Page published October 27, 2026
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This door answers a different question from the keep it 10 years calculator. That tool compares keeping against buying over a whole decade. This page answers the question that lands all at once: this repair, this bill, right now, is it worth paying?
The threshold, in plain arithmetic
Take a paid off car that costs $23,467 to run for the next 5 years without any big repair: insurance $150 a month, or $9,000; fuel $9,967, from 12,000 miles a year at 25 miles per gallon and $4.153 a gallon (the EIA national average for the week ending November 2, 2026) over 5 years; upkeep $900 a year, or $4,500. Take a replacement new Toyota RAV4 at a 5-year total of $40,957 on the site standard basis. The threshold is the replacement total minus the old car running costs: $40,957 minus $23,467 equals $17,490. Any single repair below $17,490 keeps the old car cheaper over the next 5 years in this example. Any single repair above it, and replacing wins on cost alone.
Worked example: a $4,500 transmission repair
Our common repair costs page puts a transmission replacement at $2,500 to $8,000 or more, so $4,500 sits inside the published range. Add it to the old car running costs: $23,467 plus $4,500 equals $27,967 over the next 5 years. The replacement RAV4 is $40,957. Fixing wins by $12,990 in this example, even though $4,500 is a painful bill. The same logic holds for a catalytic converter at $1,000 to $3,000 in the published range: even the top of that range leaves the old car far ahead on 5-year cost.
Formula
The threshold is the replacement total minus the old car running costs: $40,957 minus $23,467 equals $17,490. Any single repair below $17,490 keeps the old car cheaper over the next 5 years in this example. Any single repair above it, and replacing wins on cost alone. The old car running costs are three lines: insurance $150 a month, or $9,000 over five years; fuel $9,967, from 12,000 miles a year at 25 miles per gallon and $4.153 a gallon over 5 years; upkeep $900 a year, or $4,500. Added together, $9,000 plus $9,967 plus $4,500 equals $23,467.
The worked example is a $4,500 transmission repair, inside the published range of $2,500 to $8,000 or more. Add it to the old car running costs: $23,467 plus $4,500 equals $27,967 over the next 5 years. The replacement RAV4 is $40,957. Fixing wins by $12,990 in this example. The same logic holds for a catalytic converter at $1,000 to $3,000 in the published range: even the top of that range leaves the old car far ahead on 5-year cost.
When the threshold is not the whole answer
Three things can overrule the math. First, repeat repairs: one $4,500 repair is cheap against $17,490, but a second big repair next year and a third the year after eat the threshold fast, so count the last two years of bills, not just this one. Second, reliability: a car that strands a household has a cost no total captures, especially when work, school, or care duties depend on it starting. Third, safety: a car whose structure, brakes, or airbags are compromised is not a math problem. If any of those three apply, replacing can be right even when the threshold says fixing is cheaper.
For the decade version of this decision, use the keep it 10 years calculator, and for what repairs typically cost before you get a quote, see how much common car repairs cost.
For the same decision run as full 5-year totals on both sides against a used $20,000 replacement, see repair or replace your car.
Figures: repair ranges from the Driveonomics common repair costs page. Replacement total is the RAV4 5-year total on the site standard basis: 12,000 miles a year, gas at $4.153 a gallon (the EIA national average for the week ending November 2, 2026), 7% sales tax as a site example, $900 in fees, 10% down, 8% APR over 60 months. Old car running costs are the stated example inputs, not a quote for any specific car.
Educational estimates only, not financial, tax, legal or insurance advice. Every figure on this page is a typical example worked from the inputs stated on the page, not a quote for a specific car, loan, or driver. Your rate, insurance, fuel use, and resale value will move your total. See Terms.
Calculation transparency
Scope. One repair decision, right now: a paid off car against replacing it with a new Toyota RAV4, over the next 5 years. The threshold, not the size of the bill alone, is what decides it.
Rules and time period. Old car running costs are the stated example inputs, not a quote for any specific car: insurance $150 a month, fuel 12,000 miles a year at 25 miles per gallon and $4.153 a gallon (the EIA national average for the week ending November 2, 2026) over 5 years, upkeep $900 a year. Replacement total is the RAV4 5-year total on the site standard basis: 12,000 miles a year, gas at $4.153 a gallon, 7% sales tax as a site example, $900 in fees, 10% down, 8% APR over 60 months. Repair ranges from the Driveonomics common repair costs page.
