability standpoint.


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[Nillious]

In my eyes an engine is built to run 40w oil should not use a 20w oil. Audi likes to advertise good milage numbers and get you out of warranty. After that is not a concern to them.