I kept all of last year diesel purchase receipts and finally had time to calculate my average milleage.

My average milleage for the entire year is 11.7 miles per US gallon.

Is that the norm for a 190HP Cummins?
My average cruising speed is 60 MPH.

We just got back from a 900 mile trip from Center of Washington off I-5 to the Eastern California border and going down we climbed from 300 feet to 4800 feet and averaged 10.1 at 60 to 65 mph. Coming home, we averaged 11.6 as we were dropping back down to 300 feet, and at the same speed. Ours is a 33' Breakaway with the cummins 5.9 and an allison 6 speed.
Darrell and Jeannie

I have averaged right at 10.4 MPG for over 20K miles, with receipts. I fill up and even thou it takes twenty minutes, I fill to the same level in the neck everytime. Of course, over many miles the inaccuracy gets less so I am confident that my numbers are very accurate. Many of the routes that I drive to the various functions that I participate in are the same, same time of the year, same temperature, so I can tell right away if the mileage varies, It hasn't--until this trip!

I learned from a friend that does diesel performance tuning that they use a bit of 2 stroke oil as an additive and they get a bit better mileage. Well-- I tried it and I have--

So far this trip, I have averaged almost 10.9 MPG. This includes a run from Tucson to Phoenix in a head/left quartering wind of 25-40 MPH. The Barth shook a bit but wasn't nearly as bad as I expected it could have been. I averaged just a shade under 10 MPG for that portion of the trip. I am seeing over 11 MPG regularly now.

I drive 70 MPH. (I tried to start out slow this trip but that lasted less then 25 miles!)

My engine is the bigger brother of yours, 230 HP and 6 speed.

I have seen other reports of the 190 HP doing in the 11s and 12s so your numbers seem to be in line with most.

Hi Ed,
What ratio did you mix the 2 stroke oil and fuel?

About two years ago, I averaged 10 mpg for a round trip to CA from MS or about 7000 miles. I drove 65 most of the way but later discovered that the speedometer is fast. When it shows 65 it is really going 60 (according to the GPS). This probably means that the mileage is something less than 10mpg. Based on some other discussions I've seen on this site, I suspect there may be many other units out there with the same speedometer error. Even with the speedo error, the odometer may still be correct. I have not double checked it yet --- against mile markers on a long stretch of road.

Even if it is less than 10mpg, I am still very happy. I had a 25 ft class C with a 460 Ford that never got over 6/7mpg and my Barth, which probably weighs twice as much as the Ford, still gets better mileage.

When I first got my coach, one of the first things I checked and found against the GPS and similar thing, but, not quite as bad as yours. Mine was showing 65 and I was actually doing 62. The odometer does follow the speed reading on the VDO speedometer, so if the speedometer is fast, the odometer will be accumulating more then actual miles.

I reset the speedometer and I have been reading exactly what the GPS shows for the last 30K miles. I am starting to see a very slight difference now as the tires have worn abit. Tires have about 25K miles on them.

I also take a lot of time to re-fill, the fill line goes into the middle of the tank and I will keep filling until I have fuel standing in the neck everytime, that way I have an exact reference for mileage, and of course after many, many fills, any small filling error averages out.

MY calculation method: Coach gets 8mpg (at 67mph) while towing a 6,000lb toad: toad gets 13mpg; so actual mpg on trips is 10.5!

This is for Ed. You say you fill right to the neck every time. Is diesel fuel less prone to expansion than gas? If I fill the right tank just till it trips the filler, I have to run out 10 miles or so just to avoid overflow and filling the coach with the smell of gas. On long trips I do this, then switch back to the rear,[main] tank so the gauge works. This may seam like nonsense, but it works.

The nearest fuel station for me is about 10 miles from home. If I fill to the neck, by the time I reach home there is about 1 gallon used. I don't think I have ever filled up to the neck and let the coach sit. I only have 1 tank.

Never had any trouble with overflow or diesel smell after filling.

Over 12,000 miles I averaged 9.8mpg.

Since the transmission and injector swapouts, I am now running 11.25 over the past 2000 miles. What is interesting is that I seem to be getting the same mileage at 68 as 58. Might be that at 58 the RPMs are under 1600 and 1750 at 68. Still just below the max torque.

But man can I now climb hills.

With the old 190HP 6.5L TD, I averaged around 9.25 mpg, running at 60. With the new 230HP AMG engine with hi-pop injectiors and a non-waste-gated turbo, mileage increased to 10.1. With the transmission rebuild last month, the 2,200 mile round trip to NY yielded around 11.2.