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Car Talk Helps Bust the Myth That Soy Is Why Rodents Are Eating Your Car’s Wires

A rodent has eaten your car’s wiring. Now you find with a 30-second internet search that the cause is soy. Look harder for the real facts.
Image by John Goreham

When my neighbor first had me over to show me his vintage 1908 Buick Roadster we were in for a surprise. When he lifted the car cover off of it mice scurried away revealing a pile of stuffing from the car’s seats and a bunch of half-eaten wiring. Jim told me this is something he had struggled with since his family owned the car. No, it wasn’t soy-based wiring that attracted the mice to chomp on Jim’s 113-year-old car. Rather it was instinct and the need to keep a chewing habit satisfied.

The myth that car wiring is being eaten by mice and other rodents due to the industry’s ubiquitous use of modern wiring that contains soy has been discounted by experts who have been in the auto industry the longest. In his most recent Car Talk column, master mechanic Ray Magliozzi* (pronounced Mal-Yotsee) says there is no evidence linking the covering formulation of wires today and the rodent damage that has been happening since the dawn of the automobile.

Commenting on the idea that it is a new additive that is causing today’s rodent damage, Ray says, “...while this is a plausible-sounding theory and may prove to be correct someday, we haven't seen any evidence we can cite that blames soy content in wires.” Ray goes on to say, “We know they like warm places to make nests, like engine compartments. And we know they like to gnaw on stuff, because their teeth are always growing.”

While you may disagree with one of America’s most respected and best-known mechanics, what is not up for debate is that one specific brand is using a specific wiring type that is the cause of your vehicle’s damage. Simply search “Rodent damage in cars” to see the many brands that are affected. By our estimation, it is every brand. From every part of the world. "One brand’s novel soy wire" is not the cause of rodent damage in cars. Furthermore, rodents eat more than just elastomeric wire coverings in cars, They eat hard plastic components such as windshield washer tubing, induction plumbing, and even hoses.

A class-action lawsuit against Toyota related to rodent damage was dismissed by a judge due to lack of evidence.

Need more proof? The folks that produce soy commissioned a formal scientific study. Hey, why would they lie? In the study, researchers exposed elastomers and plastics with and without soy-based ingredients to mice. The mice chomped on both types quite happily. Sometimes science isn’t all that difficult to conduct.

Consumer Reports calls rodent damage to cars an "age-old problem." The group also spoke to the pest control company Terminix, which also says that soy has no role in rodent wire gnawing.

Image by John Goreham

If your car’s wires have been eaten by rodents contact your insurance provider. Most auto policies with comprehensive coverage do cover damage of this type, less your deductible of course. If you’d like to prevent your vehicle from being eaten by mice, start now by controlling the rodent population where you most commonly park your vehicle.

About Ray Magliozzi: Ray is a Cambridge, Massachusetts native and MIT graduate. Along with his late brother Tom, Ray ran two auto repair businesses, the better known being the Good News Garage. Tom and Ray hosted a popular PBS radio program called Car Talk, which earned a Peabody Award. The two have also appeared in many films. Ray is presently still part of the Car Talk team and you can read and hear his wisdom at CarTalk.com.

Images by John Goreham.

John Goreham is a long-time New England Motor Press Association member and recovering engineer. John's interest in EVs goes back to 1990 when he designed the thermal control system for an EV battery as part of an academic team. After earning his mechanical engineering degree, John completed a marketing program at Northeastern University and worked with automotive component manufacturers, in the semiconductor industry, and in biotech. In addition to Torque News, John's work has appeared in print in dozens of American news outlets and he provides reviews to many vehicle shopping sites. You can follow John on TikTok @ToknCars, on Twitter, and view his credentials at Linkedin

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Comments

Tom (not verified)    January 23, 2024 - 4:28AM

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Mechanics, both independent and dealership, say there is much more rodent damage with soy.

Soy is a food, the first proof of concept would be to establish that animals would not be attracted to it. There are no such studies.

