How Carvest Works

Carvest models two futures over the same 36 months: keeping the car you have, or buying the car you're considering. For each, it adds up the cash you would spend and estimates what the car would be worth at the end, minus any loan still owed. The difference between those two positions is the financial result.

36 months is long enough to show depreciation, loan and repair effects, and short enough that the estimates stay reasonable.

• Loan payments actually made during the 36 months, on either car.
• Cash paid at purchase, plus sales tax and mandatory government fees.
• Insurance, fuel or charging, maintenance, likely repairs, tires and subscriptions.
• Depreciation, shown as the difference between today's value and the estimated value at month 36.

• Keeping: your remaining scheduled payments are counted as you make them. Whatever balance is left after 36 months is subtracted from the car's ending value.
• Buying: your current loan payoff is subtracted from the trade-in value. Positive trade equity reduces what you finance; negative equity is added to the new loan. Your old loan's payments aren't counted again.
• "I'm not sure" about the payoff: Carvest estimates it from your payment and payments left, assuming a 7% rate, and labels it as an estimate. It is always a little below the total of your remaining payments, because that total includes future interest. Your lender's payoff quote is more accurate and can be entered at any time.
• A blank loan is never treated as paid off.

Carvest shows two answers, and they can differ.

• The financial winner is purely the money: which choice leaves you better off after 36 months.
• The overall KEEP/BUY recommendation also weighs how much better the other car is (Upgrade Score) and how well it matches what you told Carvest you care about (Your Fit).

How much each part counts depends on your answer to how you're deciding: for the smartest value, the money counts for half; for a balance, 40%; for getting the car you really want, 30%. The Upgrade Score counts for 15% in every case and Your Fit for the rest. The overall score must reach 55 out of 100 before Carvest recommends buying.

If you skip the personal questions, Carvest shows the financial result as its answer.

Even at 55 or above, three safeguards keep the answer at KEEP:

• Very large cost: buying would cost at least $30,000 more, and at least 75% of the other car's price. BUY is only allowed if you chose "the car I really want," Your Fit is 90 or higher and the Upgrade Score is 75 or higher.
• Poor match: the other car scores below 20 on the Upgrade Score and below 50 on Your Fit.
• Little real upgrade: the Upgrade Score is below 20 and the money favors keeping. BUY is only allowed if you chose "the car I really want," Your Fit is 90 or higher and the extra cost is modest (no more than $7,500 and 10% of the car's price).

The Upgrade Score answers one question: how much better a vehicle is the other car? It doesn't include price, so an expensive car can still score as a strong upgrade.

• Newer and lower mileage: up to 25 points
• Reliability improvement: up to 15 points
• Lower running costs: up to 15 points
• Vehicle and feature step-up: up to 45 points

Your Fit is optional. It scores how well the other car matches the priorities you pick, such as reliability, running costs or features, compared with your current car, and how comfortable you are with the cost difference. Missing information counts as neutral, never against a car. Your Fit never changes the financial result or the Upgrade Score.

Live data from outside sources

• Vehicle details and VIN decoding: NHTSA vehicle database (U.S. government).
• Fuel economy ratings: EPA (fueleconomy.gov).
• Gas and diesel prices: weekly U.S. Energy Information Administration data for your state or region.
• Market value of your car: MarketCheck market data. A second valuation provider is combined with it only when that provider is switched on for live use.
• Nearby listings: live dealer inventory from MarketCheck.
• Trims and optional equipment: CarsXE, used only to describe the car, never to set its price.

Carvest estimates

• Future value: one depreciation model based on age and mileage, applied the same way to both cars.
• Maintenance, repairs and tires: Carvest's own model by vehicle age and mileage.
• Electricity cost and fuel price when live data isn't available.
• Car value when valuation providers can't return one, based on the car and your inputs.
• Sales tax and fees: rules built from state government sources, which can lag recent changes.

What you enter

Insurance, loan details, purchase price, interest rate and trade-in offer come from you. Every estimate is labeled in your results and can be replaced with your own number.

• Results are estimates. Real prices, values and repair bills will differ.
• Carvest doesn't inspect the car, check your credit or see your lender's exact payoff.
• Depreciation isn't adjusted for brand or model; some cars hold value better or worse.
• Leasing isn't modeled.
• Carvest doesn't sell cars, loans or insurance, and isn't financial advice.

For specific situations, see should I keep my car or buy a new one or the full list of guides.