C 12 505 fuel efficiency

[David T. Richelderfer]

Our coach has trouble averaging 5 mpg.  Since we have no interest in knowing how much fuel goes through the generator, we simply figure the mileage by "gallons put in the tank divided by miles driven."  We sit in Yuma all Winter using the diesel burner to make hot water and all that diesel usage without one mile driven makes our first fill after winter show awfully poor mileage.  lol

We decided several years ago that if spending money on fuel is a concern, then don't own a Beaver... or any larger motorhome, for that matter.

[Phil N Barb Rodriguez]

We don't mind spending money on diesel but I do like to optimize our mileage. One of the lines I choose to put on the silver leaf is rolling MPG. I find that being attentive of rolling MPG lets me find the sweet spot for mpg when in a windy area or on a long uphill grade, and when to kick off the cruise control. Also helps to control engine and tranny temps with my right foot. I drive in the 60-70 mph range, when on "good roads" when out of the mountains and light to no winds.

On our 6600 mile round trip last year from Spokane to New England in our '03 Country Coach Magna, C-12, 505hp, w/tag and towing our '97 Cherokee we averaged 8.4 mpg. That is according to the silver leaf and verifying by math, miles driven and gallons into the tank. We physically did that on around 6 fill ups on the trip.

On a 3k mile round trip this year from Spokane to SoCal we averaged 8.9mph into SoCal and an average of 8.4mpg into Spokane. It's a big advantage going downhill from Dillon, Mt into Vegas but you pay it back on the return trip climbing from Vegas into Montana.

The difference in the two trips was changing our toad from a Jeep to a 2014 Toyota FJ, the FJ is 400 lbs heavier.

In our previous 2000 Beaver Thunder C-12, 425hp, we typically saw mileage in the mid 9's. I used synthetics in the engine, tranny, and differential on both coaches, and a fuel additive that contains several points of Cetane. Tires are 6 Toyos on the rear and Michelins on the front.

Doing this keeps me awake....

Phil

[Gerald Farris]

Robert,
Of course, your fuel mileage will vary depending on your driving habits (speed and acceleration rates), coach weight, wind resistance, and terrain (hills,mountains, or head winds), but the entire line of C 12 engines in Beaver coaches from the 425 HP to the 505 HP version will give better performance and fuel mileage than any other big block engine. I have been driving a C 12 powered Beaver for the last 15 years, a 425 HP 2000 Marquis a 505HP 2002 Solitaire, and I have averaged from 8 to 8.5 on the 39,000 lb. Marquis to 7.5 to 8 on the 50,000 lb. Solitaire that is 13.5 feet tall. Another comment about the C 12 is that in about 200,000 miles of driving one, I have found the engines to be almost bullet proof.

Gerald

[Mike Shumack]

I wonder what CAT did, regarding engine design, that resulted in the C13 getting 2 mpg less (on a similar size/weight coach) than the C12? That's a 25% drop in fuel economy.
The engine displacement is only 5% different (732 cu-in versus 763 cu-in)

[Gerald Farris]

Mike,
The C 12 would not meet the federal government upcoming emission standards, so the C 13 was built to meet those standards. The C 13 is a different engine design and not a slightly modified C 12. You can blame the 25% reduction in fuel mileage on the federal government. The biggest difference between the 2 engines is the redesigned cylinder head, dual turbo chargers, and operating program that uses different fuel mapping.

Gerald

[Doug Allman]

For those that may ever think of changing coach's you will possibly have to move out of the Beaver to some other brand if a newer coach. With that move you will almost always have to go to a Cummins in a Class A. That did not thrill us as we had the C-12 in our 2004 Marquis and I was sure a Cummins would not get the same performance.
To date we now have close to 30,000 miles on our 2017 Entegra Cornerstone with the 600 hp Cummins and we could not be happier. Its performance is excellent for a coach that weighs 58,000 lbs towing an F-150 pickup most always fully loaded with firewood and other items.
It's sweet spot is at 75 mph on the Interstate where it just seems to drive the best and run the smoothest. If it is windy it handles the road impeccably better at higher speeds than it does if you are in the 60 mph ranges.
The read out on mileage started at 6.5 miles per gallon and it is still at 6.5 so I have no idea if it is working or not. Just fill it when it needs it. A dream to drive.
It also has the Tag axle that turns and makes getting into and out of places we would never even consider with our Marquis. I have had the dear wife on numerous occasions say "you cannot get in there" and we did and back out again without bending anything, and its 45' long not 40'.

