I document all of my fuel use so I know from tank to tank exactly what my vehicles burn. I also haul the same weights on the same runs. When I get fuel that comes from refinerys Saskatchewan the trucks always go further between fill ups. If you do a little research you will find out that the tar sand diesel fuel does not have as much energy in it that crude oil diesel has. If you talk to truckers that travel a lot they will tell you the same thing. Some farmers that I know who burn a lot of fuel get their fuel trucked in from Saskatchewan because it is better fuel.
The old high sulfer diesel fuel gave me the best fuel economy in all of my diesel units. When I was in the states traveling a few years ago I got the odd tank of this and we got better than 40% more mileage per tank. Even without the sulpher you can tell good fuel from poor fuel.
Most people do not document their fuel use and quote the "lie meter" on many forums. You have to start a fuel log book to know exactly what is going on. Then after many tanks of fuel you can actually see any changes in fuel economy.
While reading this thread I was thinking this the whole time
I happen to know a lot of truck drivers and they swear when in southern sask you have to fill up at a co-op they say it is denser and your MPG goes way up. They say the Co-op refinery in Regina produces a better diesel than Alberta refineries ...maybe it has something to do with the Sask mandatory 2% bio-diesel?