How often should I change my car oil?

It depends on oil type and driving conditions. Fully synthetic oil typically lasts 10,000-12,000 miles or 12 months. Semi-synthetic lasts 7,000-8,000 miles or 9-12 months. Mineral oil should be changed every 3,000-5,000 miles or 6-9 months. Always follow your manufacturer's recommendation as a minimum.

Does driving style affect oil change intervals?

Yes, significantly. Hard driving (high revs, towing, performance driving) breaks down oil faster. Short trips are particularly bad because the engine never fully warms up, leading to condensation and fuel dilution in the oil. Motorway cruising is the gentlest on oil as the engine stays at a consistent temperature.

What happens if I do not change my oil?

Old oil loses its lubricating properties and becomes thick with contaminants. This causes increased engine wear, reduced fuel economy, higher operating temperatures, and eventually can lead to catastrophic engine failure. Sludge can block oil passages, starving bearings and camshafts of lubrication.

Is synthetic oil worth the extra cost?

Yes, for most modern cars. Synthetic oil provides better protection at extreme temperatures, lasts longer between changes, flows better when cold, and resists breakdown better. While it costs 2-3x more per litre, the longer intervals mean the annual cost is often similar to using cheaper mineral oil changed more frequently.

Should I change the oil filter every time?

Yes, always change the oil filter at every oil change. A new filter costs very little (£5-£15) and ensures that clean oil stays clean. An old filter can restrict oil flow and re-contaminate fresh oil with trapped particles. Most garages include the filter in their oil change service.

CarCalcs

Oil Change Calculator — When Is Your Next Oil Change Due?

Calculate when your next oil change is due based on mileage, time, oil type, and driving style.

Current Mileage

Last Oil Change Mileage

Months Since Last Change

Oil Type

Driving Style

Annual Mileage

Oil Cost Per Change

Filter Cost

How We Calculate This

Oil Change Intervals

The calculator determines your recommended interval based on:

Oil type: Synthetic lasts longest, mineral needs the most frequent changes
Driving style: Hard driving and short trips reduce oil life
Time: Oil degrades over time even with low mileage

Whichever Comes First

Your oil change is due at whichever comes first: the mileage interval or the time interval. For example, with synthetic oil on mixed driving, change at 10,000 miles OR 12 months, whichever happens sooner.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.