Trucks do well with lower cetane... within reason of course.
Remember running a 13-16 liter (even 18) 6 cylinder is different than much higher rpm 4 cylinder.... large ships diesel engines with cylinders you can physically stand in that are diesel and often run heavy bunker oil that's so thick it must be heated to be pumped...I don't even wanna know what that stuff would test at,
The difference isn't huge, but remember trucking is a game of pennies per mile and companies work hard to maximize mpg .... 2 tenths of a mpg is huge...some rigs even 10 years ago would occasionally get 10 mpg at 80,000 lbs. I've done it going across i-90 regularly hauling bottles Poland spring water and kegs of sam Adams beer. Sure....the HIGHER cetane fuel, either from the pump or thanks to an additive was better and easier driving but the the numbers didn't lie, even the "safety department" (catch all for most things) steered people get fuel at certain places... Irving in the NE typically has a interesting seasonal shift..so winter fuel there was generally avoided unless it was going to be extremely cold (they typically blend #1+#2 for winter rather than treating it)
Now was the better mpg cause there was slightly less power so people couldn't get their foot into it? Perhaps. Was it because the fuel was heavier so had more BTU? Very likely.
But the basics are...the typical VW TDI engine will always be running somewhat worse than ones in Europe running fuel that's tailored to them...there just isn't enough cars using diesel to refine "premium" diesel other than retailers dumping a bottle of additional additives in and saying premium.
Buy your fuel at reputable high volume sellers, keep your filter fresh and IMHO use a lubricity additive if you have a cp-4 pump. Beyond that drive more, worry less, enjoy your car.
