How Often Should You Change Engine Oil? A Practical Guide

There is no single interval for every engine. Learn how your maker, the type of oil and the way you drive decide when to change engine oil, and the signs it is time sooner.

There is no single number that fits every engine. How often to change engine oil depends on what your engine maker specifies, the type of oil in the sump, and how you drive. The reliable answer is in your owner's handbook, and this guide explains how to read it and when to change oil sooner.

The short answer: how often to change engine oil

• Follow the handbook first: the maker gives an interval in distance, in time, or both. Whichever comes first is the one to follow.
• Time counts too: oil ages even when the car barely moves, so a car driven rarely still needs its oil changed on schedule.
• Hard use shortens it: short trips, heavy loads, dust, towing and extreme heat or cold all call for earlier changes.

Why engine oil needs changing

Engine oil does more than lubricate. It carries heat away, holds soot and dirt in suspension, and neutralises acids formed by combustion. Over time three things happen:

• The additives that protect against wear, corrosion and deposits are used up.
• The oil collects soot, fuel and moisture, especially on short journeys where the engine never fully warms up.
• Heat and oxidation slowly change how the oil flows.

Once the oil can no longer do these jobs, wear and deposits increase. A change restores the protection the engine was designed for.

What decides your oil change interval

1. The engine maker's recommendation

This is the starting point. Handbooks give an interval for normal use and often a shorter one for severe use. Some vehicles also have an oil life monitor, which estimates oil condition from how the engine has been run. If your vehicle has one, follow it together with the handbook.

2. The type of oil

Fully synthetic oils generally resist heat and ageing better than mineral oils, which is why many modern engines specify them and allow longer intervals. The interval still comes from the maker: a better oil does not mean you may ignore the handbook. Always match the viscosity grade and the performance standard the maker asks for, for example an API or ACEA specification. If you are unsure what a grade means, read our guide to 5W-30 vs 5W-40 engine oil.

3. How and where you drive

Many drivers are in the "severe use" group without realising it. Typical severe conditions include:

• Frequent short trips where the engine does not reach full temperature.
• Stop-and-go city traffic and long idling.
• Towing, carrying heavy loads or driving in hills.
• Dusty roads or construction sites.
• Very hot or very cold climates.

If this describes your driving, use the shorter interval in the handbook, or change oil earlier.

Signs your oil may need changing sooner

Do not wait for a warning light. Check the oil level and look at the oil regularly on the dipstick.

• The oil is very dark and thick, or feels gritty between your fingers.
• The oil level drops between changes and you need to top up often.
• The engine sounds noisier than usual, particularly at start-up.
• You notice a burning smell or the oil pressure warning light comes on. Stop safely and have the engine checked.

Dark oil alone is not a fault. Oil darkens because it is doing its job of holding soot in suspension. Judge by the interval, the level and the condition together.

Changing the oil filter

The filter traps particles, so a new filter is normally fitted with every oil change. Fitting fresh oil through a clogged filter wastes part of the benefit.

What happens if you leave it too long

Old oil protects less. Deposits can build up, parts wear faster and fuel economy can suffer. In the worst case, sludge can block oil passages. The cost of an oil change is small compared with the cost of engine repair.

Quick checklist

1. Read the interval in your handbook, in distance and in time.
2. Decide whether your driving counts as severe use.
3. Use the viscosity grade and standard the maker specifies.
4. Replace the filter with the oil.
5. Check the level regularly between changes.

Need help choosing an oil that meets your engine's specification? Contact the TexLube team and we will point you to the right grade.