Used Car Compatibility Checklist — What to Replace First

Priority 1 — Replace Immediately

  • Engine oil + filter — you don’t know when it was last done or what grade was used. Fresh oil is cheap insurance. Cost: £25-40.
  • Wiper blades — always worn on used cars. Cost: £15-25.
  • Cabin filter — almost certainly never changed by previous owner. Cost: £8-15.

Priority 2 — Check Within First Month

  • All bulbs — do a walkaround check on all lights. Replace any that are dim or blown.
  • Battery condition — get a free battery check at Halfords or your garage. If it’s over 4 years old, replace proactively.
  • Spark plugs — if no service history, change them. Worn plugs hurt fuel economy from day one.

Total Cost

Replacing everything in Priority 1 costs approximately £50-80 in parts doing it yourself. It’s the single best investment you can make in a used car’s reliability and gives you a clean baseline for future maintenance.

Frequently Asked Questions

Should I change everything even if the seller says it’s been done?

Unless you have documented proof (dated receipts or stamped service book), assume nothing has been done. It’s a small cost for peace of mind.

What if the used car has full service history?

Check the most recent service date and what was included. If the last service was over 6 months ago, at minimum change the oil and check the rest.

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