brave-grouse-1685/10/2026

How do I figure out diminished value on a car I've owned for less than 3 months?

Still kind of in shock writing this out, but here goes.

I saved up forever to finally buy myself a brand new car — we're talking fresh off the lot, barely broken in, still had that new-car smell. Less than three months later I'm sitting at a complete stop waiting for a school bus and some guy plows into my rear end. Police report confirms it's 100% on him. His insurance accepted liability no problem.

The body shop did a solid repair job, no complaints there. But my car now has a collision on its Carfax and I know that tanks resale value. I want to file a diminished value claim with his insurance on top of the repair.

Here's my problem: my trim level is apparently pretty rare. I've been scouring every used car listing site I can think of and there are almost zero comparable vehicles for sale anywhere — let alone ones that have accident histories I can use as a comparison point. Without comps, I have no idea how to put a real number on what I've lost.

I've seen some people mention a formula called 17c that some insurers use, but I've also read it tends to lowball things badly. I don't want to just accept whatever number they throw at me if I have no way to verify it's fair.

Has anyone dealt with this kind of thing — especially on a newer or rarer vehicle where the used market is basically nonexistent? Did you hire an appraiser? Use some other method? I want to walk into this negotiation with something solid, not just their word for it.

8 replies

Most helpful first

mellow-tern-4125/10/2026
I went through almost the exact same thing a couple years back — newer car, rear-ended, accepted liability quickly but then the DV claim was a whole separate battle. The 17c formula they'll likely quote you is genuinely a lowball tool. I ended up hiring an independent appraiser who specializes in diminished value and the number he came back with was significantly higher than what the insurance company offered. The appraisal cost me a few hundred bucks but it gave me something concrete to push back with. Worth every penny in my opinion.
- cool-elk-2695/10/2026
  Worked in claims for years and I'll be straight with you — the 17c formula was literally invented by State Farm decades ago to limit payouts, and it's been widely criticized. Most adjusters know it undervalues DV but they'll use it anyway because it's defensible and most claimants just accept it.
  
  For a rare trim with no comps, your best move is a certified auto appraiser who does DV work specifically. They can build a case using broader market data, dealer interviews, and auction results rather than just direct listings. That kind of professional report carries a lot more weight if you end up disputing the number.
brave-beaver-2975/10/2026
Do NOT let the adjuster be the one who calculates your diminished value. That's like asking the other team's coach to be your referee. They will use whatever formula spits out the lowest number and present it to you like it's gospel. Get your own number first, then negotiate.
patient-marmot-3345/10/2026
A few practical things to keep in mind: document everything right now while the car is fresh off repair — photos, the repair invoice, the Carfax showing the new accident entry, all of it. Some states have specific rules about whether and how you can claim DV from a third-party insurer, so it might be worth a quick free consult with a PI attorney just to understand your rights in your state before you start negotiating. Not saying you need to hire anyone, just that knowing the rules helps.
swift-hare-9705/10/2026
Also — are you doing okay physically? Rear-end hits at a stop can cause soft tissue stuff that doesn't show up until days later. Make sure you're paying attention to any neck stiffness, headaches, or shoulder soreness that creeps up. People get so focused on the car side of things (totally understandable) that they sometimes ignore their own body until it's harder to connect to the accident.
wise-fox-4955/10/2026
Three things: 1) Get a professional DV appraisal, not a guess. 2) Don't accept the first number they offer — it's always low. 3) Put everything in writing when you communicate with the adjuster. Email only if you can help it. You'll thank yourself later.
genuine-bison-3175/10/2026
Quick question — what state are you in? The reason I ask is that a handful of states are genuinely tricky about first-party vs. third-party DV claims and it could change your whole approach. Also, did you get a written repair estimate or just let the insurance direct you to a shop? Some DRP shops are cozy with the insurer in ways that aren't always in your interest.
quick-owl-1425/10/2026
The fact that liability is already accepted is honestly a huge deal — a lot of people on here are fighting just to get that far. You're already past the hardest part in some ways. The DV fight is frustrating but it's a negotiation you can actually win with the right documentation. Hang in there.