Going from Gas To Diesel(?)

[BEisler]

Ok, I am sure this has been bantered about quite a bit but thought I would start a new thread on this that may compile a lot of good input all in one thread.

I am close to making the move from gas to diesel (pusher). What do I need to know about the operation, maintenance and idiosyncrasies, etc. in making this change? For example, in cold weather do I need put a fuel additive in to keep the diesel from gelling (I believe this was an issue many years ago).

Some things I heave gleaned just from scanning previous posts are that diesel can be a little more costly for maintenance but easier to drive with much better handling.

Whatever you can think of that a diesel newbie should know - please share!

[WILDEBILL308]

Yes the DEF filler is on the right side. I did see several coaches at Pilot/Flying J pull to the left of the outside pump lane to fill their DEF tank. Most were able to fill their diesel from the right to. Lets hope the make it where you can fill DEF from either side on the new coaches.
Bill

[holstein13]

JimM68 wrote:
In 2008 / 2009, you get a DPF (diesel particulate filter). Every once ina while it needs to go thru a cleaning cycle (regeneration). No big deal at all unless you are nearly home and approaching your exit. When it goes into regen, you hafta stay on the highway at speed for about 30-40 minutes. It does this maybe twice a year.

In 2010 and up, they have DEF (diesel exhaust fluid) in addition to DPF. So you still have the regen cycles, and also have this little tank of stuff to keep full.

There aren't any more regen cycles. Today's modern engines pretty much regen continuously. Yes, it can happen, but I doubt the typical RVer will ever see a regen light on the dash ever.

[JimM68]

A lot of info in this post!

Just to step back a bit and breath...

The biggest difference I noted when going from a gas Class a to a DP was the quiet.
Second was the smoothness.
Third was how much easier it is to drive.

We roll along in smooth silence. We can talk to eachother if we choose, or listen to the radio, or simply listen to our own thoughts.

Silly details like skinny lanes, passing trucks, bumps, and hills (and mountains) become unimportanmt. Not noticeable. In the background of the experience.

On the emission control thing... Prior to 2008, highway diesels didn't have any ecternal emission control devices.

In 2008 / 2009, you get a DPF (diesel particulate filter). Every once ina while it needs to go thru a cleaning cycle (regeneration). No big deal at all unless you are nearly home and approaching your exit. When it goes into regen, you hafta stay on the highway at speed for about 30-40 minutes. It does this maybe twice a year.

In 2010 and up, they have DEF (diesel exhaust fluid) in addition to DPF. So you still have the regen cycles, and also have this little tank of stuff to keep full.

Neither is a huge deal, and the highway is no longer full of smoking diesels!

[Mr_Mark1]

BEisler wrote:
I appreciate the debate regarding HP, but I have pretty much landed on going with the larger 340HP Cummins. Hopefully I will be more than satisfied.

Now, next questions. . . . can you educate me on the DEF tank? What is it? What does it do? What do I need to do with it? I googled it but always enjoy the practitioner input I get on this forum! Thanks

I think Holstein pretty much summed it up. Luckily, our chassis manufacturer just recently moved our DEF tank filler to the driver's side from the passenger rear location. So, we can fill at the truck pumps with ease.

Our DEF filler is behind the same door as the diesel filler right above and below each other. The diesel filler has a brass cover whereas the DEF has a blue plastic cover. You cannot put Diesel in the DEF tank because the opening is about as round as a quarter.

On the other hand, you could put the small DEF nozzle into the Diesel filler by mistake as it would fit. YOU DON'T WANT TO EVER DO THAT!
DEF in the engine would seize the fuel system up in a few miles. The whole fuel system would need to be replaced which could run close to $15,000 from what I've read.

As with anything, a mistake could happen but the fuel companies make it very obvious that each fuel handle is different and confusing them would be difficult.

I've only filled with DEF once in our new coach. We have a 16 gallon tank and I drove 2,300 miles on the first tank putting in just under 15 gallons. Looking at the receipt, it was $2.79 a gallon a month ago.

We have a 230 gallon fuel tank so I start looking for fuel at 1/2 a tank and try not to go below 1/4. I did let the DEF tank get fairly close to EMPTY but not close enough for any lights or warnings to come on.

Safe travels,
MM.

