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Buyer Education, Oil Catch Cans

Is an Oil Catch Can Legal? Emissions Rules Explained

Tracy Lewis Performance |

This is one of the most common questions we hear, and it deserves a straight answer: catch can legality depends on where you live and how the system is plumbed into your emissions system. This isn't legal advice — it's a starting point for your own research, which you should always confirm against your state's current regulations.

Why the question comes up at all

Vehicle emissions systems, including the PCV (positive crankcase ventilation) circuit, are regulated in most of the U.S., and California (via CARB) and several states that follow CARB rules apply additional restrictions on aftermarket parts that touch the emissions system. That's why our own product listings carry this note: "The state of California and some other states with similar regulations prohibit the use of some parts on vehicle emissions systems. Please review the regulations in your state to ensure that your parts are legal for use there." That disclaimer isn't boilerplate — it's the honest answer, and it's worth taking seriously before you install anything.

Open vs. closed systems matters

Broadly, catch can setups fall into two categories: a closed-loop system routes the cleaned-up air back into the intake, keeping crankcase gases contained within the engine's emissions system the way the factory PCV setup does. An open/vented system vents crankcase gases to atmosphere instead of returning them to the intake, which is the configuration most likely to run into legal trouble in regulated states, because it bypasses the closed emissions loop entirely. The Tracy Lewis Catch Can system is engineered as a full-time-vacuum crankcase evacuation system that maintains a closed emissions loop rather than venting to atmosphere — see the technical detail on A Closer Look at the Tracy Lewis Performance Catch Can System.

What you should actually check

Before ordering or installing any crankcase ventilation product, confirm with your state's DMV or emissions-testing authority (and, if applicable, look for a CARB Executive Order number on the specific part) whether the design you're considering is legal for street use in your state. Rules vary not just state to state but sometimes by vehicle model year and emissions-test type. If you're not sure, ask before you install — not after.

Frequently Asked Questions

Are all oil catch cans illegal in California?

No — legality depends on the specific design (open vs. closed loop) and whether the part carries the required CARB approval, not on the category of product as a whole. Confirm the specific part against current CARB rules.

Does a closed-loop system avoid the legal issue entirely?

A closed-loop design that returns air to the intake rather than venting to atmosphere is generally viewed more favorably under emissions rules than an open/vented setup, but you should still confirm compliance in your specific state before installing.

Will a catch can cause me to fail an emissions test?

It can, depending on your state's test type and the specific system installed. Check your state's testing requirements and the part's documentation before your test date.

Find the catch can for your vehicle

Every Tracy Lewis catch can kit is a patented air/oil separating crankcase evacuation system, built to order for a specific engine. These are the current applications:

Not sure which you need? Browse all catch can kits, or contact us with your vehicle details and we will confirm the right fitment.

Have questions about your specific state or vehicle? Contact Tracy Lewis Performance before you order.
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