FAQs

The right engine oil is the one that matches both the viscosity grade and the specification your vehicle's manufacturer sets. The grade, such as 5W-30, describes how the oil flows. The specification, such as ACEA C3 or VW 504 00, is the performance standard it must meet.

You'll find both in your owner's handbook. Or enter your UK or Irish registration into Find My Oil to see every Duckhams oil that fits your vehicle.

They're SAE viscosity grades, which describe how thick the oil is at different temperatures. The first number shows how easily the oil flows from cold: the lower it is, the faster oil reaches the engine at start-up. The second number shows how thick the oil stays at running temperature: the higher it is, the thicker the oil.

So 5W-30 flows more easily from cold than 10W-40, and 5W-40 stays thicker when hot than 5W-30.

The W stands for winter, not weight, which is a common mix-up. The number before it shows how well the oil flows in cold conditions. A 5W oil flows more easily from a cold start than a 10W or 15W oil. That matters because much of an engine's wear happens in the first moments after start-up, before the oil has fully circulated.

Only if your manufacturer lists it. Many handbooks list more than one grade, sometimes depending on climate, and any listed grade is fine to use. An unlisted grade can slow oil flow at start-up or reduce protection at running temperature, and on newer vehicles it may affect your warranty.

Whichever grade you use, it must also meet the specification your manufacturer requires. Find My Oil shows every Duckhams oil that suits your vehicle.

Oils of the same grade and specification can be mixed, so topping up with a different brand is fine if you need to. Avoid mixing different grades or specifications, as the mix may no longer meet the specification your engine needs. Where you can, top up with the same oil that's already in the engine. If you've had to mix, go back to the correct oil at your next change.

Fully synthetic oil is made from highly refined or chemically engineered base oils. It stays stable at high temperatures, flows well from cold and lasts longer between changes, so it suits most modern engines and long-life service intervals.

Semi-synthetic oil blends synthetic and mineral base oils for a balance of performance and price. Mineral oil is refined from crude oil and suits many older and classic engines.

Your manufacturer's grade and specification will usually point you to the right type.

It can, though rarely straight away. A one-off top-up with the wrong grade is unlikely to cause harm, but replace it at your next opportunity. Over time, the wrong oil can increase wear, reduce protection at start-up and, on vehicles with a diesel or petrol particulate filter (DPF or GPF), cause the filter to clog.

If you've added a different fluid altogether, such as gearbox oil or coolant, don't drive the vehicle. Get advice from a garage.

No. The best oil for your vehicle is the one that meets your manufacturer's grade and specification, whatever it costs. A premium oil that doesn't meet the required specification won't protect your engine better, and on modern engines with a particulate filter it can cause harm. A higher price often reflects a more demanding specification or a better base oil, which only matters if your engine needs it.

Yes, in most cases, as long as the synthetic oil meets the grade and specification your manufacturer sets. Mineral and synthetic oils are compatible, so you don't need a special flush. The idea that synthetic oil causes leaks in older engines dates from early formulations; modern oils don't damage seals.

On a high-mileage engine with worn seals, though, a synthetic oil can show up leaks that were already there, so check the oil level more often after switching.

Not on its own. Your engine still needs the grade and specification its manufacturer set, however old it is. Mileage and condition matter more: a high-mileage engine may use some oil between changes, so check the level regularly.

Classic engines are the exception. Many were built before modern oil standards and need a mineral oil with higher levels of zinc (ZDDP) to protect flat-tappet camshafts. Our Duckhams Classic range is made for these engines.

A small overfill, just above the maximum mark, is unlikely to cause harm, but more than that can. Too much oil can be whipped into foam by the crankshaft, which reduces lubrication and can force oil past seals. Some engines may also burn the excess, damaging the catalytic converter or particulate filter.

If the level is well above the maximum mark, have the excess drained before driving any distance.

Viscosity (the grade, such as 5W-30) only tells you how thick the oil is. The specification tells you what the oil can do: how well it controls wear, deposits and sludge, how long it lasts, and whether it's safe for your exhaust after-treatment. Two 5W-30 oils can perform very differently.

An oil with the right grade but the wrong specification can still wear your engine faster or clog a particulate filter. Your vehicle needs both to match.

They're the two main sets of engine oil standards. ACEA, the European Automobile Manufacturers' Association, sets the standards most European vehicles use. Its categories are grouped by letter: A/B for petrol and diesel cars, C for vehicles with exhaust after-treatment, and E for heavy-duty diesels.

API, the American Petroleum Institute, sets standards used mainly by American and Asian manufacturers. Petrol categories start with S, such as API SP, and diesel categories start with C. In the UK and Ireland, most vehicles call for an ACEA specification or a manufacturer approval.

