DEF usage at idle
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DEF usage at idle
We were in Sweetwater, TX Friday thru Sunday evening at a local motel and caught on the artic blast. Lows near 0 degrees and black ice so we stayed put. We picked up our 40’ fifth wheel there Friday. We had power outages in the motel, ended up idling the 2020 -F-350 for about two hours, 30 minutes at a time over the three days. We were topped off with DEF fluid on Friday. When we hit the road Monday, we had only a couple gallons DEF fluid remaining. Received the Low DEF notice on instrument cluster...500 miles remaining. Is this normal usage at idle in these temps? We used a fuel additive at appropriate ratio to prevent gelling...there were three trucks that wouldn’t start...all forgot to treat the fuel. I expected to add DEF about every 4000 miles.
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From: BC Canada
Tank might be frozen, or overfilled, there is a heater in it, so after a lot sustained driving, it should correct itself, I would be wary of adding too much. I’ve never seen it burn any DEF just idling. Do you have any codes, engine warning lights, any messages in the message centre or warning lights on?
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No codes or engine warning lights. The gauge showed less than quarter tank and got the notice that DEF low, 500 miles remain. I pumped almost three gallons DEF at a truck stop and gauge shows full...still getting the notice for low DEF fluid on the center dash.
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From: BC Canada
Gauge takes a long while to respond when you fill. Especially when cold. If it was at 1/4 full, should have taken about 5.5 gallons. It’s good you didn’t overfill. If you check your dash, there is a gauge, and a DEF OK screen. Check both. If you have no codes, you have no driving issues, just drive. DEF freezes, there is a heater in the tank, which will thaw it. When you shut the truck off, when it’s cold, it pumps the DEF out of the lines back to the tank to keep it heated. If it starts giving messages, I would take to a dealer for assessment, if it still goes fine, tows fine, runs properly, I would just drive and not worry. By the time you get home, the DEF will get up to speed. I find towing is the most DEF consumption. Never had it use a lot idling but then, I have never idled that long. Update us when home safe.
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What temp do you like to see on the gauge before towing...when starting cold at 5 degrees for instance. If I’m consuming that much DEF at idle in cold weather, I want to warm up minimum time but reach a healthy temp for the 6.7 to perform.
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From: BC Canada
I like to wait until it’s over 100 f before going on it to hard, idling out of town, hitching up, getting out of the camp ground, I never hit the fuel hard. But once it’s got 100 f in the coolant, trans is coming up, I don’t feel bad stomping on it to get out on the highway, get up to speed.
with how cold it is there, and your longer idle times, I think your truck must have been idling up quite high for that much DEF. how much fuel did you burn in 2 1/2 hours of hi idle?
with how cold it is there, and your longer idle times, I think your truck must have been idling up quite high for that much DEF. how much fuel did you burn in 2 1/2 hours of hi idle?
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I’m estimating the idle time but not far off one way or the other. I burned 10.5 gallons but that includes towing 16K, 40’ er for 85 miles. I’m curious if the fuel treatment had anything to do with burning that much DEF.
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Postmaster
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From: BC Canada
Fuel treatment doesn’t have anything to do with the DEF. DEF is burned under the right temperature conditions when there is NOx in the exhaust. The DEF is to reduce this NOx. I would think that heavy new trailer (40 feet, 15,000 lbs?) and 85 miles towing hard also burned a fair bit of DEF. I see the most DEF consumption towing and hot weather. The fuel treatment is good, to prevent gelling and add cetane, which burns cleaner, makes more power. Adding it to winter fuel is good, prevent the gelling as winter fuel is generally less energy, so your fuel mileage goes down a bit.
last oil change, no towing, 5000 miles, 1/2 tank DEF, previous oil change 5500 miles, half towing, 10 gallons DEF, I tow half the weight you do, sometimes truck is heavier but mostly half gross combined your at. I have had towing trips where I had almost a full tank DEF by end of trip or before getting warnings to add DEF.
last oil change, no towing, 5000 miles, 1/2 tank DEF, previous oil change 5500 miles, half towing, 10 gallons DEF, I tow half the weight you do, sometimes truck is heavier but mostly half gross combined your at. I have had towing trips where I had almost a full tank DEF by end of trip or before getting warnings to add DEF.
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Two reasons. Both truck and fifth wheel were new to us. We spent time orienting ourselves to features/accessories on both. Five degrees outside and motel we we’re staying on list power for over 24 hours so we used truck to warm up ourselves and pets...good question though.
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I hardly tow, but I idle *a lot*, and my truck guzzles DEF. I'm at 9,000 miles and just added the seventh 2.5-gallon jug (17.5 gallons added, for the math-challenged). I have a kid and dog with me every day, and sometimes the truck will idle for an hour or two while I'm wrangling them, or we get sidetracked and forget we're going somewhere, or just change our minds.
So, yeah, idling DEFinitely* causes a rate of consumption increase.
*See what I did there? That's a pun. I'm a funny guy. Great at parties, too.
So, yeah, idling DEFinitely* causes a rate of consumption increase.
*See what I did there? That's a pun. I'm a funny guy. Great at parties, too.
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From: Kaysville Utah
I agree with Mike, It's not the idle that consumed the DEF. NOx is produced at high combustion temps. ie basically when your turbo is adding boost.
Idle does not produce high combustion temps. In fact idling will barely get up to 300° EGT's
Idle does not produce high combustion temps. In fact idling will barely get up to 300° EGT's
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you can also get higher than normal NOX values is your diesel supplier mixes in BIO fuel into the diesel...a lot of services stations will sell B2.5 thru B5. The BioDiesel blend has less BTU , burns cleaner in terms of soot, but produces more NOX levels
the actual DEF gauge is very iritic. yesterday mine fluctuated between 80% full to full for most of the day. at mid day for example, parked my truck and it was 80%. came back 20 minutes later and it was 100%.
Mixed theories on keeping it full or not...some say if you top off, the tank could crack when cold....others say you have to keep it full to cover the heating elements.
so you have to plan your usage and refill so that its almost full during cold months to get the most out of the heating element with out filling it too much that expansion cant occur and tank cracks.
someone needs to come up with some winter def that can stay liquid at cold temps.
the actual DEF gauge is very iritic. yesterday mine fluctuated between 80% full to full for most of the day. at mid day for example, parked my truck and it was 80%. came back 20 minutes later and it was 100%.
Mixed theories on keeping it full or not...some say if you top off, the tank could crack when cold....others say you have to keep it full to cover the heating elements.
so you have to plan your usage and refill so that its almost full during cold months to get the most out of the heating element with out filling it too much that expansion cant occur and tank cracks.
someone needs to come up with some winter def that can stay liquid at cold temps.
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