Yes it takes some green but all in all would do it over again. The Cummins has performed exceptionally well in all aspects from the flat land to the mountains back and forth across the US. It just likes a large drink every now and then.

[Mike Shumack]

Hi Doug, I'm glad you are enjoying your Entegra. I don't want to rain on your parade but if you have the Cummins ISX engine, you should check out the discussion of Cummins ISX Broken Valve on the irv2. I think your engine is new enough that it has the updated parts (valves, heads, pistons, etc.).
(Note from admin; can't post links to other forum w/o original poster's permission).

[Doug Allman]

Mike, From all I have seen it is on motors I believe pre 2010 but in any regard the Spartan chassis info has a note that you should run your engine every month up until it gets fully to operating temperature for coachs that are sitting for long periods. Believe your info was answer to this situation that I did not know about.

However, as posted about Oil Analysis this is a critical very economical way to detect most all potential problems internally with an engine so that an owner can address them prior to the end result of a failure. Oil Analysis, dependent on miles driven a year, can be done yearly and give at first analysis a baseline for the engine, then it becomes a point to compare the next analysis against. You get a very clear look at what is going on internally. There is never a point that starting this baseline and then doing future analysis is not worthwhile to the Owner.

Because we have the 600 ISL Cummins we have already started oil analysis and have the report back form 1 lab. We are doing 3 different labs on each oil change. 1 with AMSOIL as we use their synthetic, 1 with CAT as they have an excellent lab that can determine what the metallurgy is should they find any metallic particles (CAT lab knows what all the metallic components are for the bolt on parts to their engines so they can pinpoint that part with the metallurgy analysis), 1 with a lab that Cummins recommends (We are still trying to get info from Cummins to see if they know like CAT does what the metallurgy is on all their bolt on parts).

At the worst it is about $75.00 to do 3 oil samples a year. With an engine worth somewhere north of $60,000 this sampling cost is a pittance compared to any other cost to keep this engine running. Even if you only do the CAT sampling on your used CAT engine at around $20.00 for the sample kit the piece of mind you get from knowing the health of your engine is very comforting. If it points to a future problem address it or make a decision on how to move to another coach. If you are going to sell and the tests indicates the engines good health that is a deal maker.

As most Forum comments will reflect there is much gnashing of teeth when you have a major warranty problem on a diesel engine. Any excuse will do to try and get out of that warranty either by the engine maker or an extended warranty company. That is the reason why we are using 3 lab reports to verify information on this 600 ISL Cummins.

Just because you have oil change receipts does not pass the final test to get either of them to take responsibility and do the necessary repairs.

By the way we are also having Dave Atherton run the Cummins Insite program as well as review all our oil samples. The BAC has the Diesel Diagnostics guy that numerous other clubs are trying to get, dont miss out on using this extremely valuable asset we have. I am not any smarter than any other coach owner and thanks to Dave I know a lot more than I ever used to about a diesel engine. You can too to protect your investment.

Merry Christmas to all.

[Dave Atherton]

Mike,
Yes I agree Caterpillar engines are very good long life low maintenance cost engines with proper service. There are several models that stand out better than others and whose track records have been followed by Caterpillar Off Road and show long life and low operation cost. Many of these engines were sold to the R.V. industry prior to CAT's exit from the over the road business. However these engines are still in service and built today so we as R.V. owners have nothing to worry about. These engines or parts are available for your motorhome engine if needed.
I wanted to touch on why the C-13 engine had been chosen for on-road truck. The design of this engine can give a very broad range of engine horse power models where other models could not. As for one model Caterpillar  engine that is stands out ahead of other models that I think it is down to owner preference  and how he or she drives and maintains engine. When we get feedback about mileage in the high 200,000 mile range with little problems that is normal and expected for a diesel engine. You as an owner will not wear out your Caterpillar engine.
Wishing everyone a Merry Christmas and let’s look forward to happy travels.
Dave Atherton Retired Cat Mechanic