Neil from Messick's here to dispel a myth today. Maybe an urban legend. Who knows what you want to call it. Tractors have changed a lot over the last couple of decades. As emissions tiers have rolled out, the technology that powers your engines has changed radically over the last 25 years or so. Today we're going to talk about a fuel consumption concern that I sometimes have heard in regards to the diesel particulate filter, the DPF, that sits on the outside of all modern engines from 26 horsepower and up.
This soot capture device sits on the outside of your engine, captures soot, and periodically has to go through a regen cycle. A regen cycle that is powered by diesel fuel. Today, we're going to go through and take a look at the amount of diesel fuel that's used in that regen cycle and how it may be affecting your tractor's fuel economy.
Why can an engine use more fuel during regen and where does this concern come from? Sitting on the top of the engine is your big silver canister, your easy bake oven, the diesel particulate filter. That thing is going to plug up with the soot coming out of your engine then periodically needs to go through a burn process to burn that soot off. Now, in order to burn it needs to get hot and the way that it gets hot is with diesel fuel.
What your engine is doing is on the exhaust stroke of the engine where normally it would be pushing just the exhaust out of the muffler and down through the DPF, your fuel injectors are actually running. It is injecting fuel into your engine on the exhaust stroke, not burning that fuel, pushing it up out of the valves and down in through the DPF where it's going to get caught in the DPF in the mesh elements that are inside of that and burn creating all of the heat that is needed in order to purge the soot out of the DPF and clean it out.
The concern here that we're testing today is just how much fuel is being pushed out that exhaust stroke. Not doing any work, not operating the machine, not spinning the cylinders, not moving dirt and doing work. It is simply being blown out through the exhaust to generate that needed heat. How wasteful must this be?
We have equipped this Kubota M5111 with an external fuel tank to be able to measure the amount of fuel that this tractor uses.
For our first test, we filled this up to a measured amount and then forced the tractor into a parked regen. It was not ready to regen, but by forcing the tractor into the parked regen, we could start the burn process, the easy bake oven there on top of that engine to go and burn the soot out, let that process run. Now, it only ran for 13 minutes because it didn't really need one at the time, there wasn't a whole lot of soot in there, but we did that, measured the fuel amount down here at the bottom of our canister.
We then decided to repeat that same test now but with the tractor at the same engine RPM. We raised the RPMs up to 1,650 where that regen process was having the RPM set in order to take place to generate the heat that's required for the process, ran for the same 13 minutes, measured our fuel consumption, and our result made no sense at all. We couldn't find one.
We couldn't appear to find any fuel. In fact, within the margin of error here, we actually burned less fuel during this one, so we got opposite result than we were looking for. Now we had to retool things and come up with a different way in order to test this. Clearly, our methodology was probably a little bit flawed and our testing device is not accurate enough to be able to drill down to the amount of fuel that was being used.
We went and pulled out a dealership technician laptop. Now, these laptops have a lot of diagnostic ability. They do some fuel readings and they give us some real-time charts of how much fuel is being used. Now, it wasn't as easy as just sitting down and looking at the technician laptop because those charts tend to bounce back and forth quite a lot. Even when the tractor's sitting here at a constant RPM, it's not like you get a nice consistent fuel usage. It tends to ebb and flow.
We took the data here out of the dealership technician laptop, export it to the Excel, and then came up with some value. We repeated exactly the same two tests that we did. This time a 10-minute interval. We burned for less time because we had even less soot inside the DPF, and then a 10-minute interval with no burn going on but at the same engine RPMs. For our results. Now, when the tractor is sitting here and it's not burning, it's not in regen, it's using 3.2444 liters per hour of fuel.
If we convert that to gallons per hour, that's 0.86. When we go and check it burning, here now we're into the DPF burn. We're letting that fuel go through the engine, out the exhaust to create the heat inside of our easy bake oven. We now are burning 3.2999 gallons per hour of fuel or 0.87 gallons. It gives us our difference of 0.01 gallons per hour of fuel, so the fuel usage of this tractor during that regen process, the amount of fuel that's being thrown away down the exhaust, is a measly 0.01 gallons per hour.
As we've been doing this fuel testing, we continue to collect data points. Another thing that I think is really interesting here is what the fuel usage numbers themselves are. This 0.86, 0.87 gallons per hour. This is a 110-horsepower tractor at the engine. It is a good size machine. We're sitting here with the revs revvede the whole way up with the engine screaming during this regen process, but yet we're only using about eight-tenths a gallon an hour of fuel. That's it. Which is interesting.
We've gone through and we've shown time and time again throughout this testing on different models that the fuel usage of your tractor has very little to do on what you set that throttle to and a whole lot more to do with the work that's happening out the back end of your tractor with the actual load that is put on that engine is what drives your fuel usage.
If you have further questions about this, if there's other things that we can test here in regards to emissions and fuel economy, let us know down in the comments.
There's your answer. That is the amount of added fuel usage out of that DPF, and over even the entire lifetime of this machine, that's unlikely to add up to even more than a dollar's worth of diesel fuel. It's virtually an undetectable amount even here during my little bit of testing.
I love making videos on emissions topics. Even with these systems being around for 15-odd years now, there's still so much misunderstanding about this stuff and its mechanics and how it works. I love dispelling some of those myths. These modern Tier 4 engines are more fuel efficient than some of the ones from the years gone by. If you compare them to their Tier 2 and Tier 3 variants, machines have gotten more fuel efficient over the years and you're not, say, pissing a lot of that fuel away into that DPF.
If you're shopping for a piece of equipment and we can help, we've got parts or service needs for a machine you've already got. Give us a call here at Messick's. We're available at 800-222-3373 or online at messicks.com.
