Class C Diesel MPG Question

hsteveberry wrote:
We have a 2015 Jayco Seneca 37HJ and our milage so far is:

Flatlands of FL, LA, AND TX = 9.5 to 10.5
Hill country of AL, GA and MS = 8.5 to 9.5

The unit is still fairly new so the milage might change with more miles.

*How fast do you run?
*Fuel economy doesn't improve with age or miles.
*Is this a diesel?

We have a 2015 Jayco Seneca 37HJ and our milage so far is:

Flatlands of FL, LA, AND TX = 9.5 to 10.5
Hill country of AL, GA and MS = 8.5 to 9.5

The unit is still fairly new so the milage might change with more miles.

You ask for diesel mileage numbers, try 8.5mpg. On an ’06 Seneca 34SS DMax Super C towing at 62/65 in CA and faster in the rest of the west, uphill and down the numbers all average 8.5 at 23,900lbs including the car on a dolly. The low was 6.8 over 500 miles west across Kansas into a wind and 10.4 for 600 miles east on I-40 with the wind. Your mileage may differ at lower speeds but the tank holds 80 gal. and I spend them frivolously.

Explorer1016 wrote:
The major problems with the 6.0 were from head bolts and those caused head gasket issues and that caused coolant issues and EGR cooler leaks and so on.
The 6.7 is still not a match for the DuraMax. GM has bought out Isuzu's stake in the Dmax and it has been the same engine since 2000 with the Allison 1000 trany. Ford has gone through 4 diesels to try to match the DMax and the Cummins. I only have a Ford because of the type of RV'ing we do and needed 4x4, otherwise I would have stayed with a GM product.

I owned 3 DMax pickups (2000, 2006, 2011) I drove a cumulative mileage of almost 400,000 miles towing and working those trucks. The biggest problem I had was with the 2006. Had to replace injectors but it was a warranty issue. Really didn't have to spend money for any other repair issues.


If Ford can keep the 6.7 on the road for 15 years without any issues then it can be said it is a great engine. Right now GM and Cummins are way ahead of Ford in the reliability department.

Also, the 6.7L PSD is rumored to be the most expensive engine build in the market trying to meet emmisions.

x 2 The basic design flaw/limiting factor of the 6.0 and 6.4 Navistar sourced engines is that they are built with only 4 head bolts around each hole as opposed to the 6 bolts found in most medium duty diesels such as the B Series Cummins or the Duramax.

The aftermarket has come out with stud kits and improved head gaskets which will allow the 6.0 and 6.4L Navistars to live much longer, and EGR delete kits (which may adversly affect vehicle emissions) to improve reliability.

There are several Fords around here which have had a B Series Cummins transplanted, in fact the aftermarket is selling kits to simplify the install and interface.

A King Ranch with Cummins power driving the reliable Ford 5 speed Torqshift would be a sweet machine.

j-d wrote:
I agree with all of the above about "Ford" diesel engines. IIRC, if you check specs, you'll find he Van/Class C iteration of the Diesel does NOT produce the HP and Torque everybody brags about in pickups. There are space and cooling issues in the E-Series so the diesel is de-tuned. The V10 performs about like the PSD in a pickup. The V10 will outperform the PSD in a Class C.

I want a Ford Chassis, Cummins Engine, Allison Transmission...

The Ford 7.3 PSD outperforms the Ford gasser V10 in every category that I can think of - IN a Class C.

Which ones are you thinking it performs better in?

J-D good point! I forgot about the detuned PSD engine in the E series vans.

I agree with all of the above about "Ford" diesel engines. IIRC, if you check specs, you'll find he Van/Class C iteration of the Diesel does NOT produce the HP and Torque everybody brags about in pickups. There are space and cooling issues in the E-Series so the diesel is de-tuned. The V10 performs about like the PSD in a pickup. The V10 will outperform the PSD in a Class C.

I want a Ford Chassis, Cummins Engine, Allison Transmission...

The major problems with the 6.0 were from head bolts and those caused head gasket issues and that caused coolant issues and EGR cooler leaks and so on.
The 6.7 is still not a match for the DuraMax. GM has bought out Isuzu's stake in the Dmax and it has been the same engine since 2000 with the Allison 1000 trany. Ford has gone through 4 diesels to try to match the DMax and the Cummins. I only have a Ford because of the type of RV'ing we do and needed 4x4, otherwise I would have stayed with a GM product.

I owned 3 DMax pickups (2000, 2006, 2011) I drove a cumulative mileage of almost 400,000 miles towing and working those trucks. The biggest problem I had was with the 2006. Had to replace injectors but it was a warranty issue. Really didn't have to spend money for any other repair issues.

If Ford can keep the 6.7 on the road for 15 years without any issues then it can be said it is a great engine. Right now GM and Cummins are way ahead of Ford in the reliability department.

Also, the 6.7L PSD is rumored to be the most expensive engine build in the market trying to meet emmisions.

The 2004 Ford had a 6.0 engine that was not a very good engine. The engine is made by Navistar and causes a lot of trouble. When the EPA made Ford and other manufactures down size the cubic inches of the engines Ford worked with Navistar and came up with the 6.0. Needles to say it did not turn out very well. Ford only keep the 6.0 for 4 years while Navistar worked on a new engine, the 6.4. This engine has worked very well but again ford was looking for a new engine for their F-250 and up trucks, which has developed into the 6.7 which is a Ford built engine that they have had for several years in Europe. This is the new engine that Ford is putting in all their new trucks. This is a GREAT engine and will end up being the best on the market.

Sounds like pretty good results. Yes, I need to investigate the details on the engine year and size. It is a 2004 Class C.