Is a Dry Sump System Street Legal?

Yes—fitting a dry sump oiling system is generally street legal, provided the installation complies with your jurisdiction’s emissions, safety, noise, and inspection rules. The system itself isn’t banned; legality turns on execution: closed crankcase ventilation, leak-free plumbing, proper tank placement, and no interference with emissions controls or on-board diagnostics.

What a Dry Sump Is—and Why It Raises Legal Questions

A dry sump replaces the conventional oil pan reservoir with an external tank and one or more scavenge/pressure pumps. The upgrade improves oil control under high g-loads, increases ground clearance, and can enhance engine reliability. Legally, however, it introduces variables that regulators and inspectors care about: crankcase ventilation routing, potential for oil leaks, pump noise, exposed belts, and whether any emissions-related hardware is altered or disabled.

What Determines Street Legality

The following checklist outlines the core areas inspectors and regulators evaluate when a vehicle has significant engine-oiling modifications like a dry sump system.

• Emissions compliance: Crankcase ventilation must remain “closed” (no vent-to-atmosphere breathers), and catalytic/evaporative systems must be retained and functional.
• No tampering with emissions controls: Do not delete or bypass PCV valves, EGR, catalytic converters, O2 sensors, or evaporative purge systems.
• OBD readiness: On OBD‑II vehicles, all monitors should set to “ready,” with no diagnostic trouble codes triggered by the modification.
• Leak-free installation: Lines, fittings, tank, and pump must not seep or drip oil; visible leaks are a common inspection failure.
• Noise levels: External pumps and drive belts must not push the vehicle over local noise limits (stationary and drive-by tests vary by region).
• Belt/drive safety: External belt drives need adequate guarding or shielding to prevent injury and meet construction-and-use rules.
• Tank placement and containment: Tanks should be outside the passenger compartment or fully sealed off by a proper firewall/bulkhead; vent lines should go to a catch can and then back to intake where required.
• Routing and protection: Oil lines must be secured away from hot or moving parts, shielded from abrasion, and protected in crash-prone areas.
• Bodywork and visibility: Bonnet/hood modifications must not create sharp edges or obstruct driver visibility; undertray changes cannot compromise safety.
• Component approvals: In some countries, parts may require certification (e.g., ABE/TÜV in Germany) or an engineer’s sign-off.
• Insurance disclosure: Many insurers require notification of significant modifications; nondisclosure can void coverage.
• Documentation: Keep invoices, installation notes, and, where applicable, engineering certificates for inspection.

Meeting these points usually satisfies the practical hurdles to keeping a dry-sumped car legal for the road, even in stricter jurisdictions.

Regional Snapshots

United States (general)

There’s no federal ban on dry sump systems. The Clean Air Act prohibits tampering with emissions controls, which includes altering or disabling PCV, evap, O2, or catalysts. Post-1960s road cars must retain closed crankcase ventilation; vent-to-atmosphere breathers can be cited as tampering. State safety/emissions inspections vary: in OBD‑II states, your car must pass readiness and have no emissions-related fault codes; in visual-inspection states, inspectors may look for intact PCV routing and absence of leaks.

California

California Air Resources Board (CARB) requires Executive Orders (EOs) for emissions-related aftermarket parts. A dry sump kit typically doesn’t need an EO if it doesn’t alter emissions controls, but if your installation changes PCV routing or adds open breathers, it can fail the visual inspection. Keep the crankcase closed-loop to the intake, preserve all emissions components, and ensure the car passes the Smog Check (OBD readiness, functional test, and visual inspection).

United Kingdom

Dry sump systems can be road legal if the vehicle passes the MOT: no significant fluid leaks, compliant emissions for the vehicle’s age, and no excessive noise. Crankcase breathers must not vent to atmosphere on most post-classic vehicles. Construction and Use Regulations can apply to exposed belt drives (guards) and to sharp edges. Declare modifications to your insurer.

European Union/Germany

Germany’s TÜV may require an individual approval (Einzelabnahme) if the modification materially affects safety or emissions. Documentation of components and professional installation helps. Expect scrutiny of belt guards, oil line routing, leaks, and whether the PCV/evap system remains closed. Other EU countries follow similar principles through their respective inspection authorities.

