Going from Gas To Diesel(?)

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.

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

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.

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.

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.



Bill the Iceman aka the op that 2013 Thor Daybreak is a nice coach. Most of the things you need to know have already ben covered. I would look at a nice used coach as you can find some amazing deals. If you can afford it I would by new enough that you do have a coach that uses DEF. The newer coaches can and are tuned to give more HP and mileage. I don’t know of a builder that makes a coach that doesn’t have enough power.
Your question about additives, I add an antigel as it is cheap insurance. Where I live it is possible to get into cold weather and still have all summer diesel number 2. I got caught by a cold front camping on the top of Raton Pass in NM. It dropped to -5 overnight. I was glad when MY motor started with no problem. You can read your owner’s manual on using the block heater.
Yes owning a diesel coach is a little more expensive. So what owning a gas unit is more expensive than tent camping. I don’t do it because it is cheap I do it because I want to.
Bill

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

I didn't copy everything but...
What an excellent post!

I think predawn is blowing a lot of smoke in this forum. I guess he does not realize that the engineering department will install engines according to the weight of the coaches.

He claims he has the ISL 450 on his coach and can not pass trucks going faster then 70 miles per hour. LOL. Who wants to be driving up a six percent grade going 70 miles per hour anyways. But the reason why his coach can not do it is probably because it is a heavy coach, so that ISL even with the horses it has, it is still carrying a lot of weight.
So a coach that is 36'or 38' with a 350hp diesel should be perfect for its weight.

All I can say is that my coach has the 3126-E Caterpillar and I have traveled all around the country with no problems as far as power goes. First towing a Honda Pilot weight of 4200 lbs and now a Honda CRV and I can not even tell they were behind my coach. I also noticed that those Cat engines it takes about fifty thousand miles before they are broken in. I have 60K miles on the engine now and my coach is running at its best. One thing that I did notice gave my coach a lot of power was changing the air filter from a Farr to a Rancor filter. Wow! a lot of difference in power.

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.

If you're within the designed specifications of the MH and the engine is well maintained and in full operational condition then it's a no brainer. If you like it go for it. All MH's slow down on certain grades. It isn't a race. Everything else your hearing is opinions about horsepower. Drop a gear if you need to, maybe two or three. Forget about the rest.

BEisler wrote:
CORRECTION . . . . the diesel we are looking at is 300 HP Cummins, not 340. Should we walk away from this?

Why?
Bill