[Mr_Mark1]

Cbones wrote:

predawn wrote:

Cbones wrote:
I will throw my 2 cents into this thread. I have driven over 90K miles on my ISB equipped Discovery loaded to 32K lbs with a 5K Jeep Grand Cherokee toad. There is no mountain in this country that I could not top. I can run 70 mph all day long pass semis up mountains with ease. Sure I have driven an ISL equipped Revolution, and yes it has slightly more power, but nothing crazy. I travel in tandem with my buddy in his Revo with the ISL. I have absolutely no problem keeping up with him. These are not meant to be race cars. They are just designed to get you from A to B. Almost all motorhomes gas or diesel will get you where you want to go. I would worry less about the size of the engine than the features that you are looking for. There are thousands of Discovery's, Phaetons, and Ventanas out there with ISBs that run all over this beautiful country without any problems getting up all the big hills west to east.

You absolutely can not run 70MPH all day long passing semis up mountains with ease

Evidently a missing comma. The statement should have been ' I can run 70 mph all day long, and yes I can pass semis going up long grades.' I almost always will pass semis in the climbing lane. The point of the post was that most mhs usually have enough power to get you from A-B. If you are looking for the power to weight ratio of an automobile, there is almost no coach that will outperform a typical run of the mill 4 cylinder auto. Additionally, I have never had a problem keeping up with my buddy and his ISL equipped Revolution. Remember his coach is saddled with an additional 10K pounds to carry around.

Cbones, I'm glad that you clarified your post because I would probably would have breezed by any future posts thinking you were full of cupcakes. Now, I understand what you are saying. :C

Safe travels,
MM.

[holstein13]

BEisler wrote:
Now, next questions. . . . can you educate me on the DEF tank? What is it? What does it do? What do I need to do with it? I googled it but always enjoy the practitioner input I get on this forum! Thanks

Wolfe explained some of it, but let me elaborate. My DEF consumption is 3% compared to the diesel, not 2%. I've read that "normal" is between 2 and 3%. The DEF is sprayed directly into the exhaust fumes in the exhaust system and helps reduce the NOx emissions. There is a DEF gauge in the dashboard and when you run low, the engine will go into "limp" mode until you can refill it. Basically, you can't run without it.

My DEF tank and the DEF tank on most RVs is on the passenger side of the coach near the exhaust. Mine holds about 10 gallons of DEF fluid.

Walmart and the truck stops sell DEF in 2.5 gallon containers. These containers are cheapish plastic with an outer cardboard box, but they all have a nice funnel you can attach that makes it super easy and clean to pour the DEF fluid into your tank.

The 2.5 gallon DEF boxes cost about $14.00 each. Which is about double what you'll pay for bulk DEF. So you basically have two choices on how to fill your DEF.

1) You could order the 2.5 gallon boxes of DEF at Amazon.com using prime or pick up a box or two at Walmart / Auto parts / Flying J, etc. and you can fill your tank at your leisure. or

2) You could fill up in bulk at the truck stop. Unfortunately, the DEF dispenser is only on the driver's side of the coach. Therefore, you must either back into your lane (which can be tricky given the design and traffic patterns at a truck stop) or you can carry a portable container and fill it up at the dispenser and then walk it back to your DEF tank and pour it in.

The second choice is what I do because it's cheaper and I'm at the truck stop anyway but there are some things to keep in mind. The first is that pouring bulk DEF from the dispenser into a portable tank and then into your DEF tank can be messy and slow. You don't need to worry about toxicity because DEF fluid is basically fertilizer. It dries into a salt. So if you get any on you and don't rinse it off, you'll eventually notice little salt buildups on your skin or clothes. The second thing to consider is the design and size of your portable tank. I've been using a collapsible 2.5 gallon jug with a separate funnel and I hate it. As soon as I find a nice rigid 3 gallon tank with a nozzle, I'll replace mine.

Finally, I have found that I've got to pay for my fuel and my DEF separately. In other words, I go in and hand the attendant my credit card, then go back in and pick up my fuel receipt and tell them to keep the card for a DEF fill up. After filling up with DEF, I have to go back in and retrieve my card and receipt.

I've got to believe there is a card that works outside to activate the pump, but I haven't been motivated to apply for a fuel card yet. It's on my list.

Hopefully, this answers your questions.

[JetAonly]

BEisler wrote:

holstein13 wrote:
Ignoring the question of adequate power, here are some of the differences I've noted when I switched from Gas to Diesel.

1. Diesel fuel is more expensive than gasoline and this may or may not be offset by better mileage. Mine isn't, but my coach alone is close to 54,000 pounds.
   
2. I now fuel up at the truck stop diesel pumps. I've got a 200 gallon tank and filling it up at the car pump at 10 gallons per minute would take 20 minutes.
   
