There's a simple rule underneath a confusing amount of marketing: whichever interval your car reaches first — the mileage figure or the time figure — is the one that applies. Neither number works alone.
Why isn't mileage enough on its own?
Because engine oil, brake fluid and coolant all degrade just by sitting in the engine, whether the car is driven or not. Oil picks up moisture and loses its additive package over time; brake fluid absorbs water from the air through microscopic pores in rubber seals; rubber hoses and belts age with heat cycles, not just miles. A car that does 3,000 miles a year isn't "due less often" — it's still due on the calendar.
Why isn't a fixed date enough either?
Because wear components — brake pads, tyres, filters — respond to use, not time. A car doing 20,000 miles a year will wear its consumables faster than the calendar interval alone would catch. That's why both numbers exist on the same schedule: one protects against age, the other against use.
So how do I know which one applies to my car?
Check the figure in your handbook or service history, then compare both your mileage since the last service and the time since the last service. Whichever limit you've already crossed is the one that's due. If you're not sure where you stand, that's something a garage can check from your service record rather than something to guess at.
Does it matter whether I book a full service or an interim service?
Yes — they're not interchangeable, and one doesn't replace the need for the other at the right interval. An interim service is the shorter check done roughly midway through the full-service cycle, mainly an oil change plus a safety check; a full service is the complete item-by-item job. Skipping a full service and only doing interims doesn't reset the clock on the parts only a full service checks. For current prices on each, see How Much Is a Full Service in Wrexham? and How Much Is an Interim Service in Wrexham?.
What does ONEFIX actually do differently here?
Every service at ONEFIX — full or interim — includes a written digital vehicle health check with photographs, so you're not just told "it's fine"; you can see the brake pad thickness or the tyre tread for yourself. And nothing gets added to the job without a written quote first, so checking where you stand against your interval doesn't commit you to anything.
What if I've genuinely got no idea when my car was last serviced?
That's common, and it isn't a problem you need to solve before booking. Start from what you do know — current mileage and roughly how old the car is — and let a health check establish the actual condition of the things that matter, rather than guessing backwards from a date nobody wrote down.
Will I be charged before I've agreed to anything?
No. ONEFIX quotes a price in writing before any work starts, and nothing is carried out that hasn't been approved — whether that's the service itself or anything the health check turns up along the way.
What should I actually do if I'm not sure?
Bring in your service history, or just your registration if that's what you've got, and ask ONEFIX to check your mileage and the time since your last service against the manufacturer's interval. This page is about which interval your car has actually reached — not what either service costs.
Book a service at ONEFIX once you know which interval you've reached.