Australia

Compliance is under ADRs and state-based codes (e.g., VSB 14). A dry sump can be legal with engineer sign-off where required, especially if structural changes, firewall penetrations, or cabin-adjacent tanks are involved. Keep PCV closed, avoid leaks, and ensure no impact on emissions compliance. Noise tests may apply after engine modifications.

Canada

Provincial rules mirror U.S. practice: retain emissions hardware, pass OBD or tailpipe tests, and avoid leaks or exposed hazards. Some provinces have periodic inspections or require out-of-province inspections on transfer; documentation and clean installation ease approvals. Inform your insurer about the modification.

Practical Steps to Keep a Dry Sump Street Legal

The following actions help ensure your dry sump upgrade meets common roadworthiness and emissions requirements while minimizing inspection risk.

1. Plan a closed PCV layout: Route crankcase vapors to a baffled catch can and back to the intake; avoid open breathers.
2. Preserve emissions systems: Keep cats, O2 sensors, evap canister, purge valve, EGR, and associated plumbing intact.
3. Choose compliant components: Quality tanks with internal baffling, AN hose/fittings rated for oil and heat, and guarded external belt drives.
4. Mount safely: Place the tank outside the passenger cabin or behind a sealed, fire-resistant bulkhead; use proper brackets and isolation mounts.
5. Protect lines: Route away from exhaust and moving parts; add heat sleeves and abrasion guards; use P‑clips and stand-offs.
6. Control noise: Consider pump selection, drive ratio, and acoustic shielding to stay within local noise limits.
7. Verify OBD readiness: After installation, complete a drive cycle and check for stored or pending DTCs and readiness monitors.
8. Leak-check: Pressure test and inspect cold/hot; fix any weeps at fittings, tank bungs, or seals.
9. Document the build: Keep diagrams, parts receipts, and, if applicable, engineer certificates or inspection reports.
10. Notify your insurer: Provide details and photos to ensure coverage remains valid.

Following these steps typically keeps the modification within legal boundaries and reduces the chance of inspection failures or insurance disputes.

Common Myths

Dry sumps attract myths that can lead to costly mistakes. Here’s what owners should know.

• “Dry sumps are illegal on the street.” False: legality depends on emissions, safety, and noise compliance, not the oiling system type.
• “You need a CARB EO for any dry sump.” Not usually: you need an EO only if the kit alters or affects emissions controls; keep PCV closed and emissions intact.
• “Open breathers are fine if the car passes tailpipe.” Incorrect: crankcase ventilation is regulated; vent-to-atmosphere can fail visual inspections and constitute tampering.
• “Front-mounted tanks are always illegal.” Not inherently; they must be securely mounted, outside the cabin or behind a proper bulkhead, and meet safety rules.
• “Any inspection will fail an external pump.” Not if the installation is quiet, guarded, leak-free, and doesn’t interfere with other systems.

Understanding what inspectors actually check helps separate fact from fiction and guides a compliant installation.

Summary

A dry sump system can be street legal in most regions when installed thoughtfully: keep crankcase ventilation closed, retain all emissions hardware, contain noise, guard external drives, mount and shield components safely, and avoid leaks. There’s no blanket prohibition on dry sumps; legality hinges on meeting the same standards any road car must satisfy. If in doubt, consult local regulations, an engineer/inspector, and your insurer before finalizing the build.

What vehicles use a dry sump?

Dry sump lubrication is common on larger diesel engines such as those used in ships, as well as gasoline engines used in racing cars, aerobatic aircraft, high-performance personal watercraft, and motorcycles.

Are all 911 dry sumps?

All Porsche 911 cars have always had them. Pretty sure most Boxster/Caymans do now as well, but initial models didn’t.

What are the disadvantages of a dry sump system?

Dry sump systems require additional components, such as an external oil pump, oil lines, and a separate oil tank. This can make installation and maintenance more challenging, as well as increase the overall cost of the system.

What is the alternative to a dry sump?

Dry Sump Alternatives
If a dry sump system doesn’t fit a racer’s budget, there are lower-cost alternatives. “One option is an external wet sump pump, which is a belt-driven, single-stage pump,” said Hall.