3. I now have to fill a DEF tank that I didn't have to do with a gasser. Every other fuel fill up requires me to top off the DEF tank. And it's on the wrong side of the coach.
   
4. My fuel fill inlet is right behind my driver's seat so it's very easy to gauge where to stop at the pump. I can fill from either side.
   
5. Air brakes are super easy to operate. Takes less pressure to engage than my old hydraulic brakes.
   
6. The ride is very quite up front. It's a night and day difference. I can easily have conversations with my wife (although we rarely do) or listen to music or anything else.
   
7. The air ride suspension is much nicer than my old suspension. 95 percent of the bumps and potholes are easily absorbed by the suspension.
   
8. I need to air up my coach and let the ride height come up before leaving. I make sure my ride height is adequate by walking around the coach and checking when I first start up.
   
9. Conversely when I stop the coach and put down the jacks, I need to make sure the tires are straight so that the wheel wells don't come crashing down on the tires.
   
10. If I tried to make a turn before the coach was at ride height, I would surely damage the tire wells. I've witnessed it on another coach.
    
11. When I want to let the coach idle, I must bring the idle up to 1,000 RPM to prevent damage to the motor.
    
12. I just bought a fuel filter for the coach to keep as a backup and it cost me over $100.00
    
13. I'm told that bad fuel is a real possibility with diesels
    
14. My air filter has a gauge that tells me if it's dirty and needs to be replaced.
    
15. My coach is equipped with a supplemental air leveling system that keeps it level on roads with a crown or curves. I can even level and put out the slides using this system without the jacks.
    
16. My alternator is so powerful it can even keep the batteries charged while one roof AC is running. No need to run the generator on route.
    
17. My generator is now diesel as well and takes a few seconds to warm up when I press start.
    
18. I've got an engine block heater installed but am told I wouldn't need it unless temps drop dramatically below freezing at departure time.
    
19. My engine and transmission weigh about 7,000 pounds alone. Everything on this engine is huge, especially the air filter and exhaust system.
    
20. Each cylinder puts out 100 horsepower.
    
21. My air horns sound dramatically different than my old electric horn. It's more like a train now and gets people's attention.
    
22. My coach came with a diesel hydronic heating system that keeps my shower hot no matter how long I run it. It uses engine heat while on route to heat the furnace.
    
23. The parking brake is a plastic knob that I must pull to activate. It can hurt my hand to pull on it because it has a percussive effect.
    
24. There are only three buttons on my transmission R N and D. There is also an up/down arrow and an eco mode but I never use either.
    
25. To park, I put my foot on the brake, put the transmission in Neutral, apply the air parking brake and then release my foot from the service brake in that order. Otherwise an alarm sounds.
    
26. To get moving again, I put my foot on the service brake, release the parking brake, then put the transmission into gear in that order. Otherwise an alarm sounds.
    
27. The engine seems to be as easy to start and stop as my old gasser. I pause for a few seconds before starting it to allow the glow plugs to light up.
    
28. The entry door is now in the front of the coach so I walk around the passenger seat every time I enter the coach. It was less awkward in the old gas coach. Also, the door needs to be slammed before departure to make sure it is properly sealed against wind noise.
    
29. There are truck repair shops virtually everywhere along the major highways. Lot's of official Cummins authorized service centers as well. They are easy to get in and out of.

I hope this gives you some of the insights you were looking for. It's a shame that the horsepower issue keeps getting debated endlessly on this forum.

Wow, this post is EXACTLY the input I was looking for. I cannot thank you enough. And all of the other posts were super helpful as well. I am all eyes if anyone has anything to add. THANK YOU SO MUCH.

As an update, I am now looking at the same model RV as I was looking at before, but with a 340HP Cummins - much more comforting for me.

I would be very careful about how you draw conclusions from this comparison. An ISB powered Coach and an ISX powered Coach are very different animals aside from their fuel requirement and the $500k or $600k difference in price.

[wolfe10]

DEF= Diesel Exhaust Fluid

It is available at Walmart, etc and at many truck stops at the pumps (separate pump from diesel).

It is injected downstream of the engine and assists the emissions system in breaking down harmful NOx.

You consume roughly 2% as much DEF as diesel fuel.

[BEisler]

I appreciate the debate regarding HP, but I have pretty much landed on going with the larger 340HP Cummins. Hopefully I will be more than satisfied.

