Overview
Black diesel is cleaned, dried, and solvent-blended waste motor oil (WMO) used as an alternative diesel fuel. US Filtermaxx has refined this process since 2004 with over 4,000 hours of engine run-time. Most engines require no major modifications.
Step 1 — Settle the Oil
Store collected WMO in a tank with a bottom drain for several weeks. Layers stratify:
| Layer (Bottom to Top) | Contents | Action |
|---|---|---|
| Bottom | Dirt, heavy debris | Drain and discard |
| Lower-middle | Water and antifreeze | Drain and discard |
| Middle | Mayonnaise emulsion | Drain and discard |
| Top | Clean usable black oil | Retain for centrifuging |
Never use oil containing paint. Paint residue cannot be centrifuged out and will damage injection equipment.
Step 2 — Centrifuge the Oil
A centrifuge is required — fabric filters cannot remove the sub-micron contaminants that damage fuel injectors. Feed hot oil (160–220°F) slowly through the centrifuge.
Centrifuge Parameters
- Feed rate: ~1 quart per minute or slower
- Oil temperature: 160–220°F
- G-force: 2,400–10,000 G depending on model
- US Filtermaxx centrifuges are force-ventilated to exhaust water vapor
Step 3 — Blend with Solvent
| Solvent Addition | With Diesel — Viscosity Reduction | With Gasoline — Viscosity Reduction |
|---|---|---|
| 10% | ~33% reduction (to ~67% of original) | ~50% reduction |
| 20% | ~55% reduction (to ~45%) | ~75% reduction ✓ Recommended |
| 30% | ~70% reduction (to ~30%) | ~87% reduction (gasoline max) |
| 40% | ~80% reduction | Not recommended |
| 50% | ~87% reduction | Not recommended |
An 80/20 WMO-to-gasoline blend is the standard starting point. Mix vigorously — at least 20 minutes per 100 gallons. Rest overnight to let air bubbles escape.
Do not exceed 30% gasoline. Store blended fuel away from all ignition sources.
Step 4 — Final Filtration
Filter through a 2–10 micron filter at the point of dispensing. With proper process execution, fuel filters typically last 2+ years and 30,000+ miles.
Compatible Engines
Recommended Engine Platforms
- Cummins diesel engines
- Ford 6.9L and 7.3L IDI diesels
- Chevrolet 6.2L diesel
- Volkswagen, Mercedes-Benz, and Jeep diesels
- Any IDI (indirect injection) engine
Note: Late-model diesels with advanced emissions controls have no established track record with blended waste oil. Consult local regulations for fuel blending rules and applicable taxes.