By John Goreham

The Toyota Prius is the top-selling green car of all-time. Not only has it been a big seller for many years, but it has also been the top-selling car of any type in many key markets, such as in California. Despite gasoline prices at the low end of low, the Prius remains a high-volume car and still outsells every electric vehicle model in America. For used Prius shoppers, this is both good and bad news.

The good news is there are a lot of Prii in circulation. The bad news is they have the lowest depreciation of any green car and hold their value well even in comparison to mainstream compact cars. So a used Prius is not going to be a steal. All the more reason to look carefully at which model year one chooses to avoid trouble.

Unlike some of the cars in our Buy This Year, Not that One! reporting, the Prius has been very reliable for its entire production run for the past 15 years. The overall rate of customer complaints is relatively low but does show an interesting bell-curved shape when viewed as a timeline. That “complaints mountain” you see on the chart above from CarComplaints.com is due to just two issues and needs to be taken in context.

Shoppers should be aware of two issues with the Prius. The first is excessive engine oil consumption. Ruth S. from Hot Springs, AR, explained the problem in her 2015 CarComplaints.com post, saying, “I've loved my 2006 Prius and have always taken it to a Toyota dealer for service. In January of this year, I started to notice that it was burning oil. This is July of 2015, and I'm now burning about three quarts every 500 miles.” Perry H., of Spring Branch Texas told CarComplaints.com about his 2011, saying, “After 100,000 miles I noticed increased oil consumption. The car is burning through three quarts of oil in 2000-2500 miles. I now have 145,000 miles on the car and the problem is getting worse.” Unlike the Subaru oil consumption issue we recently reported on, the Prius engines generally don’t start their hijinks until late in life. Still, who needs the hassle?

The second issue to be aware of when shopping for a Prius is the headlight issue. The most complaints are from model years 2007 and 2008 Prius cars, but it seems to span from 2006 through 2012. LeRoy M., from  Montesano, WA, explained what is a very common problem, saying, “This problem has occurred several times. Sometimes just one light goes out, sometimes both lights. This is a real problem on rural roads at night.” Toyota has issued technical service bulletins on the issue indicating that HID bulbs don’t die quickly, but start to act up. However, some owners who had the bulbs changed still had problems afterward. CarComplaints.com reader Ashley explained, “I have changed my headlight bulb twice now, but it keeps going out. I can turn the light off, and it will come back on every time, but then it fades out. What is the problem here? This is taking a lot of time, energy, and money to fix. The internet says it is a ballast problem and I've been pulled over already! Toyota needs to fix this safety hazard.”

Given these two issues, how does one avoid them when shopping used? We suggest asking the seller if the vehicle you are considering has either of these issues if it coincides with the model year. Look at the service records and search for mention of the problem and consider walking away if they are present or if no records are available.

Because the Prius is so well loved, Car Talk wanted more insight on the issues we uncovered in our data search at CarComplaints.com. We reached out to a trusted used Toyota Prius dealership located in Metro-West Boston.  1A Auto sales in Walpole has focused on the Prius for nearly a decade. Chris  Eldoueihi told us that the oil consumption issue is not usually a problem for owners who change their oil at shorter intervals than the recommended period Toyota suggests. He says that sticking with a 5K miles oil change schedule seems to prevent the onset of the late-mileage oil consumption issue. Chris did confirm that the headlight issue is real and tells Car Talk it is really two things happening. The standard headlights are prone to having ground wire issues that can be resolved by a mechanic. He also says that the Prius does not respond well to aftermarket bulbs, and says that that factory bulbs work better. With regard to the HID headlamps, Chris says the ballast problem is real and is tricky to resolve. That job is likely going to require a dealership's involvement and may be one to look at very closely if a used Prius you are considering has any indications of the problem.

We asked Chris if he had any advice for used Prius shoppers, and he said that unlike most cars, the Prius is a great high-mileage used car. In his experience, Prius cars with high mileage remain reliable, and he says the third generation is proving to be the best yet regarding reliability.