An approval means the vehicle manufacturer has tested the oil and formally listed it against its own standard, such as VW 504 00 or MB-Approval 229.51. A recommendation, often worded as “meets” or “suitable for”, means the oil maker states the oil meets that standard's requirements, without the manufacturer's formal listing.

If your vehicle is under warranty, check your handbook: some manufacturers ask specifically for an approved oil.

Every Duckhams product page lists the oil's grade and the specifications it meets. For full technical detail, download the product data sheet (PDS) from the product page. Safety data sheets (SDS) are available on request through the Technical & Product Support enquiry form. To find the products that meet your vehicle's requirements, enter your registration into Find My Oil.

SAPS stands for sulphated ash, phosphorus and sulphur. These come from additives that protect the engine, but over time they can clog diesel and petrol particulate filters (DPF and GPF) and reduce how well catalytic converters work.

Low-SAPS and mid-SAPS oils limit these additives to protect your exhaust after-treatment while still protecting the engine. Most modern cars with a particulate filter need one, usually an ACEA C-category oil.

OEM stands for original equipment manufacturer, meaning the vehicle maker. An OEM approval is a carmaker's own oil standard, set for its engines and often stricter than ACEA or API. Common examples include VW 504 00 and 507 00, BMW Longlife-04, MB-Approval 229.51, Ford WSS-M2C913-D and Renault RN0720.

If your handbook names an OEM approval, choose an oil that lists that exact code.

Modern engines are smaller, more highly turbocharged and built to meet strict emissions limits. They run hotter, use particulate filters and catalysts that certain additives can damage, and often have longer service intervals.

Many are also designed for thinner oils, such as 0W-20, to cut fuel use, and some use timing belts that run in oil. Each of these puts different demands on the oil, which is why manufacturers set precise standards for their engines.

Yes. Many oils meet several standards at once, such as ACEA C3 alongside VW 504 00/507 00, BMW Longlife-04 and MB-Approval 229.51, which is why a single oil can suit vehicles from several brands. Some standards can't be combined, though. A full-SAPS oil can't also meet a low-SAPS standard, for example. Always check that your vehicle's exact specification appears on the label or product page.

ACEA C oils are designed for vehicles with exhaust after-treatment, such as diesel and petrol particulate filters. They have limited levels of SAPS to protect these systems, so they're often called low-SAPS or mid-SAPS oils.

The categories currently run from C2 to C7. They differ mainly in SAPS level and in high-temperature viscosity, which affects fuel economy. C3 is the most widely used. The numbers aren't a ranking, so use the exact category your manufacturer specifies.

Every few years. ACEA typically revises its standards every two to five years, API introduces a new petrol category roughly every five to ten years, and carmakers add new approvals as they launch new engines.

A new standard doesn't make an older one invalid: your vehicle still needs the specification in its handbook. API categories are generally backward compatible, so a newer one also covers older engines. That isn't always true for ACEA and OEM approvals, so check your handbook or Find My Oil.

Most manufacturers recommend changing your engine oil every 12 months or around 10,000 miles (16,000 km), whichever comes first. Long-life servicing can stretch this to two years or roughly 18,000 miles (30,000 km). If you mostly make short journeys, tow or drive in stop-start traffic, change it sooner.

Your owner's handbook gives the exact interval for your vehicle, or enter your registration into Find My Oil.

Yes. Change the oil filter at every oil change. The old filter holds dirt, metal particles and used oil, which would contaminate fresh oil straight away. A clogged filter can also open its bypass valve, sending unfiltered oil around the engine. Always fit the filter specified for your engine.

Yes, as long as the Duckhams oil meets the same grade and specification as the oil already in your engine. Engine oils that share a grade and specification are compatible, whatever the brand. Add a little at a time, check the dipstick as you go, and don't fill past the maximum mark. Keeping a bottle of the right oil in the car makes topping up easy.

Yes. On short journeys the engine doesn't reach full operating temperature, so moisture and unburnt fuel build up in the oil instead of burning off. This dilutes the oil, uses up its additives faster and can form sludge. On diesels, short trips can also interrupt particulate filter regeneration, which can add fuel to the oil.

If most of your driving is short journeys, follow the Severe service schedule and change your oil more often.

Yes. Oil thickens as it gets colder, so it takes longer to reach the engine's moving parts at start-up, when wear is highest. That's what the first number in a grade such as 5W-30 measures: the lower it is, the better the oil flows from cold. Cold weather also adds condensation, especially on short journeys. Using the grade your manufacturer specifies covers UK and Irish winters.

No. Modern multigrade oils, such as 5W-30, are designed to work all year, flowing well from a cold start and protecting the engine at running temperature. Use the grade your manufacturer specifies in every season. Changing oil with the seasons dates from single-grade oils, which most vehicles no longer use.