Mark Durand (not verified)    February 25, 2024 - 10:01PM

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Totally agree. We've have had about 10 cars located in the same area for decades. ZERO problems with rodents eating wiring...until we got 2 new Ford Explorers (2018, 2021). Both had the wiring harnesses chewed into and the cars were 60 miles apart...not kept in the same places at all. How much more proof does one need to know there is a problem???? What a disaster of stupidity. How is a car owner supposed to keep rodents from being attracted to rodent food??? This is like making ocean ships out of crackers and saying there is no proof its a problem.

mark durand (not verified)    February 25, 2024 - 9:53PM

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Yeah...not buying it. We have lived in the same area for decades and have had numerous vehicles (about 10) the whole time. ZERO problems with squirrels eating our wiring harnesses on anything until we bought 2 Ford Explorers (2018, 2021). BOTH have been disabled at TWO separate locations 60 miles apart. So these are different squirrels. How about just QUIT USING SOY! The planet contains squirrels. QUIT making wiring covering out of materials they like to eat!!! Here's a brilliant idea...make the covering out of something they DON'T LIKE to eat!!!

J Johnson (not verified)    March 5, 2024 - 5:34PM

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Lazy reporting. It doesn't take much time to google plenty of proof. Here's some more. A 2012 Subaru Outback and 2011 Toyota 4runner parked in the driveway of a house we've had for 20 years. 4runner's wires were chewed by either a squirrel or rat shortly after purchasing 4runner new, not the Subaru. We used a special tape on the 4runner wiring and no more chewing. Fast forward to 2023. Purchased a 2023 4runner but still had the 2011 4runner. Guess which one had its wires chewed? Yes, the 2023, which did not yet have the special tape. We took it in for service - over $9000! - and they gave us a 2023 loaner 4runner. We waited 3 weeks for the new wiring to come in because, amazingly there was a shortage. Gee, wonder why. And in that 3 weeks the loaner's wires were chewed!! So we had to file another claim! This is a cash cow for Toyota and other manufacturers. They are fully aware of what's happening, yet they continue to blame the customer. I'm surprised the insurance companies haven't filed lawsuits. Then again, they can just up their rates. Win win for the car manufacturers and insurance companies.

adopt-a-ferret… (not verified)    July 25, 2024 - 6:12AM

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Is there a conspiracy behind the prevalence of soy-based wiring in cars, leading to increased rodent damage and costly repairs for unsuspecting car owners?

Hilary Hargraves (not verified)    August 21, 2024 - 11:23AM

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I'm gonna call BS on your claim that Soy based wiring isn't attractive to rodents. As an aside, I have owned domesticated rats as pets on and off my entire life. I am familiar with how the species behaves.

I had a 2000 JD tractor, I was the 3rd owner starting in 2010. This tractor sat outside all the time in SW FL. It was kept in different rural areas with lots of woods and wildlife. It also lived outside when I owned it. NOT ONCE, in 14 years, did it ever experience any rodent damage. I also have a 2015 CarryAll UTV that was stored in the open - next to woods. Not once did it have any wiring damage. We have all sorts of wildlife wandering through, turkey, deer, coyote, crawfish, moles, snakes, otters, squirrels, possum, racoons, gopher toroise, soft shelled turtles and Alligator turtles and I am sure rats and mice.

Fast Forward to 2024. Traded in the 2000 JD (biggest mistake ever made) and replaced it with a 24' JD 4044M. Now it and the CarryAll sit outside with a 21' Toro Zero Turn, 22' CanAm ATV and a 23' CanAm UTV. The JD 4044M has only been on my property for 7 months. In that time the manual throttle ceased to work. Dealership discovered the wiring harness (for a manual throttle - instead of a simple cable - so stupid) has supposedly been damaged by rodents. Quick check on Tractor Forums - it appears to be a theme "Rodents ate the wiring on my (2017-2024) tractor" . It's a 5K bill. The wiring harness itself is 2K.

Tell me why out of all the vehicles parked on the same property have not been damaged by rodents if all wires are attractive?? There have been boats, cars and horse trailers also parked on an off. Nada, Zip.

Kathy Furlong (not verified)    November 11, 2024 - 6:45PM

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My 2022 Subaru Forrester had rodent
Infestation in the back seat and around the fuel tank. I keep it in the garage but I bought it online in November 2023 from Lafayette, Indiana. Cost me over $5000 which was mostly covered by insurance
I have pictures but cannot upload them