$2-3k? loss? Not going to happen. Not even close.
Look at 2017's for sale online.
Cargurus.com is a good source.
Look for a the option package and miles of your Passat. See what they're selling for. Then subtract $4000. That's the average mark up of any used car on a dealer lot.
Thats about what they'll give you. So if it sells for $20k, your trade in will be around $16k.
General rules of thumb for everyone:
If you paid 31,000 a year ago, and you financed more than you paid, because you owed on the previous trade in, you WILL be upside down- or owe more than the car is worth. Trading it in now willl only amplify the negative equity cycle and put you further behind. Keep a car for at least 48 months.
Most people make 3 mistakes when buying a car.
1. They trade in a car that has negative equity. (it isn't worth what they owe on the loan.) This negative equity gets absorbed into the new car loan, and now they're further in the hole. Then they keep repeating the pattern until the loan to value ratio is too high for a bank to float the loan. Most banks only lend 115-120% of the value of a car. 2 consecutive non-paid off trade in vehicle cycles will hit this number quite easily. Then they look at you to put down more money to bring it within that 115-120% range.
2. They trade out of the car too early and they've incurred more depreciation on a car than they've paid in loan payments. and they're "upside down" in terms of loan payoff vs car value.
3. They finance a car for way too long, and the car is never in positive equity territory. 60 and 72 month loans are a losing proposition. If you have to finance for 72 months, you're in the wrong vehicle. Most people trade out after 39 months.
If you are trading in and out of a vehicle often-Lease it- dont buy it. Just be sure to pre-pay for enough miles on it so you don't get hit at the end of the lease with mileage overcharges. Lease it especially if it is more than $50,000. 50k vehicles depreciate so much faster than lower price cars. The monthly payments will be less than a purchase payment, and they've proven that they're the type who doesn't ever pay off a car anyway.
Leasing a vehicle helps end the Negative equity cycle. Since a Lease is typically 3 years, you can absorb negative trade in equity and be done with it in 3 years instead of carrying it for another 72 month loan.
I could go on, but I wont.
TLDR:
Generally, wait 4 years before trading out of a car. Or you'll absorb a huge loss.
Don't finance for more than 60 months.
Lease expensive cars rather than buy them, just make sure you contract for the right number of miles you'll use during the lease term. (15k per year not 10 or 12)
If you are the type who trades out often, why would you finance it for longer than you own it? Lease it.
