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Old 01-12-2019, 11:17 AM   #1
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DP's with DEF Engines - How are they treating you?

I have a good friend who is in the final two years of pre retirement planning. And is interested in a DP to become a Snowbird.

When he asked me for input, I did my for me normal recommendation to 'Pick your budget range, and drop years to by the highest quality coach that meets your needs.' advice. I also recommended he target pre DEF engines. And he asked why? As his casual looking was at many 2014-2017 model year coaches.

And that got me to wondering if I'm a 'block head'!

Sure, quite often dramatic changes in engine smog controls have teething pains. But, if given time, usually refinements are made on later engines... I heard or 'Regen' type problems, but never having had to worry about such things, do not know if this is an ongoing problem?

So, I'd thought I'd ask for input from DP with say DEF era Diesels for input on how these engines are to live with.

-Is getting DEF a PITA?
-How often do you need to get DEF? Every fill up? Every other, or third tank - whatever? Added costs would of the actual DEF product would appear to be a drop in the bucket of the overall DP ownership - is that a good assumption?
-REGEN? Is that still occurring. And if so, do they still cause problems today?
-DEF era engines in general. Are their regular maintenance items that need to be addressed over normal non DEF diesels? Are their components that need to be replaced due to failures on a higher then noise lever frequency?
-What other pearls of wisdom should I be asking about DEF diesels, to share with my friend?

TIA, and best to all,

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Old 01-12-2019, 11:41 AM   #2
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DEF is not a big issue but certainly an issue. 5000 miles easily on a tank and it is available at all large stations at the pump. Definitely a lot more sensors and equipment which is why some take it all off but then that can be an issue in itself. I would definitely go for a coach with warranty left on the Cummins and Allison rather than buy pre def. Dealt with DEF for 9 years now on several engines and it is just one more thing to check with no major issues however idling can be so fast idle is always recommended.

You are going to get a lot of thoughts and opinions on this one.

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Old 01-12-2019, 11:49 AM   #3
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You are going to hear from all over the spectrum on this issue. There really are two separate systems. One is the diesel particulate filter or DPF that is totally separate from the second which is the diesel exhaust fluid or def injection system. The DPF is what has to regen and is usually more problematic while the def injection, while it can have problems is fairly trouble free.

DPF has been around longer than def and they have started to get most of the bugs out although there are still issues from time to time. All new semi tractors have it and def so there are lots of trucks using it and the manufacturers have been diligently trying to solve any issues because they have to deal with warranty claims.

The biggest problems arise when engines are not fully warmed up and driven short distances. This tends to clog the DPF which makes the computer force a regen to burn off the carbon in the filter. I donít think that is as much of an issue with semi trucks and farm tractors that run long hours at optimal temperatures. Most RVs with a modern diesel will most likely run long trips so should be fine. Protracted idling is also a bad idea. Start that rig up and get trucking within five minutes. Donít start and idle while you break camp, it clogs the filter.

As for def injection, the fluid needs to be kept fresh so that means sitting in a rig that doesnít get used for six months or longer in warm weather is not good. The fluid does go bad over time in warm weather. My truck uses about a gallon every 500 miles when pulling heavy loads. When I have light loads it lasts forever. You can buy it at any gas station or Walmart. I try to get it from the pump at a truck stop as it will probably be fresher and you donít have to mess around with the empty boxes.

Bottom line, donít idle new Diesel engines, run them on some long trips and let them work hard, hot exhaust is good. Use them enough that the def doesnít get old and you will be fine. There are trucks out there with lots of miles on them with the new exhaust systems doing just fine.
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Old 01-12-2019, 11:50 AM   #4
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Def can be a minor pain but not too bad. On DPs before about 16 the fill spout is on the wrong side for the def pumps. So you ether have to go in the lane backwards or use jugs.
Use wil be approx 2% of fuel on early years and 4% for later years. I use about 3 gal per fill up and I have a 13 gal tank. I can easily go coast to coast on a tank.
I buy almost all my def in jugs from WM. Just be sure and check the seal to be sur somebody didn’t return them with water inside.
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Old 01-12-2019, 11:56 AM   #5
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I would rather have an engine with DEF than one that's pre DEF.
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Old 01-12-2019, 11:59 AM   #6
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DEF system has not been an issue. The regen is done while driving and I never really know it's happening.

DEF is available most diesel stations or buy it at Walmart for $7.68 for 2.5 gal.

I carry a couple of spear containers from Walmart but usually try to fill the DEF tank while getting diesel fuel.
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Old 01-12-2019, 12:11 PM   #7
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DEF has not been an issue at all. It's easy to fill up at truck stops or from the WalMart containers. I do recommend those over the BlueDef cardboard box containers which can be a pain to use. In 19,000 miles I have used 52 gallons of DEF, which is not a major expense compared to 2700 gallons of fuel. That figures out to about one gallon of DEF for each 52 gallons of fuel. That's right at the 2% figure that Cummins says is normal consumption.
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Old 01-12-2019, 03:52 PM   #8
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I try to fill the DEF tank often so as to avoid any problems with a bad batch.
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Old 01-12-2019, 05:25 PM   #9
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Having owned and operated diesels for decades, I disagree with your advice to your friend. Dropping back in time to get pre DEF can land you in the worst engines, those with DPF but no DEF. those are the most problematic and least fuel efficient.

To get fuel efficiency close to today's engines you have to go pre EGR and DPF. And those coaches are getting old enough that reliability can be an issue depending on past maintenance or lack thereof.

DEF is nothing to fear. It costs nothing essentially, because the increased fuel economy more than pays the material cost. Power density is higher than older designs. No soot all over the toad.
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Old 01-12-2019, 06:57 PM   #10
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Thanks for the info.

The comment on the DEF had me nodding my head as it matched comment I'd remembered reading and sharing before. The new one to me, was that DEF can go bad after a period of time.

DPF. Yep to also nodding my head, and the specifics of the year and maturity of of the evolution. Good to hear that the newer generations are not as potentially problematic as the earlier ones.

Best to you all,
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Old 01-12-2019, 07:06 PM   #11
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Really like our DEF engine.

Runs great, DEF is easy to manage and the engine is tuned to the max so we get the most power out of it and still meet emission standards. No black smoke in our exhaust so the trailer stays clean.
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Old 01-12-2019, 07:57 PM   #12
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The DEF engine will run cleaner and has no more issues than any other technology improvement. My 450 ISL uses a gallon in 400 miles. I start looking at 4,000 miles for a refill. It's a non issue. The guy that advises you to avoid a DEF engine probably doesn't like an automatic transmission, power windows, or air conditioning either.
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Old 01-12-2019, 08:55 PM   #13
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The comment regarding not idling for long is interesting because Truckers often times have to let rigs idle for very long periods of time...in cold weather, it could be in excess of 12 or 24 hours, etc. I wonder how they do that without causing significant issues?
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Old 01-12-2019, 09:57 PM   #14
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Originally Posted by NCC-1701A View Post
The comment regarding not idling for long is interesting because Truckers often times have to let rigs idle for very long periods of time...in cold weather, it could be in excess of 12 or 24 hours, etc. I wonder how they do that without causing significant issues?
The owners manual for my Ď99 Cummins ISC specifically warns against idling over 3-5 minutes.

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