That is money gone before you pay a cent of interest, and it is larger than most repair bills. The usual advice compares your quote against what the car is worth. The real comparison is against what replacing it costs.
Fuel use assumed — petrol 9.0 L/100km, diesel 7.5 L/100km, hybrid 4.8 L/100km, electric 16.5 kWh/100km. A new replacement is assumed 10% more efficient than an older car on the same fuel.
What is deliberately left out — registration renewal, comprehensive insurance, routine servicing and tyres. You pay these whichever car you drive, so including estimates on both sides adds noise without changing the answer. Insurance is usually somewhat higher on a more valuable car and servicing somewhat lower on a newer one; those two pull in opposite directions. If your case is unusual, count them yourself.
Also not counted — safety and reliability, which are not costs but are real reasons to replace a car; the opportunity cost of cash spent outright; and any manufacturer warranty on the replacement.
The common advice is never to spend more repairing a car than it is worth. It sounds prudent, and it quietly compares your repair quote against nothing at all.
Replacing a car costs money the moment you do it. Stamp duty, transfer and registration are unrecoverable. Then the replacement starts losing value immediately — commonly 15–20% in the first year on a new car. On a $40,000 purchase that is $6,000–$8,000 gone in twelve months, before any interest.
Registration, insurance, servicing and tyres are payable whichever car sits in the driveway. Adding estimates for both sides makes a comparison look thorough while burying the actual decision. We model the costs that genuinely differ, and say plainly which ones we left out.
RACV's car running costs survey, which has run for more than 50 years, finds purchase price and finance can account for as much as 80% of total ownership cost once repayments are counted. Keeping a car you already own skips the largest cost in car ownership.
An old car's future repair bill is unknowable. Rather than invent an average, the calculator asks what you would budget and then shows what a second major breakdown does to the result. If one more repair flips the verdict, the decision is close — and reliability matters more than the arithmetic.
This calculator will tell you to keep your car more often than not, because that is usually what the arithmetic says. It is not always right, and cost is not the only thing that matters.
A single $5,000 repair is usually worth it. Three $2,000 repairs a year, every year, is a different pattern — raise the future repairs budget until it reflects what has actually been happening, and watch the verdict change.
Structural rust, failed airbags, no electronic stability control, or a car that is no longer reliable enough for the driving you do. None of these appear in a cost comparison, and all of them can be decisive on their own.
Swapping a thirsty older car for an efficient hybrid or electric one over high annual kilometres can shift several thousand dollars across a long ownership period. Set your real annual kilometres and both fuel types above to see whether it is enough to matter in your case.
If being without a car costs you income, or you cannot absorb an unplanned $4,000 bill, paying more for predictability is a legitimate financial decision rather than a failure of arithmetic. Budget certainty has value the calculator cannot price.
Often yes — and this is the most common mistake in the decision. The rule of thumb says never spend more on a repair than the car is worth, but that compares the repair bill against zero rather than against the real alternative.
Replacing is not free. A new car in Australia loses roughly 15–20% of its value in the first year alone, on top of stamp duty, transfer and registration, and any loan interest. On a $40,000 replacement, first-year depreciation alone is commonly $6,000–$8,000. A $5,000 repair on a $6,000 car can still be the cheaper option over three years. The right test is total cost over the years you plan to keep driving.
Published Australian estimates put first-year depreciation at roughly 15–20% of the purchase price, then about 10–15% of the remaining value each year after. Over five years many cars lose 50–60% or more of what you paid.
This calculator defaults to the midpoint of those ranges — 18% in year one and 12% a year after — and lets you change both, because depreciation is the single assumption that decides borderline cases. A used replacement avoids the steep first-year drop, which is why new and used are treated differently.
Only the costs that actually differ. Repairing and keeping: the repair bill, a realistic budget for future unscheduled repairs, and the value your current car still loses over the period. Replacing: stamp duty, transfer and registration, loan interest if you finance it, and depreciation on the replacement, less whatever you get for the old car.
Costs that are broadly the same either way — registration renewal, comprehensive insurance, routine servicing, tyres — largely cancel out, and adding estimates for both sides adds noise without changing the answer. Fuel is the exception, because a materially more or less efficient replacement changes running costs, so energy is modelled separately.
Yes. Every state and territory charges motor vehicle stamp duty — vehicle registration duty in Queensland, vehicle licence duty in Western Australia — when a vehicle is transferred into your name, whether you buy from a dealer or privately.
Rates differ sharply. Queensland charges by engine type from $2 to $4 per $100 of value; NSW charges 3% up to $45,000 then a premium band above it; the ACT charges by emissions category. On a $40,000 replacement, duty typically runs $1,200–$1,700. Duty for all six jurisdictions is built into the replacement cost above — the car stamp duty calculator breaks it down further.
You cannot know, and any calculator claiming otherwise is guessing. What you can do is set a realistic annual budget for unscheduled repairs and test how sensitive the decision is to it.
That is why the future repairs budget is an input rather than an invented average, and why the calculator shows a second-breakdown test. If one more repair flips the answer, the decision is genuinely close — and reliability, warranty and your tolerance for being without a car matter more than the arithmetic. An independent mechanical inspection, or your own service history, is better evidence than any average.
For most Australians, keeping the existing car is cheaper, because the largest single cost of car ownership is acquiring the car rather than running it. RACV's long-running car running costs survey finds purchase price and finance can account for as much as 80% of total ownership cost once repayments are counted.
Replacing usually wins on cost only when the repair bill is very large relative to the car's remaining value, when repairs are recurring, or when a much more efficient replacement meaningfully cuts fuel spending over a long ownership period.