Device to add an additive to a truck diesel engine

I think that is going to be difficult because you cannot blindly inject the additive as a function of time. It must be injected according to the fuel flow (assuming your trucks don't recirculate fuel back to the fuel tank as is done in modern cars. That is an expensive system and probably prone to failure. Truly the least expensive way to do this would be to treat the fuel in the fuel truck where you have better control. You didn't say how precisely you need to maintain the 1:2000 ratio

Seems to me that both adding additive at the source (at the tank farm as is done with injector cleaners in the U.S) and metering at the fuel intake line are both unfeasible. For the former, you probably could not control the process, or would need alternative sources to adhere to the same standards--assuming there was a standard or could be a standard. For the latter, as mentioned, it would have to be so complex (and so difficult to have ready replacements) as to be of questionable accuracy and reliability--and its maintainability would be questionable, reducing the availability of your truck over the long haul. Seems to me--and the size of your truck makes this imminently feasible--that the simplest solution is to do the mixing in an auxiliary onboard fuel tank, the tank from which the engine actually draws fuel. In conjuction with the auxiliary tank could be mounted an additive reservoir tank. When the fuel in the auxiliary tank is about to run out (or even when it does run out--assuming you have some fuel remaining in the carburetor bowl) the auxiliary tank would make a "request" to be refilled from the main fuel tanks--the ones that were filled at the fueling station. When this happened, the reserve tank would release its measured "dosage" of additive into the aux. tank (or into the fuel transfer pipe going to the aux. tank to promote rapid mixing). The controls for actuating release of the next fuel batch (and additive batch) into the aux. tank could be effectuated by the fuel guage sender within the aux tank. The "recharging" of the aux. tank could be either automatic, or manually controlled following an alert signal to the truck operator, or either/both.

Interesting conceptual problem. I remember that the automotive industry has dealt wtih this before oil injection for two-stroke engines. This would likely already have been engineered and tested. Saab and some motorcycle manufacturers have these systems. Also, depending on the mixing qulaities of the fuel and additive, there may be a tendency for the additive to stratify in the bulk storage tank, resulting in unevenly dispensed mixtures.

Stratification? Possibly. That's another reason, it would seem, that onboard mixing would be best. Although I would suspect that fuels are drawn from bulk storage in such a way that stratified layers are remixed. As to stratification in the vehicle's tank--say, when it was parked and not moving/vibrating--it would be hard to see how stratification would present a problem. For one, if the vehicle had been parked, stratification would not have much affect on fuel already in the carb. If fuel injection, the same would hold true for fuel in the rail; and fuel recirculation would tend to quickly remix the fuel tank. Finally, remembering that the inquirer's mixture was to be 1000:1--far "sparser" than, say, the 50:1 (and less) mix ratio for two-stroke-per-cycle engines--it would be difficult to imagine how any incidental variability would have a measurable or noticeable impact on engine performance. Could be wrong but that's my sense of it.

I have an associate that does metering pumps and I do controls. I believe that if you could arrange the fuel flow such that the additive injection port were down line from the point at which the raw fuel is recycled to the tank that this can be done. If you would require a system to be designed I believe this is something we could do.

That said, I don't disagree with the above comment that it would be an much more expensive solution than pre-mixing the additive at a different location!

Your best bet as mentioned in others posts is to mix the fuel to the correct ratio before you put it in the trucks tank. This way you can treat a large batch and will avoid any sort of expensive additional equipment. Maybe the better question is why can't you just mix it before you pump it in the truck? I'm assuming you have some sort of diesel tank on site, no? If do have to mix it in the trucks tank one fill at a time – I'd use a syringe to meter out the proper amount for your 1:2000 ratio on each fill. Easy to meter & no mess to deal with.

I have an engine that burns about 8 gallons an hour under load, that may or may not be typical for a mining truck, but for argument sake let us say that it burns 10 times that amount or 80 gallons an hour. At a ratio of 1:2000 the additive flowrate would be about 2.5 ml per minute. That is an awfully small pump, compared to the fuel flowrate. I think I would reccommend mixing at the bulk storage site, it would be easier to mix 1 gallon in 2000 gallon tank of diesel and fill the trucks from a single location, than to have a bunch of truck with these tiny metering pumps, reservoirs and tubes and fittings running all over the place. Keep it simple, one pump, one tank, one mixing place.