Diesel Mileage

I would think the most useful purpose in estimating fuel usage is simply budgeting mileage between refills.

For example, I know that our coach averages 8.5 over the long haul driving 60 to 65 and has done so since the engine was born 68,000 miles ago. This is a very useful number so I can budget two days of travel between fuel stops, or about 60-70 gallons (1/2 tank). Perhaps 3 days in a pinch. I've seen legs averaging 13 and some averaging 6 but they really don't count as stand-a-lone consumption figures.

With the Silverleaf being dead on for both MPG and fuel burnt you can easily plan stops well in advance.

Cost is what cost is but having information for trip planning is very comforting.

Mileage is something you will hear all sorts of tails about and most of them stretched somewhat. The best we ever got was on I-90 with a strong tail wind. Lightly loaded 36 foot Itasca Horizon (2000) with a 300 Cat engine and a 5 speed Allison towing a Honda Element. Wind blew strong nearly all day and right up the rear of the coach. We got a bit over 9.5 and were very happy. Came across Oklahoma out of Texas one day in the same coach and had a strong head wind all day long. On flat ground the Allison would down shift on the little grades it was so strong. About 6.
I just count fuel costs as part of the price we pay for an expensive hobby. Can't NOT travel, it's too much fun and it don't look like fuel will get any cheaper in my lifetime.

I am averaging 8.2 mpg with Cat 350. 100 gal tank, I start looking for refuel after about 400 miles so I have plenty of miles to stop without panic.

If you are concerned about your MPG you are posting in the wrong place. Fill your tank, drive, fill your tank and do the math. Do this a couple of more times and you will get a pretty good idea of your MPG after about 1000 miles of driving. The difference between getting 8 or 10 MPG will turn out to have cost you less than $100 over that 1000 mile trek. That being the case, how important is your MPG?

Double Post

There are just TOO MANY variables to compare mileage on a DP. The only real estimate anyone can provide will be 8 mpg plus or minus 3 mpg depending on your coach and driving habits.

We had a short/lite 2005 Monaco Diplomat (36') with a 400 ISL. I changed the rear radiator engine fan, added a computer chip and used a fuel additive. It was the last year for shorter tires on the Diplomats and my rpm at 58 mph was 1500. With that specific setup, we got 9.4 mpg towing a 4 door Silverado coast to coast and back. Without the truck in tow, we could get 10.1 -10.2 mpg. Again, this was at 58 mph.

We now have a 2014 40' with the ISL and a tag. On our first big trip, not towing and running 58 mph, we got 8.3 mpg. We did climb a lot of hills and hit heavy winds on 3/4ths of the trip. I have high hopes to get 9 mpg in better conditions and after break in.

The biggest denominator is speed....once you get past 60 mph, mileage drops off rapidly.

I can get 10 mpg with my ISL 400 BUT I have to go 45 mph. At 65 it's 7 but with a good tail wind it's 8 but I end up not going where I wanted to go if I keep the wind at my back. With a good head wind I'll loose 1 mpg. 70K mile average is 6.9 and I'm on the heavy side plus the right foot is heavy too.

Double post

Busskipper wrote:

Dakota Wagon Master wrote:
Recently purchased a 2006 Tradewinds 60D with the 400 HP Cummins and Alison transmission. I have heard of mileage reports of 8-12 mpg.
What's real?!

Real Life experiences here;
70 mph = 7
65 with the wind maybe 7.3-7.5
60 on cruse control flat 7.8-8.0
55 cruse control and the wind at your back maybe 8.2 - 8.5
Top of Vail Pass to Golden with engine break used sparingly 10 - 12

Those people who say they get 12 in a ISL 400 going down the Highway are just a little Math Challenged.

JMHO,

Yeah, can't say I've heard of 12mpg on any. I do have to say that I really do love my little 300 Cummins with the Alison 5 speed combo. I get a pretty consistent 7.6-7.9 mpg with anything faster than 67mph pulling my 20' car hauler loaded total weight ~6k pounds. I have confirmed many, many, many times now that if I will just drop to 64mph with cruise, I get a consistent 10.5-10.9 mpg.

If you are selling one the answer is 10-12
If you are buying one the answer is 5-7
If you are using one the answer is 7-9