Now, next questions. . . . can you educate me on the DEF tank? What is it? What does it do? What do I need to do with it? I googled it but always enjoy the practitioner input I get on this forum! Thanks

[Cbones]

predawn wrote:

Cbones wrote:
I will throw my 2 cents into this thread. I have driven over 90K miles on my ISB equipped Discovery loaded to 32K lbs with a 5K Jeep Grand Cherokee toad. There is no mountain in this country that I could not top. I can run 70 mph all day long pass semis up mountains with ease. Sure I have driven an ISL equipped Revolution, and yes it has slightly more power, but nothing crazy. I travel in tandem with my buddy in his Revo with the ISL. I have absolutely no problem keeping up with him. These are not meant to be race cars. They are just designed to get you from A to B. Almost all motorhomes gas or diesel will get you where you want to go. I would worry less about the size of the engine than the features that you are looking for. There are thousands of Discovery's, Phaetons, and Ventanas out there with ISBs that run all over this beautiful country without any problems getting up all the big hills west to east.

You absolutely can not run 70MPH all day long passing semis up mountains with ease

Evidently a missing comma. The statement should have been ' I can run 70 mph all day long, and yes I can pass semis going up long grades.' I almost always will pass semis in the climbing lane. The point of the post was that most mhs usually have enough power to get you from A-B. If you are looking for the power to weight ratio of an automobile, there is almost no coach that will outperform a typical run of the mill 4 cylinder auto. Additionally, I have never had a problem keeping up with my buddy and his ISL equipped Revolution. Remember his coach is saddled with an additional 10K pounds to carry around.

[Mr_Mark1]

predawn wrote:

Cbones wrote:
I will throw my 2 cents into this thread. I have driven over 90K miles on my ISB equipped Discovery loaded to 32K lbs with a 5K Jeep Grand Cherokee toad. There is no mountain in this country that I could not top. I can run 70 mph all day long pass semis up mountains with ease. Sure I have driven an ISL equipped Revolution, and yes it has slightly more power, but nothing crazy. I travel in tandem with my buddy in his Revo with the ISL. I have absolutely no problem keeping up with him. These are not meant to be race cars. They are just designed to get you from A to B. Almost all motorhomes gas or diesel will get you where you want to go. I would worry less about the size of the engine than the features that you are looking for. There are thousands of Discovery's, Phaetons, and Ventanas out there with ISBs that run all over this beautiful country without any problems getting up all the big hills west to east.

You absolutely can not run 70MPH all day long passing semis up mountains with ease

Well, I knew the story was being stretched a little. There is no way a motorhome can do 70 in mountain passes with a small ISB (and I'm not even a gear head). My knowledge comes from experience. I followed my friends who had a Monaco Signature with the 600 HP Cummins and they could pull better than me with my 425 ISL, but not by leaps and bounds. I weighed 40,000 lbs, they weighed about 50,000 lbs.

I know how to read between the lines.:R

MM.

[predawn]

Cbones wrote:
I will throw my 2 cents into this thread. I have driven over 90K miles on my ISB equipped Discovery loaded to 32K lbs with a 5K Jeep Grand Cherokee toad. There is no mountain in this country that I could not top. I can run 70 mph all day long pass semis up mountains with ease. Sure I have driven an ISL equipped Revolution, and yes it has slightly more power, but nothing crazy. I travel in tandem with my buddy in his Revo with the ISL. I have absolutely no problem keeping up with him. These are not meant to be race cars. They are just designed to get you from A to B. Almost all motorhomes gas or diesel will get you where you want to go. I would worry less about the size of the engine than the features that you are looking for. There are thousands of Discovery's, Phaetons, and Ventanas out there with ISBs that run all over this beautiful country without any problems getting up all the big hills west to east.

You absolutely can not run 70MPH all day long passing semis up mountains with ease

[BEisler]

holstein13 wrote:
Ignoring the question of adequate power, here are some of the differences I've noted when I switched from Gas to Diesel.

1. Diesel fuel is more expensive than gasoline and this may or may not be offset by better mileage. Mine isn't, but my coach alone is close to 54,000 pounds.
   
2. I now fuel up at the truck stop diesel pumps. I've got a 200 gallon tank and filling it up at the car pump at 10 gallons per minute would take 20 minutes.
   
3. I now have to fill a DEF tank that I didn't have to do with a gasser. Every other fuel fill up requires me to top off the DEF tank. And it's on the wrong side of the coach.
   
4. My fuel fill inlet is right behind my driver's seat so it's very easy to gauge where to stop at the pump. I can fill from either side.
   
5. Air brakes are super easy to operate. Takes less pressure to engage than my old hydraulic brakes.
   
6. The ride is very quite up front. It's a night and day difference. I can easily have conversations with my wife (although we rarely do) or listen to music or anything else.
   
