We Test the Toyota Prius Upgrade You Never Ever Want to Use

It’s the rough idle no Toyota Prius owner ever wants to hear. When my neighbor heard a “loud, throaty sound” from his otherwise quiet Prius one morning, he knew the catalytic converter had been stolen. Installing a new version of that smog-cleaning part can cost thousands of dollars, and the theft reminded us we might be vulnerable, too: We’re driving a 2024 Toyota Prius Prime in the unofficial Prius capital of the world, Los Angeles.

See All 25 Photos25

Maybe we should invest in some protection?

We set out to discover how much a catalytic converter shield costs to install and how it changes the car’s performance. Would we sense rattles from the catalytic converter shield we chose, the Cat Shield by Millercat? Would the service techs at our Toyota dealership like the new component's design? OK, that wasn’t on our list, but we got an answer on that, too.

Now that we’ve driven our 2024 Prius plug-in hybrid for six months with the Cat Shield installed, here’s what we’ve found.

See All 25 Photos25

How Much Does a Catalytic Converter Shield Cost?

Toyota tells us that more Prius cars are sold in California than any other state (New York, Florida, and Texas follow). Millercat isn’t the only catalytic converter shield purveyor around, but it is the only one directly in Toyota’s configurator in the Accessories section under Protection. Millercat offers two options: aluminum or stainless steel.

The aluminum option is the cheaper of the two, and Millercat CEO John Lee describes it as a great visual deterrent. The stainless-steel version costs more but should provide more protection by making a theft more time-consuming and noisier. On our 2024 Toyota Prius Prime, the standard prices range from $150 for aluminum and $200 for stainless steel. Those prices will shift based on which model you have—the Cat Shield for a 2024 Tacoma ranges from $250 to $320.

See All 25 Photos25

Installation

No drilling is required for installation; either do it yourself if you have access to a car jack or do what most customers do: take it to a dealer. That’s what we did. When it came time to service our Prius Prime, we headed to Toyota of Hollywood, incidentally the first Toyota dealership to open in the country well over half a century ago. Our regular service was free thanks to ToyotaCare, which includes regular service visits for two years or 25,000 miles.

Our Prius had its catalytic converter shield installed in just under an hour, and the technician told us the new Cat Shield for the 2023-and-newer Prius is way easier to install than the older product for older Prius cars. After a multi-point inspection, tire pressure check, and tire rotation, I was on my way. With my 15-percent-off coupon, one hour of labor cost $194.65 for the Cat Shield installation.

Prius Performance With the Cat Shield

After six months and about 8,000 miles of driving, we haven’t noticed any difference in performance. No change in quietness, no rattles, no discernable shift in acceleration or heat. Our catalytic converter, most important, is still attached to our car after about 13,000 miles. If anything changes during our time with the car, we’ll let you know.

See All 25 Photos25

Total Cost of a Catalytic Converter Shield

Our Cat Shield by Millercat was sent to us for testing, but if we’d paid for it, we’d be looking at $200 plus tax, unless it’s on sale. Shipping would have been free to where we are in Los Angeles. Add in the installation cost, and the total price would have been about $413.

So, is it worth it? Are you the type of person to buy the insurance when you travel? Then probably yes. Have you placed a shipping pallet underneath your older Prius to discourage theft, as someone has near me? Then definitely yes.

Our recommendation? The value of the Cat Shield is highest if you don’t have a locked garage to park in. If you’re the protective type or you’ve already been a victim of this crime, if you consider one at all, commit to the extra protection by investing in the stainless-steel option.

See All 25 Photos25

For More on Our Long-Term 2024 Toyota Prius Prime XSE:

• We're Testing a 2024 Toyota Prius Prime XSE for a Year: Will We Get EV Envy?

• That's Progress: How the 2024 Toyota Prius Prime Compares to the Original 2001 Prius

• 2024 Toyota Prius Prime Test-Drive Checklist: 5 Things to Consider
• 2024 Toyota Prius Prime Plug-In Hybrid at $43,000: Worth It?
• 2024 Toyota RAV4 Prime vs. Prius Prime: Which Plug-In Hybrid Is the Better Toyota?
• Does the Toyota Prius Really Look That Great? We Asked Tomorrow’s Car Designers
• Plug-in Hybrids? Just Say Hell, Yes (If You’re This Type of Person)