Scope and limitations. Educational estimate only. Three things can overrule the math: repeat repairs, because a second big repair next year and a third the year after eat the threshold fast, so count the last two years of bills, not just this one; reliability, because a car that strands a household has a cost no total captures; and safety, because a car whose structure, brakes, or airbags are compromised is not a math problem. If any of those three apply, replacing can be right even when the threshold says fixing is cheaper. Insurance quotes, gas prices, and local rates vary by driver and address. Get a real quote for the same car, coverage, and loan before you decide.
Source links checked November 6, 2026. Figures: Repair ranges from the Driveonomics common repair costs page, transmission replacement $2,500 to $8,000 or more, catalytic converter $1,000 to $3,000; replacement total is the RAV4 5-year total on the site standard basis; EIA national average gas $4.153 a gallon, week ending November 2, 2026; Experian State of the Automotive Finance Market Q2 2026, average rates 6.35% on new cars and 11.19% on used cars, for context against the 8% example rate.
Primary sources: EIA Gasoline and Diesel Fuel Update; Experian average car payment; Toyota RAV4 true cost; How much do common car repairs cost. How the numbers are calculated is written down on the methodology page, and every source is listed on the sources page.
Definitions
Threshold. The repair bill at which replacing wins: the replacement 5-year total minus the old car 5-year running costs without the repair. In the example, $17,490.
Running costs. What the old car costs to run for the next 5 years without any big repair: insurance, fuel, and upkeep. In the example, $23,467.
Paid off car. A car with no loan left, so no payment in the running costs. The example car is paid off.
Replacement total. The 5-year total of the replacement car. In the example, a new Toyota RAV4 at $40,957 on the site standard basis.
Transmission repair. Fixing the gearbox that sends the engine power to the wheels. The published range is $2,500 to $8,000 or more for a replacement; the example repair is $4,500.
Catalytic converter. A box in the exhaust that cleans up the fumes before they leave the tailpipe. The published range is $1,000 to $3,000.
APR. Annual percentage rate, the yearly interest rate on the loan. This example uses 8%. For context, Experian reported average rates of 6.35% on new cars and 11.19% on used cars in the second quarter of 2026.
Questions people actually ask
At what repair bill does replacing my car win?
It depends on the replacement and on what the old car costs to run, but the threshold is the replacement 5-year total minus the old car 5-year running costs without the repair. In the example on this page, a replacement RAV4 at $40,957 minus old car running costs of $23,467 gives a threshold of $17,490, so any single repair below $17,490 keeps the paid off car cheaper over the next 5 years.
Is a $4,500 transmission repair worth paying?
On cost alone in the example on this page, yes. The old car costs $23,467 to run for 5 years without the repair, so with a $4,500 repair it costs $27,967, against $40,957 for a replacement RAV4, a saving of $12,990. Repeat repairs, reliability, and safety can still argue for replacing, but a single bill of that size does not.
How is this different from the keep it 10 years calculator?
The keep it 10 years calculator compares keeping a car against buying over a whole decade, as an interactive tool. This page answers the single repair decision: this bill, right now, against a 5-year replacement total. Different horizon, different question, and a worked threshold instead of a tool.
What if my car needs another big repair next year?
Then add it to the threshold test. One $4,500 repair is cheap against a $17,490 threshold, but two or three big repairs in successive years use the threshold up quickly. Count the last two years of repair bills alongside this one before deciding, and weigh reliability and safety alongside the money.
How much does fixing save in the transmission example?
Fixing wins by $12,990 in this example. The old car costs $23,467 to run for 5 years without the repair, so with a $4,500 repair it costs $27,967, against $40,957 for a replacement RAV4, even though $4,500 is a painful bill.
Related: If the car has high miles, see whether a high-mileage car is worth buying.
Related: If you buy, see the new vs. used comparison.
Related: Check what you can afford before you decide. See how much car you can afford.