Interim vs Full vs Major Car Service: Which One Do You Need?
When you book a service you'll often be asked to choose between interim, full and major — but most people aren't sure what the difference is. Here's a straight comparison of all three levels, what each includes, and how to choose the right one for your car and mileage.
Quick comparison
The three service levels are essentially building blocks — a full service includes everything in an interim, and a major adds everything a full includes on top.
| What's included | Interim | Full | Major |
|---|---|---|---|
| Engine oil & filter | ✓ | ✓ | ✓ |
| Fluid top-ups (coolant, brake, screen wash) | ✓ | ✓ | ✓ |
| Tyre, brake & light inspection | ✓ | ✓ | ✓ |
| Air filter replacement | — | ✓ | ✓ |
| Cabin pollen filter | — | ✓ | ✓ |
| Spark plugs (petrol) / fuel filter (diesel) | — | ✓ | ✓ |
| Full brake & suspension inspection | — | ✓ | ✓ |
| Brake fluid replacement | — | — | ✓ |
| Coolant flush & replacement | — | — | ✓ |
Interim service — for high-mileage drivers, every 6 months
An interim service is designed to be done halfway between full services if you cover a lot of miles. The main job is changing the engine oil and filter, which degrades faster on high-mileage vehicles. At 6 months or 6,000 miles of hard use, oil can become too contaminated to protect the engine properly.
Who needs it: Drivers who cover 12,000+ miles a year and want to keep oil fresh between full services. Low-mileage drivers who only do the occasional short trip don't usually need an interim service.
Full service — the standard annual service
A full service is the right choice for most cars once a year. It covers everything in the interim service but also replaces filters (air, pollen, fuel or spark plugs depending on engine type) and includes a more thorough inspection of brakes, suspension and exhaust.
Who needs it: Any car that hasn't been serviced in the last 12 months or 12,000 miles. This is the default recommendation for most everyday drivers.
Major service — every 2 years for thorough maintenance
A major service adds fluid replacements that don't need doing every year. Brake fluid is hygroscopic — it absorbs moisture over time, which lowers its boiling point and can affect braking performance. Coolant degrades similarly. Both should be replaced every 2 years regardless of mileage.
Who needs it: Cars that are 2 or more years past their last brake fluid or coolant change. If you're not sure when these were last done, a major service is a sensible reset.
Not sure which you need? Call us and tell us your mileage and when the car was last serviced. We'll tell you honestly which level is right — and we won't upsell you to a major if a full is all you actually need.
Service interval: by time or mileage?
The rule of thumb is whichever comes first — time or mileage. Engine oil degrades through time as well as use, so a car that only does 3,000 miles a year still needs a full service every 12 months. If you cover very high mileage, you may hit the mileage trigger before the time trigger.
Does servicing need to happen at a main dealer?
No. Under UK and EU Block Exemption rules, having your car serviced at an independent garage using manufacturer-spec parts does not void your warranty. We stamp your service book and issue a detailed service invoice — the same evidence a dealer would provide. See: Car service cost in Ashford 2026.
Book a service at our Ashford garage
We're on Feltham Road in Ashford TW15 — call us or book online. Tell us your mileage and last service date and we'll confirm which level is right for your car.