Fuel mileage diesel vs gas

I have the 6.7 Powerstroke and love it. Just drove from Richmond VA to Winchester VA about 150 miles and the dash said 12.8. It was stop and go for a while and it knocked it down from 13.3 at the high. No towing and I was doing 55 mph most of the way.

John S. - what engine do you have in the F550?

Ok, I owned a 24 foot born free with the e450 with v10. I would get 8-9 mpg. I just bought a 29 foot born free on a f550. It gets 12-12.5 in the mountains and around town on the flats and at 65 mpg I get 13 mpg.

I have a Navion 24G on the Sprinter chassis. I have to add a 2.5 gallon jug of DEF roughly every 5k miles. It costs about $12 at Walmart. One nice thing about the extra mpg is the longer distance you can go between fuel stops. My old rig, 1997 F250 with the 7.5l V8 and a Lance camper got about 8 mpg and held about 35 gallons of gas so I was looking for fuel starting at about 200 miles from full. The Navion holds 26 gallons of diesel and gets 15 mpg so I can comfortably go about 300 miles before I start looking ( I don't like to get much below 1/4 tank). And at 14k miles per year I do believe the extra cost of the diesel is worth it, not that I have to justify it to anyone but myself.

In my experience, that information is in error (a diesel only beating a gasoline engine by 1 or 2 mpg). A diesel pulling a heavy load will beat a gasoline engine by approximately 40 to 50 percent in fuel mileage, so a gasoline engine pulling a given load engine getting 10 mpg, will be beaten by a diesel pulling the same load getting approximately 14 to 15 mpg. Of course, the picture is complicated somewhat by the factor of fuel cost. Where I am, diesel fuel presently costs five percent more than gasoline. If you factor that in, the operational fuel cost advantage of diesel drops to approximately 40 percent, which is still substantially better than "1 or 2 miles per gallon." However, in some localities, the price differential may be slightly less or slightly more. The national average U.S. fuel prices as of 17 July 2017, showed that the average price difference of diesel fuel over gasoline was 4.14 percent.
Of course, the above discussion does not take into consideration that a diesel engine option typically costs thousands of dollars more than the standard gasoline engine that it is replacing. And the maintenance costs for a diesel engine are significantly higher. So unless you drive a lot of miles annually (in my opinion at least 15,000 miles or more annually), it's hard to justify a diesel engine on the purchase of a new vehicle. A few years ago I was about to purchase a new pickup, and considered getting a diesel. I ran the numbers on it and it looked like I would have to run the diesel truck to about 100,000 miles before I would break even. So I bought a truck with a gasoline engine.

Bill

Don,

What diesel additive and for what vehicle? Isn't your RV gas? Is it because of your cold winters?

Yup, but if you put DEF in the diesel tank, you will likely be buying a new engine.

It goes in a separate tank and is injected DOWNSTREAM of the engine.

az99 wrote:
If you are adding DEF to the diesel fuel you are doing something very wrong.

Well .... I believe that the year 2009 on up diesel Sprinter chassis requires that some kind of "special fluid" be replenished around every 10K miles.

Supposedly this fluid is blue in color and very expensive. I don't know if it's called "DEF", though.

AprilWhine wrote:

az99 wrote:

pianotuna wrote:
Hi,

Then there is the cost of additives for each tank of diesel burned.

What additives? I don't use additives in my diesel.

Late model diesel engines require DEF.

If you are adding DEF to the diesel fuel you are doing something very wrong. :)

AprilWhine wrote:

az99 wrote:

pianotuna wrote:
Hi,

Then there is the cost of additives for each tank of diesel burned.

What additives? I don't use additives in my diesel.

Late model diesel engines require DEF.

Not sure I would consider DEF a diesel additive. I go through an $8-$10 tank of DEF every 6 or 7 fill-ups. Hardly worth mentioning. My heavy right foot costs me more.