Blue Def or at the pump?

[Gibson3798]

At a recent refueling stop I purchased a container of Blue DEF. An employee mentioned I could buy it much cheaper at the pump.

As a new diesel TV owner I need advice on whether to continue buying it as I had been or at the pump.

Thanks!

[tbrowne]

Blue DEF is about $5.00 per gallon when buying by the box. It's about $3.00 a gallon at the pump and you don't need to handle boxes or worry about spills. It's a pretty easy decision.

[21Airstream]

I usually refuel at CFN stations (or Pilot/Flying J when towing the AS) so I get my DEF at the pump (and pay for it and the fuel at the end of the month).

[BayouBiker]

$10 less and fresher. A little more hassle as pay at the pump rarely works for me at the truck stops.... DEF has a shelf life of 6-9 months at 100F. A year or more at 85, more than 2 years at 45 F.

[bweybright]

When I have looked at getting from the pump I have observed that the nozzle will not fit my DEF fill neck.....its too big.

[jaybauman]

After price, the next best thing about buying at the DEF pump is you can purchase the exact amount you need to fill up your tank.

In and of itself, the age of the DEF isn't as important as what temperatures it has been exposed to. If kept at room temperature, it's good for 2 years. At 95°F, you're looking at a 6-month shelf life. Unless you're desperate, never purchase the boxes that sit in the outside display case at your favorite fuel filling station. You'll be good with anything that's been kept indoors.

[tbrowne]

I'm pretty sure all DEF filler tubes are the same size as are all DEF hose nozzles. The DEF pumps at truck stops are generally next to but separate from the fuel pumps. Look a little closer, I think you must not have been looking at the DEF pump nozzle if you thought it was too large. If you have trouble finding the DEF pump, ask a truck driver. They will be happy to show you where to find it.

[turk123]

Originally Posted by tbrowne

I'm pretty sure all DEF filler tubes are the same size as are all DEF hose nozzles. The DEF pumps at truck stops are generally next to but separate from the fuel pumps. Look a little closer, I think you must not have been looking at the DEF pump nozzle if you thought it was too large. If you have trouble finding the DEF pump, ask a truck driver. They will be happy to show you where to find it.

I agree. Just be glad it didn't allow you to pump diesel into the DEF tank! When that diesel would hit that extremely hot catalytic burner, whoa!

[BayouBiker]

No excess oxygen in the exhaust so it's not so bad as you think. Still the filler sizes are so different, there is not much chance someone will mess up unless you fill a jug first but I'd hope people would discover it is diesel first. As you all say the def is from a different dispenser on the side of the main pump and the nozzle is usually concealed by a sliding door.

[ITSNO60]

I have a vehicle that uses about 1 gallon of DEF every 3,000 miles and it holds 3.5 gallons. (My first full tank of DEF went 12,000 miles before the 1,500 mile warning light came on)We see daily temps over 95 better than half the year with much of the summer in triple digits. With my driving lessened by both Covid and retirement I don't think I'll drive it much over 5,000 miles this year so I have been very careful to buy in small quantities with fresh dates.

Last time the light came on I waited for the warning to drop to 600 miles then I only added one gallon. (The dealership was selling bottles that were already a year old!) I have found both Blue DEF and the Wally World DEF on the shelf with dates as recent as one week. The only drawback is possible condensation but with our dry weather and the plastic tank I doubt that will be an issue, and being the solution is mostly water anyway a few drops of condensation shouldn't hurt.

Just something else to consider if your vehicle will not be driven much, or stored for a while. I think some vehicles have an easy way to drain the DEF tank but not so on my TDI.

[ExploreUT]

Originally Posted by Gibson3798

At a recent refueling stop I purchased a container of Blue DEF. An employee mentioned I could buy it much cheaper at the pump.

As a new diesel TV owner I need advice on whether to continue buying it as I had been or at the pump.

Thanks!

Have always purchased DEF from the “big boy” truck pumps and never had an issue with the quality. As noted, the turnover of the fluid is what provides the peace of mind.