7. The air ride suspension is much nicer than my old suspension. 95 percent of the bumps and potholes are easily absorbed by the suspension.
   
8. I need to air up my coach and let the ride height come up before leaving. I make sure my ride height is adequate by walking around the coach and checking when I first start up.
   
9. Conversely when I stop the coach and put down the jacks, I need to make sure the tires are straight so that the wheel wells don't come crashing down on the tires.
   
10. If I tried to make a turn before the coach was at ride height, I would surely damage the tire wells. I've witnessed it on another coach.
    
11. When I want to let the coach idle, I must bring the idle up to 1,000 RPM to prevent damage to the motor.
    
12. I just bought a fuel filter for the coach to keep as a backup and it cost me over $100.00
    
13. I'm told that bad fuel is a real possibility with diesels
    
14. My air filter has a gauge that tells me if it's dirty and needs to be replaced.
    
15. My coach is equipped with a supplemental air leveling system that keeps it level on roads with a crown or curves. I can even level and put out the slides using this system without the jacks.
    
16. My alternator is so powerful it can even keep the batteries charged while one roof AC is running. No need to run the generator on route.
    
17. My generator is now diesel as well and takes a few seconds to warm up when I press start.
    
18. I've got an engine block heater installed but am told I wouldn't need it unless temps drop dramatically below freezing at departure time.
    
19. My engine and transmission weigh about 7,000 pounds alone. Everything on this engine is huge, especially the air filter and exhaust system.
    
20. Each cylinder puts out 100 horsepower.
    
21. My air horns sound dramatically different than my old electric horn. It's more like a train now and gets people's attention.
    
22. My coach came with a diesel hydronic heating system that keeps my shower hot no matter how long I run it. It uses engine heat while on route to heat the furnace.
    
23. The parking brake is a plastic knob that I must pull to activate. It can hurt my hand to pull on it because it has a percussive effect.
    
24. There are only three buttons on my transmission R N and D. There is also an up/down arrow and an eco mode but I never use either.
    
25. To park, I put my foot on the brake, put the transmission in Neutral, apply the air parking brake and then release my foot from the service brake in that order. Otherwise an alarm sounds.
    
26. To get moving again, I put my foot on the service brake, release the parking brake, then put the transmission into gear in that order. Otherwise an alarm sounds.
    
27. The engine seems to be as easy to start and stop as my old gasser. I pause for a few seconds before starting it to allow the glow plugs to light up.
    
28. The entry door is now in the front of the coach so I walk around the passenger seat every time I enter the coach. It was less awkward in the old gas coach. Also, the door needs to be slammed before departure to make sure it is properly sealed against wind noise.
    
29. There are truck repair shops virtually everywhere along the major highways. Lot's of official Cummins authorized service centers as well. They are easy to get in and out of.

I hope this gives you some of the insights you were looking for. It's a shame that the horsepower issue keeps getting debated endlessly on this forum.

Wow, this post is EXACTLY the input I was looking for. I cannot thank you enough. And all of the other posts were super helpful as well. I am all eyes if anyone has anything to add. THANK YOU SO MUCH.

As an update, I am now looking at the same model RV as I was looking at before, but with a 340HP Cummins - much more comforting for me.

[holstein13]

WILDEBILL308 wrote:
holstein13, Just wondering about a couple of things.
“3. I now have to fill a DEF tank that I didn't have to do with a gasser. Every other fuel fill up requires me to top off the DEF tank. And it's on the wrong side of the coach.”
4. My fuel fill inlet is right behind my driver's seat so it's very easy to gauge where to stop at the pump. I can fill from either side.”

Why since you can fill from either side don’t you fill from the side the DEF tank is on?

24. “There are only three buttons on my transmission R N and D. There is also an up/down arrow and an eco mode but I never use either.”

That is ECON button and it will improve your mileage. Not knowing how and when to use those arrows may contribute to damage to your engine. It could also degrade your safety.

Although I can add diesel fuel from either side, the DEF dispenser is only on the driver's side. Unfortunately, my tank is on the passenger side.

As to the eco mode on the transmission, I've posted about this before. I've noticed virtually no difference when I use it and this was confirmed by many posts on this forum. The button is meant to hold a higher gear longer thereby reducing fuel consumption. In my case, I've got close to 2,000 foot pounds of torque and my engine never downshifts on rolling hills or small inclines. I'm in high gear virtually all the time.

In short, with an engine my size, there is simply not the need for or benefit of the eco button like there would be on a smaller engine. But it's built into the Allison 4000 transmission so we get it anyway.