Should I Keep My Old Car
Decide whether to keep your aging vehicle or replace it. Compare running costs and reliability risks.
Keep Current Car
Estimate current market value using Parkers or AutoTrader
Insurance, fuel, tax, maintenance combined
Buy New Car
Loan/finance payment only (not insurance/fuel)
Insurance, fuel, tax combined (usually lower than old cars)
The Maths Behind Keep vs Replace
An old car has the lowest possible monthly cost: nothing on finance, low road tax (or zero for very old cars), insurance often £20 to £50 cheaper a month than a new equivalent, and depreciation already taken. Repairs and a slightly higher fuel bill are the offsetting costs. A new car has the opposite profile: high monthly finance, fresh depreciation eating £200 to £400 a month, low fuel and maintenance, full warranty cover.
The break-even is simpler than people think. Add up: annual repairs + annual fuel + annual insurance + annual road tax for the old car. Compare against: annual finance + annual fuel + annual insurance + annual road tax for the new car (depreciation is already inside the finance number for a sensible 36 to 60 month deal). When the old-car total exceeds the new-car total, replacement is cheaper. Most cars cross this line somewhere between 12 and 18 years old, depending on annual mileage and reliability.
When Repairs Tip the Decision
A single £1,200 repair on a 14-year-old car feels enormous, but spread across 24 months of avoided £400 finance payments, it is actually £350 a month of saved cost vs new. The number to watch is annual repair spend rather than individual bills. Once your annual repair bill regularly exceeds the annual depreciation of an equivalent new (or newer used) car, the old car is genuinely costing more to keep.
Use the calculator's break-even repair figure: it shows how high annual repairs would need to climb before replacement becomes cheaper. For a 12-year-old £4,000 car against a £25,000 new replacement at £400 a month, the break-even is typically £3,000 to £4,000 per year in repairs. Below that, keeping the car wins; above that, replacing wins.
The Hidden Costs People Forget
Insurance often drops every year on an older car as its value falls; new cars have higher premiums for years. Road tax (VED) on cars registered before April 2017 can be substantially lower than on new cars, particularly for low-displacement engines. ULEZ and clean-air zones are the opposite story: pre-2015 petrol and pre-2016 diesel cars pay £12.50 a day in London ULEZ and similar charges in Birmingham and Bristol Clean Air Zones, which adds up to around £4,500 a year for a London commuter; that alone funds a newer compliant car.
Reliability risk is harder to quantify but real. A 15-year-old car that has been well-maintained will probably keep going for years; one with a patchy service history can develop expensive problems suddenly. The break-even calculation assumes average repair costs; if your car is on borrowed time, the actual cost can spike unpredictably. The right answer is often to set aside a 'repair reserve' equal to 6 months of new-car finance costs, and replace if a single repair would consume more than that.
Typical UK Old Car vs New Car Annual Cost (£25,000 replacement)
| Category | 10-year-old £4k car | New £25k car |
|---|---|---|
| Finance/depreciation | £0 (depreciation done) | £4,800 (60-month loan) |
| Fuel (10k miles, 35 mpg vs 50 mpg) | £1,860 | £1,300 |
| Insurance | £480 | £720 |
| Road tax | £200 | £190 |
| Repairs and servicing | £1,200 | £200 (in warranty) |
| MoT | £55 | £0 (first 3 years) |
| Annual total | £3,795 | £7,210 |
Frequently Asked Questions
What is the average lifespan of a UK car?
Around 14 years and 150,000 miles on the road, though many well-maintained cars run for 200,000+ miles. Japanese makes (Toyota, Honda, Mazda) and German diesels (BMW 320d, Mercedes E-Class) are the longest-living mainstream choices. American and French cars typically retire 2 to 3 years earlier on average. The brand of the car you currently own is one of the strongest predictors of how long it will keep going at low repair cost.
Is it worth fixing an old car or scrapping it?
If the repair cost is more than 50% of the car's market value, scrapping or selling for parts is usually the cheaper move. A £1,500 repair on a £4,000 car is reasonable; a £2,500 repair on a £3,000 car is almost always not. Get a price for the repair, look up the car's market value on Auto Trader's valuation tool, and apply the 50% rule.
Does ULEZ change the maths?
Yes, dramatically, if you drive in London regularly. A non-compliant car in ULEZ costs £12.50 a day. At 5 days a week of London driving that is £3,250 a year, which on its own funds a 4-year-old compliant car at around £200 a month finance. If you live in a ULEZ-affected area and your car is non-compliant, replacement is almost always financially obvious.
Should I trade in or sell privately?
Selling privately on Auto Trader, eBay or Gumtree typically nets 15 to 25% more than trade-in value, though it takes more effort. For cars worth under £2,000 the difference shrinks because dealers are less aggressive on low-value trade-ins. Webuyanycar and Motorway are middle-ground options: less hassle than private, slightly better prices than dealer trade-in.
What about going used instead of new?
A 2 to 3 year old used car with 20,000 to 30,000 miles is the strongest value proposition in the UK car market. You skip the worst of the depreciation (which the first owner has paid), still get decent reliability and a part-warranty in some cases, and pay 30 to 50% less than new. The calculator compares against any replacement cost, so you can model new vs used vs keep on equal footing.
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