Just note it is “high flow” and will fill a 5 or 8 gallon tank very quickly. Squeeze trigger slowly. DEF tanks on the semi’s are much larger given the long hauls they run.

[moosetags]

I have used DEF since the very beginning. I had a 2011 Duramax (the first year pf DEF). I also had a 2018 Duramax, and I now have a 2020 Duramax. At any fuel stop that has DEF at the pump, i always top-off my DEF tank. It was always much easier, especially when the GM filler was up under the hood.

Brian

[GOUSC]

My ‘18 GMC diesel has the DEF fill under the hood so it’s inconvenient either way. More inconvenient at the truck stops as I have to pull forward enough to pump diesel and then back up enough to reach under the hood.
I carry the blue DEF in a box in the bed of my truck and fill at my leisure at the camp site or my garage.

I usually refill before I get any warning. I carry an empty 1.5 liter wine botttle / a funnel / fill the wine bottle about 7 times and I’m done. More relaxing to me than the truck stops.

[moosetags]

What a pleasant difference now that the 2020GM fills at the fuel door. I traded the 2018 for a 2020 primarily to get the camera feature, but the DEF filler issue is just as much of a plus.

Brian

[BayouBiker]

DEF is a solution of urea and water and degrades to ammonia which is not very effective at controlling NOx. So old DEF won't harm the exhaust system, it just won't control pollution very well.

[Gibson3798]

Great advice, so thanks to all!

[GOUSC]

Originally Posted by moosetags

What a pleasant difference now that the 2020GM fills at the fuel door. I traded the 2018 for a 2020 primarily to get the camera feature, but the DEF filler issue is just as much of a plus.

Brian

I’m jealous😀

[ITSNO60]

Originally Posted by BayouBiker

DEF is a solution of urea and water and degrades to ammonia which is not very effective at controlling NOx. So old DEF won't harm the exhaust system, it just won't control pollution very well.

I do believe that old DEF can cause issues with the reductant injector, and possibly the pump, sensor and feed line due to crystallization. SCR is fairly new to me (I held out as long as I could) so I am just learning but from what I have read I came to that conclusion. These are somewhat common failures on the VW buyback cars that sat in storage for 1-2 years.

[jrwayne]

I like the pilot or flying j def. the date codes are easier to interpret. Plain date codes. No cryptic crap.

[Rgentum]

Hey, guys & gals, let's get real.

Diesel Exhaust Fluid (DEF) is an aqueous solution of urea, also known as carbamide. Urea is a remarkably simply compound; there's nothing complicated about it: two amide groups (NH2) joined by a carbonyl (C=O).

Biologically, it is the most common nitrogenous degradation product of protein metabolism and the most common compound in urine. In mammals, the liver combines two ammonia groups (NH3) with carbon dioxide (CO2) to make urea (CO(NH2)2). Chemically, it is produced synthetically and is the most common nitrogen-containing fertilizer used in agriculture. If you want to make a chemical compound containing nitrogen, urea is the usual source.

https://en.wikipedia.org/wiki/Urea

Exhaust gases contain nitrogen dioxide (NO2), which is a strong oxidant. In the atmosphere, NO2 can cause irritation of eyes, nose and throat and when inhaled can cause lung irritations and decreased lung function.

When DEF is sprayed into exhaust gases, the urea in DEF combines with NO2 to produce pure Nitrogen (N) and water (H2O), both of which are common ingredients of the air we breath, and neither of which is toxic, as is NO2.

The point I'm wanting to make is that urea is urea, and there is nothing fancy about it. Consequently, there is little if any point in wanting to buy "expensive" DEF. DEF typically comes in 2.5 gallon boxes. WalMart sells its generic DEF for approximately $8, which is $8/2.5 = $3.20/gallon, which is comparable if a little more than DEF costs "at the pump." And I find it more convenient to buy DEF in a box than at a truck stop, where I typically find the cost of diesel substantially more than at a typical service station and particularly at Costco.