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Old 12-04-2015, 07:26 AM   #1
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Requirement for DEF

In my quest to get educated about diesel pushers I've been told that a coach made prior to the DEF requirement would be best.
What year did the requirement for DEF start?
Also, any other thoughts from those who have a newer coach requiring DEF would be helpful. I have a 2015 F-350 that requires DEF. It's not a huge issue but it definitely uses more when under a load.

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Old 12-04-2015, 08:11 AM   #2
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Five years ago we bought an '09 coach that did not use DEF. Now we have a coach that requires DEF. No difference other than I have to buy DEF. I think it started in 2010.

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Old 12-04-2015, 08:48 AM   #3
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If you do a site search on DEF you'll find dozens of threads on the subject, many of the "dooms day" variety were started before there was any real world experience with it.

Any engine/chassis manufactured after January 1, 2010, had to meet the new EPA standards, thus 99% of coaches built after that date will require DEF. Some manufacturers had a back log of pre 2010 chassis on hand when they started building their 2010 model year rigs and there was one engine manufacturer that tried to meet the standards without DEF (which was largely unsuccessful), so there are a few rigs out there titled as a 2010 that will not use DEF.

We never owned a pre-DEF coach so I have no real frame of reference, but I can tell you that DEF has not been anywhere near the joy killer some would have you believe. Our coach came with the Cummins 450 hp ISL and I'm using just under 2% DEF to fuel. In other words, for every 100 gallons of fuel I burn I'll go through a couple of gallons of DEF. If you buy DEF by the jug (rather than "bulk", at the truck stop) you will likely pick it up in 2.5 gallon jugs. Right now you can buy that for just under $8 at Walmart. For us that will be good for over 1000 miles of travel. We were told by a chassis rep that they try to size the onboard DEF tank to last approximately 4 tanks of fuel. Theoretically we could travel 4000 miles before we'd run out of DEF. In our coach the DEF tank will take another 2.5 gallons not long after the DEF level gauge drops to 3/4s full. At that time I'll top it off with the container I always carry with me and the next time I'm at Walmart I'll buy a replacement.

I can tell you that the only thing coming out of our tailpipe is moist heat - zero smell. I only wish our generator and Aqua Hot burned that cleanly.
Jay & Peggy Monroe with Dolly
Can't take it with you - don't plan on leaving any behind
2016 Newmar London Aire 4553, Spartan chassis
Wrangler Unlimited toad
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Old 12-04-2015, 08:54 AM   #4
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New to me 2011 Phaeton that needs to be fed DEF. So far, not a biggie. Just buy it at Walmart and pour it in.

Would be much better if the DEF tank was not on the wrong side for bulk filling at truck stop pumps. Would be a near total none issue then.
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
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Old 12-04-2015, 09:01 AM   #5
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If you're concerned about such things, its not pre-DEF you want, but pre-DPF. DPF have been required since 2007. Of course, a 2007 or 2008 motorhome could be on a 2006 chassis. Of course, now that's becoming an older motorhome that can all sorts of other issues.
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Old 12-04-2015, 09:27 AM   #6
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Exclamation DEF.

The only issue with the DEF is the effect of heat that will cause the DEF to deteriorate, anything above 85 degrees shortens the life span of the DEF. It also has a born on date that should be checked just as tires do. Unless you are an over the road truck we will all be better off with the Wally World containers.
I filled the tank on my 3500 after first running the truck until the light came on for the DEF. I live in the South and will not fill the tank again because of the heat we have in summer.

Food for thought:
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Old 12-04-2015, 09:28 AM   #7
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My first two DP's were pre DEF and DPF and I did like them better. Either diesel (1995 Cummins ISB and 2002 CAT C12)left me with nothing but confidence and reliability. This coach is 4 months old and the exhaust treatment system has "annoyed" me twice. First was on the first trip when DEF fluid dropped and I scrambled to buy the stuff. Then last month while traveling a engine warning light came on. I called FL and they said it's a malfunction with the exhaust treatment I can continue but will need to go to FL service to have it looked at. Wonderful. Neither was huge but it's two things I didn't have to deal with before the wonderful change in requirements.
Bill & Kelli 2015 Dutch Star 4366
2002 Safari Zanzibar 3906
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Old 12-04-2015, 10:45 AM   #8
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On Jan 1 2007 the updated EPA requirements made DPF necessary and diesel fuel economy took a hit. Then on Jan 1, 2010, further updated EPA regs required the addition of a catalytic exhaust treatment and the use of DEF to feed it. The good news is that the DEF system helped restore some of the fuel economy that was lost in 2007. Every new subsystem adds complexity and possible failure points, however, and new tech has some potential for unexpected problems in the early days. DEF systems are pretty solid now, though.

