I don’t know about you, but after I buy a car, whether it’s used or new, I still have a sinking feeling that I could have negotiated a better deal. Maybe I didn’t get the best price despite pulling information from the many authoritative sites for car buyers — Consumer Reports, Edmunds.com, Kelley Blue Book, AutoTrader, etc.

These are all good, but recently I stumbled on a site called CarGurus.com that helped put me more at ease about the deal I got on a car. We needed help shuttling our three children to various schools and events, so this car will primarily be driven by our newly licensed 17-year-old.

We did all the usual things you need to do to shop for a car. We narrowed down the type of car we wanted — a used Honda Civic — and did our research on its suggested value.

Finally, we found a car that had all the features and options we wanted at a local dealer. We negotiated a discount off the Internet advertised price. We didn’t take the deal on the spot but gave ourselves a few days to think about it.

During our time out, I relied on my motto for big purchases: Check and then double check before you write the check. So I went back to the Internet. That’s when I found CarGurus.com.

Like many such sites, CarGurus offers lots of free information about new and used cars. But what makes the site unique is that it specifically says if it thinks the advertised prices are great, good, fair, poor, or overpriced.

CarGurus uses mathematical algorithms to analyze the vehicles that are available and then rank the listings. The listings also take into account other factors such as mileage.

The site was launched six years ago by Langley Steinert, the former chairman and cofounder of TripAdvisor. Steinert said the company makes about $15 when a customer contacts a dealer through the site. The dealer pays the fee for the lead, not the customer. The site also allows private sellers (non-dealers) to list their cars for free.

“No one is paying us to put the cars in any particular order,” he said.

During my search on the site, I saw the very car we had settled on. Based on CarGurus’ analysis, the Internet deal the dealer had listed was a “fair” price. That meant there was room to get an even better price. I noticed on CarGurus that the dealer had dropped the price twice within 30 days. During our timeout, it dropped again.

We called the dealer and asked the salesperson to apply the discount we had negotiated to the lower price. They agreed. We bought the car.

The final price we paid bumped our deal up to “good.” We drove the car off the lot feeling good about our purchase.