Vehicle EconomicsOld Car Repairs vs New Car Payment
"My repairs cost almost as much as a car payment" is a common comparison, and a misleading one. See both the honest cash-flow comparison and the full economic answer.
Why this comes up
A $400 repair bill in the same month as a $500 new-car payment estimate feels like the decision is obvious. It usually is not, because a car payment includes principal that builds equity, while a repair bill is pure expense, and a new car brings its own depreciation and transaction cost the payment estimate alone never shows. This engine corrects the comparison on both counts: cash flow first, then the full economics.
How we calculated this
Cash flow: your annual repair budget divided by 12 against the new car's actual monthly loan payment from its price, down payment, APR, and term. Economics: the current car's full forward cost (repairs, fuel or energy, insurance, maintenance, zero financing) against the new car's net cost (real amortized financing minus ending equity, plus its own operating costs). We also solve the repair-budget ceiling where the two economic paths tie.
Worked example, using this page's own defaults: a $1,800/year repair budget is $150/month, well under the new car's $594/month payment. On full economics, though, keeping the old car still costs $25,600 against $37,679 for the new car, a $12,079 advantage for keeping, even though the monthly payment comparison looked closer.
What this means
- A repair bill smaller than a car payment is not automatically the cheaper path once equity and depreciation are counted; check both numbers on this page, not just cash flow.
- The repair-budget ceiling tells you how bad repairs would need to get, on average, before the full economics actually favor a new car, not just the monthly cash flow.
- If your repair budget is already near that ceiling, the honest next step is getting real replacement numbers, not another repair estimate.
Limitations
This model only knows the dollar figures you enter; it cannot judge the reliability risk of continuing to repair an aging car or the inconvenience of unplanned downtime. See Methodology.
Methodology
This engine combines Vehicle Economics' ownership total cost model, real amortization for the new car, and a break-even search for the repair-budget ceiling. See Methodology for the full detail.