−15.8%diesel per hour: a Hindustan 2021D wheel loader on a D21, 9.5 → 8.0 LVela Blue MetalA month of normal work, March 2021; signed certificate.Signed certificate →
Products · Diesel Series
Model D21
The complete diesel set for twin-tank trucks and heavy equipment — two Fuel Enhancers plus the Air Refiner for trucks, tractors and farm machinery.
Diesel2 × 100 L tanksEnhancer × 2 + Air Refiner10-year service lifeMade in Taiwan
Not sure this is your model? Use the product selector →
Specifications
Model D21 at a glance
| Model | D21 |
| Fuel type | Diesel |
| Tank capacity | Two tanks of about 100 litres each, or one tank up to 200 litres |
| Package contents | Fuel Enhancer (100 L) × 2 · Air Refiner × 1 |
| Installation | Enhancers: at refuelling, drop both into the tank. Air Refiner: inside the air filter housing, on the intake side. |
| Activation | Starts working within about 30 minutes of installation |
| Service life | 10 years, no maintenance and no refills |
| Warranty | 12 months with serial-number registration at greentech.tw |
| Best for | Twin-tank trucks, mining and excavation equipment, tractors, farm machinery and boats with tanks up to 200 L |
| Origin | Designed and manufactured in Taiwan · Taiwan and U.S. invention patents |
Where it fits
Buses, trucks, loaders and tractors
For tanks up to 200 litres: two enhancers in the tank plus an Air Refiner on the intake side. A boat with a diesel tank up to 200 L takes the same set. More complete combustion raises engine speed and output, so on a boat ask the engine maker first whether the engine has room for it.
City & coach busesDrop in at refuelling
Wheel loadersMeasured per engine hour
Tractors & harvestersFarm machineryWhat owners and fleets measured
Results vary with engine condition, load and route. Each vehicle is measured against its own original fuel use, so the percentage differs from vehicle to vehicle.
Fuel side and air side
Drop both enhancers in at refuelling; any workshop can fit the Air Refiner.
Payback calculator
Run the payback on your own fuel bill
7.2%Your assumed saving rate
India, 4 trucks, 219,793 km (2025–26)
India, 4 trucks, 219,793 km (2025–26)
Saved per month —
Payback in about —
First-year net saving —
Most documented results: 5–25% less fuel. Each vehicle is measured against its own original fuel use — the more efficient the vehicle, the bigger the denominator and the smaller the % looks, but the litres still add up. Results vary with engine condition, load and route.
🌿 Fuel is only half the story — the emissions gains (smoke down by up to 85%) carry inspection and ESG value on top.
The evidence
All test results →Don’t take our word for it: see the documents
Government tests, fleet records, customer letters and patents. Swipe, and open any card for the original document.
Fleet records · India · D51+7.2% · 219,793 kmTwo fleets, 4 heavy trucks, 9–13 months of records; payback in 2.4–3.1 monthsCase study (PDF) →
Government test · Ethiopia · D10−33.6% diesel per kmECAE, Toyota Hilux: 14.44 → 21.75 km/L, hydrocarbons −79%; 2022Official report (PDF) →
Customer test · Qatar · D51−25% diesel per kmBin Sraiya Readymix, a Mercedes truck: 2.6 → 3.5 km/L; 2023Signed letter (PDF) →
Customer letter · Saudi Arabia−10% fleet averageHizam Al-Qahtani Goods Transport: Actros MP2/3/4 and Sino trucks; 2025Signed letter (PDF) →
State bus fleet · India9 of 10 busesKSRTC: smoke down 25–85% on nine of ten buses; 2015Report (PDF) →
Fleet records · UAE−7.4% dieselIFFCO, six heavy trucks, measured by Savex; payback about one month by IFFCO’s own calculationFleet report (PDF) →
PatentsPatented in many countriesUS 11,713,737 B1 and patents in other countriesSee the patents →Installation
Enhancers at refuelling, Air Refiner at the intake
How to install
It depends on the application
The enhancer must be in direct contact with the fuel, so it always goes inside the fuel tank.
Take the fuel cap off. Can you see the fuel?
✓Yes: drop it in
Motorcycles and scooters, generators and stationary machines, some boats and other machinery: the fuel is right there, so it is simple to drop the enhancer in.
!No: many cars
The filler often has an anti-siphon valve. The tank is reached through the fuel-pump or fuel-sender service opening instead: a job for a workshop, with the fuel drained first.
- 1Fuel-pump / fuel-sender service opening (usually under the rear seat)
- 2Where the filler pipe joins the tank, underneath
- ✕Filler neck and its anti-siphon valve
Never force it down a car's filler.It can jam in the filler pipe, and the pump nozzle will then keep cutting off every time you refuel.
Not sure? Have a qualified mechanic or an authorized Greentech installer do it. Labour costs vary, so ask for a price first.
Installation guide (PDF):English · 中文
⚠Fuel is hazardous and flammable. Do not smoke near the fuel tank.
Trucks, buses and machines
D20 / D21 / D50 / D51: drop it in at refuelling, no workshop, no downtime
- Open the fuel cap at refuelling
- Drop both enhancers into the tank
- Fit the Air Refiner in the air filter housing
Tanks with internal baffles are fitted by your distributor or a trained installer.
D21 complete set: one more step for the Air Refiner
Any workshop can fit it.
Workshops & fleet service shops: become a distributor
Fleets and workshops fit Greentech every day: apply for the diesel line in your country.
Apply for the diesel line →Partnership models →Measured results
What tests show for diesel engines
7.4% across a heavy fleet
IFFCO UAE ran six heavy trucks (550 L tanks) for one month: 5–13% per vehicle, 7.4% average. IFFCO’s own calculation put payback near one month.
25–85% less smoke
KSRTC state buses in India (2015): smoke fell on nine of ten buses, by 25–85%, with no engine work.
Independent US truck tests
Letters from California Environmental Engineering on two Kenworth heavy-duty trucks, each run about 3,500 miles (2009), record better fuel economy and lower emissions.
Questions
Before you order
Does it change anything on the engine?
No. The device is passive — no chemicals, no electronics and no engine modification. It sits in the fuel tank.
How soon will I see results?
The device activates within about 30 minutes. For a reliable before-and-after comparison, record fuel consumption over two to four weeks of normal use.
My tank is larger than 200 litres — which model do I need?
Choose D50 or D51 for tanks up to 500 litres. Boat tanks above 500 L take one D50 per 500 L. Size a boat's tanks →
How do I register the warranty?
Enter the serial number from the packaging at our product registration page. Warranty runs 12 months from registration.
Does it need maintenance or replacement?
No maintenance, no refills. The service life is 10 years; after that, simply replace the unit.
How do I know my unit is genuine?
Every genuine unit has a serial number you can verify on the registration page. Units bought outside authorized channels cannot be registered.
Ready for Model D21?
Order online, or request a quote and installation for your fleet.
Where to buy the D21
Authorised distributors with a page of their own — local pricing, installation and after-sales service in their market.