A Car Dealer’s Scientific Guide to the 10 Worst Used Vehicles

Quality is something we all want when it comes to cars, especially older used ones. But how do we get it?

I have been studying this question in one form or another for nearly 16 years now. As an auto auctioneer, a remarketing manager and a part-owner of a wholesale auto auction, I’ve seen thousands of cars come and go through the auction block during the course of each year.

The overwhelming majority of the time, cars and trucks considered reliable in their early days would draw the strongest bids at the auctions. But it wasn’t always true; I observed some models experienced costly transmission failure just as the odometer rolled past the 100,000-mile mark, while others would exhibit everything from blown head gaskets, to chronic rust issues, to inoperative battery packs for hybrid vehicles.

Well-respected publications such as Consumer Reports and J.D. Power & Associates do an outstanding job finding defect trends among new and slightly used vehicles. However, once that specific vehicle is sold by the survey participant, there’s no access to the history of the vehicle.

As the average car owner typically keeps their vehicle for five to six years, a lot of data disappears. Because there is no tracking service covering the problems in these vehicles, the 10-year-old vehicle that everyone assumed had great reliability will at times have terrible issues. Consumer Reports’ database goes back 10 years, but the average car and truck is now 11.4 years old.

So I decided to test my personal experiences with used vehicles by using data from auto auctions and the problems dealers themselves disclose. As a frequent buyer and seller, I started my study with what I consider the key quality question for most car owners: “At what point does my car become so undesirable that I am willing to accept a wholesale price for my vehicle?”

Trade-ins are a great measurement of that emotional question. Most consumers who trade their vehicle will get a price hundreds to thousands of dollars less than retail. Car dealers not only know the wholesale market, they know the retail market as well, and are often able to get cars repaired for a lot less than most car owners.

This isn’t always the case. Clean cars can sometimes be traded-in at a retail price, and then financed to a subprime car buyer for even more money. Dealers who specialize in a given car brand are usually more effective in marketing and selling that specific name, and they also get a greater share of trade-ins from the brand — along with a better selection of clean vehicles.

To remove this bias, I decided to gather data on trade-ins sent to wholesale auctions by large used-car retailers and other regional used-car retailers that don’t cater to a single automaker. This way there wouldn’t be an over-representation of a given brand. I also employed the help of Nick Lariviere, a statistician capable of creating visuals that would make all this real-world used car data easy to understand.

Two years and over 660,000 vehicles later, we have developed a new quality index that you can find here. For now, we are focusing on brands and models. As the study continues to pool more vehicles, we’ll gradually introduce specific model year data, and even powertrain combinations, so that used car buyers can figure out where to find that older used vehicle that has truly earned its quality reputation.

So what out there is truly low quality? As far as those cars with the highest defect level at trade-in time, here are the 10 worst:

10. Mazda RX-8: Chronic engine issues resulted in Mazda extending the warranty on the RX-8’s rotary engine to 8 years and 100,000 miles for all 2004 - 2008 models. Unfortunately, a lot of RX-8s that have engine issues past that warranty period are being kicked to the curb by their owners.

9. Mazda 626: Engine issues, transmission issues and cheap interiors that just don’t wear well. Yes, there are more Mazdas on this list.

8. Lincoln LS: Extensive transmission and engine issues on all V-6 and V-8 models. Along with ungodly replacement costs.

7. Suzuki Forenza: A one generation wonder that thankfully didn’t become too popular. The Forenza’s entire powertrain originated from Daewoo, which at the time was a bankrupt automaker with substandard quality. Suzukis that are Daewoos in drag, such as the Reno and Verona, have atrocious long-term reliability.

6. Land Rover Discovery: Expensive parts. Expensive powertrains. Electronics that are apparently the spawn of Beelzebub.

5. Cadillac Catera: It’s hard to find a Cadillac with worse issues than one equipped with an older Northstar V-8 engine. However nearly 1 in 4 Cateras have severe powertrain issues, and the fit and finish of the interiors are third-world quality.

4. Mini Cooper: Bad automatic transmissions that are unusually expensive to replace. Cheap interior parts. Cheap hydraulics.

3. Mazda CX-7: Engine issues on these vehicles are legion with nearly a third of these vehicles sold with “Engine needs service” announcements at the auctions. Despite a short model run, there are more CX-7s traded-in than any other bottom performer except for Mini.

2. Land Rover Freelander: Just like the Land Rover Discovery but with a seemingly infinite number of problems. Cheap and easily breakable plastic components and hideously expensive head gasket issues have resulted in a class-action suit.

And a true shocker, the single worst used vehicle at the wholesale auctions when it comes to overall defect rate at trade-in time is…another Mazda

1. Mazda Millenia: The Mazda brand has a bit of a split personality. Their bread-and-butter models that span several generations often score average to better. But their defunct models are a no-no nadir with four of these models encompassing our bottom ten performers. Over 40 percent of Millenias are traded-in with a severe engine or transmission issue with a fairly even spread between the two.

No list can be perfect, and it wouldn’t be right if I didn’t offer at least a couple of important caveats here. There are cars out there that are worth so little money now that they go straight to the junkyards instead of the wholesale auctions: Older Chryslers with defective 2.7-liter engines, older Suzukis and Kias, and the aquatic late ‘90’s Ford Tauruses sometimes fall straight into the crusher once a major problem takes hold.

Also, if the vehicle appeared to have reliability issues, but didn’t have enough of a sample size at this point (for example: Mercury Mystique, Isuzu Axiom, Suzuki Verona), I have kept it off the list for right now.

Finally some models that have performed poorly so far, like the VW New Beetle, may have a pearl of quality in a specific engine/transmission combination within the overall swamp of trouble. Turbodiesels and five-speed manuals are usually the most reliable Volkswagens in our study. This is one of the main reasons why we are going to delve deeper. In the meantime, if you want to know how your vehicle has fared in terms of long-term quality, click here.