My old B5.9 coupled with my fairly light coach ( no slides ) can get about 11.5 MPG. I have read threads where the newer motors get about 10-15 % less than that. I can imagine that additions of emission control equipment can make the engine burn cleaner but not more efficient. I may be thinking incorrectly but does the emission equipment out weigh the old mechanical technology if it burns more cleanly yet takes more fuel to go the same distance. To do so these new motors would have to be much more emissions friendly than the 10 - 15 % that is lost in economy. I am not saying I know this answer just inquiring from those that have better information. I know gas motors have come a long way from the old carburetor days and emissions as well as mileage is now much better so what about diesel.

Generally, todays engines get much better mileage and with less pollution than the older ones.....I am not sure what a B5.9 is, can you be more specific? (make, year)How heavy is your rig, how big?I haul a 5000 lb 5th wheel with my 97 GMC 5.7 (350 cu in) and get about 10 mpg

Poncho, he is likely talking about his Cummins 5.9l.

There is no doubt that the diesel engines are running cleaner now, because of low sulfur fuel and because of the DEF to reduce emissions. In fact, according to the EPA, the lower sulfur diesel fuel has been so successful that, starting in 2017, the EPA is setting standards to reduce the sulfur content in gasoline. Of course the cost of gasoline will increase, just as the price of diesel increased, as the refinement costs increases. I do not remember reading that the truck drivers are complaining about getting less mileage from the newer fuels or from the DEF. It is a fact that the ethanol fuels produce lower fuel mileage with the gasoline powered vehicles. It is just a guess as to what will happen to fuel mileage in gasoline powered vehicles with ethanol and the lower sulfur fuels after 2017. 2017 EPA requirements

One can only hope that the government acquires some degree of common sense between now and then and rethinks the whole fuel situation. Ethanol has been a disaster in that it doesn't achieve any of it's intended goals.Jim

new engines emit less per mile than yours because the emission controls reduce the emissions You engine has no emission controls that I know of. Do you know what emission controls your engine may have?Most DEF folks are achieving much better mileage than none DEF folks and their previous vehicle. Based on what little I know DEF has been a success and more than makes up for the mileage drop from the low sulphur fuel,

Fuel mileage vs pollution | Good Sam Community

tomman58
Explorer
Jun 09, 2014
I you are happy with your 93' RV then why worry. sounds like you are not into having the current trend anyways as most of us really like slide outs and the features of the newer lighter units. I think the new truck 2015 dmax will get better mileage then my last and my last didn't do bad art all.
wallynm
Explorer
Jun 09, 2014
And a cash machine for certain large corporation.

Lobstah wrote:
O. Ethanol has been a disaster in that it doesn't achieve any of it's intended goals.

Jim
wallynm
Explorer
Jun 09, 2014
new engines emit less per mile than yours because the emission controls reduce the emissions You engine has no emission controls that I know of. Do you know what emission controls your engine may have?

Most DEF folks are achieving much better mileage than none DEF folks and their previous vehicle. Based on what little I know DEF has been a success and more than makes up for the mileage drop from the low sulphur fuel,
Lobstah
Explorer
Jun 09, 2014
One can only hope that the government acquires some degree of common sense between now and then and rethinks the whole fuel situation. Ethanol has been a disaster in that it doesn't achieve any of it's intended goals.

Jim
rgatijnet1
Explorer III
Jun 09, 2014
There is no doubt that the diesel engines are running cleaner now, because of low sulfur fuel and because of the DEF to reduce emissions. In fact, according to the EPA, the lower sulfur diesel fuel has been so successful that, starting in 2017, the EPA is setting standards to reduce the sulfur content in gasoline. Of course the cost of gasoline will increase, just as the price of diesel increased, as the refinement costs increases.
I do not remember reading that the truck drivers are complaining about getting less mileage from the newer fuels or from the DEF.
It is a fact that the ethanol fuels produce lower fuel mileage with the gasoline powered vehicles. It is just a guess as to what will happen to fuel mileage in gasoline powered vehicles with ethanol and the lower sulfur fuels after 2017. 2017 EPA requirements
ChooChooMan74
Explorer
Jun 09, 2014
Poncho, he is likely talking about his Cummins 5.9l.
poncho62
Explorer
Jun 09, 2014
Generally, todays engines get much better mileage and with less pollution than the older ones.....I am not sure what a B5.9 is, can you be more specific? (make, year)
How heavy is your rig, how big?
I haul a 5000 lb 5th wheel with my 97 GMC 5.7 (350 cu in) and get about 10 mpg

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