So, for best fuel economy and a simpler engine, you want an engine built before 1/1/2007. However, the newer ones pollute less, with substantially reduced NOx emissions. You make the call on the tradeoffs.
Gary Brinck
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Old 12-04-2015, 10:47 AM   #9
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Thanks folks.
I was hoping it was a non-issue like it's been on my truck.
I used the bulk DEF pumps at a couple of truck stops during the last trip and it only added about $5 to $7 to the cost of the fuel
Our local Walmart sells the 2 1/2 gallon DEF for $12.50 + tax. The truck stops were about $2,50 per gallon on the trip.
It's definitely more convenient to top off the DEF during fueling but only if the fill point is on the same side as the fuel. The truck stops have sattelite fuel nozzels but not for the DEF.
Your responses give me some room to look for a newer model coach if one comes available.
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Old 12-04-2015, 10:51 AM   #10
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Not sure who told you a pre-def engine is better but I seriously question that advice. The newer engines run cleaner and with newer electronics get slightly better milge for the same HP. (Per Cummins)
I never let my def get below 3/4, same for fuel tank, which means I refill def about every fifth or sixth fuel stop.
I'm lucky that my def tank is on DS so it's easy to use the bulk despenser at truck stops.
Paul, Kathy, and Tux a 4 month Mini Schnauzer
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"When the time comes to look back, make sure you'll like what you see"
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Old 12-04-2015, 10:57 AM   #11
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Anyone who told you that a "pre DEF" coach was better, probably never owned one with DEF or had a "pre DEF" coach to sell.

The DEF coaches not only run cleaner, but get better mileage as well.

The reason that they get better mileage is because the engines don't have to be built as "tight" so that they can pass emissions.
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Old 12-04-2015, 11:18 AM   #12
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Requirement for DEF

Agree with the comments above. DEF engines run cleaner and get much better fuel mileage. I can get 11 mpg in a 40' DP with a 5.9L 340 HP DEF Cummins; a Non-DEF engine pushing the same size would typically get 5-7 mpg. I'll take the DEF engine!

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Old 12-04-2015, 11:32 AM   #13
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My 2 cents...I operated a fleet of three tractors pulling dry vans in California from 1972 to 2012. The older Cummins and then Cats in the early 90's were easy to live with relative to the new smogged engines. I bought one of the last smogged Cats with twin turbos and a mess of lines, valves, relays to deal with. No thanks. On a personal experience my old 5.9 Cummins could get 20 mpg+ freeway empty and towing 11,000# I could get 14 to 15 mpg at 65 on flat ground. My 6.7 gets 8 to 10 mpg average on the same road with the same weight. The maintainence cost I incurred on the smogged KW with the Cat was siginificantly higher than the older engines. Yes the new engines do run clean but the consumer will shoulder the cost. The newer smogged engines do run hotter that results in a cleaner more efficient fuel burn. The smogged Cat does get better fuel mileage but most is offset by maintainence costs. Yes in '07 the smogged engines were introduced and have a regeneration sequence of pumping raw diesel into the exhaust to clean the DPF. Then exhaust fluid was introduced and as I understand the engines used both fluid and diesel to clean the DPF. Now recently as I understand the newer engines use only the fluid to clean the DPF. Realize that these new engines have a higher cost to maintain. You have the crank case gases recirculating and the DPF cleaning the exhaust. Good luck.
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Old 12-04-2015, 11:48 AM   #14
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Originally Posted by ernieh View Post
Anyone who told you that a "pre DEF" coach was better, probably never owned one with DEF or had a "pre DEF" coach to sell.

The DEF coaches not only run cleaner, but get better mileage as well.

The reason that they get better mileage is because the engines don't have to be built as "tight" so that they can pass emissions.
Depends on what you mean by pre-DEF. 2010 and later models are in better than the 2007-2009 models, but a pre-2006 doesn't meet emissions and doesn't have to exhale through a restrictive DPF.

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