Why have EPA Ratings dropped on 2019 vs 2018 Suburban and some other non-GM vehicles despite no changes?

[K2xxSteve]

I noticed that the 2019 Suburban took a pretty significant 2 mpg overall drop in EPA fuel economy ratings, despite zero changes from 2018 to 2019. It seems to mainly affect the 5.3L, but the 6.2L took a small ding too. Some other manufacturers have been taking hits on 2019 vs 2018 fuel economy ratings on unchanged vehicles also, such as the Mercedes-Benz GLS450 4matic, and the Volvo XC90 T6 AWD. The Ford Expedition Max didn't drop from 2018 to 2019, however. 

 

Wonder what's going on? Methodology changes? I know that the EPA only tests/audits about 10% of the vehicles every year, and that they mostly depend on and accept manufacturer internal testing. Did GM get "audited" and hit with a bunch of hard testing by the EPA and that's caused the lower numbers? I also wonder if this has affected the 2019 Silverado launch and its "lower" fuel economy ratings versus the previous truck?  

TTAC has picked up on the same thing with the Chevy Colorado, and they don't know why either. 

https://www.thetruthaboutcars.com/2018/08/2019-chevrolet-colorado-diesel-takes-a-mysterious-fuel-economy-hit/

Whatever's happened is not specific to GM.

There also doesn't appear to be a global EPA methodology change affecting everybody.

Who knows? Any ideas?

[Ira1976]

I noticed that the 2019 Suburban took a pretty significant 2 mpg overall drop in EPA fuel economy ratings, despite zero changes from 2018 to 2019. It seems to mainly affect the 5.3L, but the 6.2L took a small ding too. Some other manufacturers have been taking hits on 2019 vs 2018 fuel economy ratings on unchanged vehicles also, such as the Mercedes-Benz GLS450 4matic, and the Volvo XC90 T6 AWD. The Ford Expedition Max didn't drop from 2018 to 2019, however. 
 
Wonder what's going on? Methodology changes? I know that the EPA only tests/audits about 10% of the vehicles every year, and that they mostly depend on and accept manufacturer internal testing. Did GM get "audited" and hit with a bunch of hard testing by the EPA and that's caused the lower numbers? I also wonder if this has affected the 2019 Silverado launch and its "lower" fuel economy ratings versus the previous truck?  

TTAC has picked up on the same thing with the Chevy Colorado, and they don't know why either. 

https://www.thetruthaboutcars.com/2018/08/2019-chevrolet-colorado-diesel-takes-a-mysterious-fuel-economy-hit/

Whatever's happened is not specific to GM.
There also doesn't appear to be a global EPA methodology change affecting everybody.

Who knows? Any ideas?

Well you see what happened with Volkswagen last year . Just like many companies that are trying to sell a product will exaggerate its capabilities for sales, until their card gets pulled . 26 mpg going downhill in neutral with the wind blowing behind you at 30 mph.

Sent from my SM-G955U using Tapatalk