Not necessarily. Follow your vehicle's service schedule. If a change is due in the next month or two, though, doing it before winter makes sense: fresh oil flows better from cold, and old oil may already contain moisture and fuel from short trips.

Before winter, also check your oil level, coolant and screenwash.

No, not unless your manufacturer lists a thicker grade for hot conditions. Your engine's cooling system keeps the oil at a steady working temperature, so the weather has much less effect than you might think. A thicker oil than specified flows more slowly at start-up and can reduce efficiency. Some handbooks list an alternative grade for very hot climates or heavy towing; only use one if it's listed.

Yes. Alongside engine oils for cars, vans, motorcycles and classic vehicles, Duckhams makes brake and clutch fluid and 2-stroke motorcycle oils. Find My Oil shows the other fluids your vehicle needs, with the matching Duckhams product where we make one.

Keep oils and fluids sealed in their original containers, upright, somewhere cool and dry, away from direct sunlight, heat and frost, and out of reach of children and pets. Unopened engine oil typically keeps for around five years. Once opened, use it within about a year.

Brake fluid absorbs moisture from the air once opened, so keep the cap tight and use it soon. Never store fluids in drinks bottles, and take used oil to a household recycling centre rather than pouring it down a drain.

Check it at least once a month and before any long journey. Check more often if your vehicle is older, has high mileage or has used oil before. Most engines use a little oil between services, so a gradual drop is normal, but a sudden one isn't. Our Advice page has a step-by-step guide to checking it.

Colour alone isn't a reliable guide. Diesel oil turns black soon after a change, so go by your service schedule.

It can. As oil ages, its additives wear out and contaminants build up, which increases friction inside the engine. The engine then has to work harder, using slightly more fuel. The effect is usually small, but it adds up, particularly in modern engines designed for thinner, fuel-saving oils such as 0W-20. Changing your oil on schedule, with the specified grade, keeps your engine running as efficiently as it was designed to.

If the red oil pressure light comes on while you're driving, pull over as soon as it's safe and switch off the engine. Low oil pressure can seriously damage an engine within minutes. Wait a few minutes, check the oil level and top up if it's low. If the light stays on with the level correct, don't drive on; call a garage or breakdown service.

An amber or yellow oil light usually means the level is low or a service is due. Check the level and top up soon. Your handbook explains your vehicle's warning lights.

Usually, yes. Classic engines were built with wider tolerances, different metals and seal materials, and often flat-tappet camshafts. Many need a thicker mineral oil, such as 20W-50, with higher levels of zinc (ZDDP) to protect the camshaft and followers. Modern low-viscosity oils are designed for tight-tolerance engines and can give a classic engine too little protection. Check your handbook or a marque club for the grade your engine was designed for.

It's not usually the best choice. Many modern synthetic oils are thinner and contain less zinc (ZDDP) than a classic engine needs, which can increase camshaft wear. Their stronger cleaning additives can also loosen old deposits that then block oilways.

Some classic engines that have been rebuilt to modern tolerances can run on a synthetic or semi-synthetic oil. If yours has, follow your engine builder's advice.

Older engines were machined to wider tolerances, so there are bigger gaps between moving parts. A thicker oil, such as 20W-50, fills those gaps and keeps a strong oil film and good oil pressure. Older engines also use materials and seals designed around thicker oils. Using a thinner oil than intended can lead to low oil pressure, more wear and more leaks.

Use a mineral running-in oil, or the oil your engine builder recommends, for the first 500 to 1,000 miles. Running-in oil helps new piston rings bed in and protects new camshafts and followers, which are most vulnerable in the first hours of running.

Change the oil and filter at the end of the running-in period, then switch to the classic grade your engine needs. Always follow your engine builder's instructions, as they know what was fitted.

At least once a year, even if the vehicle has hardly been driven, or every 3,000 miles (5,000 km), whichever comes first. Classic engines often run without modern filtration and spend long periods standing, so the oil collects moisture, fuel and acids over time, not just with mileage. Change the oil and filter before laying the vehicle up for winter, so it doesn't sit for months in used oil.

Yes. In a stored vehicle, the oil in the engine still collects moisture from condensation, and used oil contains acids that can attack bearings over time. Change the oil and filter before storing the vehicle, and again if it's been laid up for more than a year.

Avoid starting the engine for just a few minutes during storage. A short run creates condensation without getting hot enough to clear it, which does more harm than good.

Yes. Classic oils are typically mineral-based and thicker, with higher levels of zinc (ZDDP) to protect flat-tappet camshafts. Their detergent levels are matched to engines designed before modern oil standards, some of which have no full-flow oil filter. Modern oils are designed for tight tolerances, catalytic converters and long service intervals, so their priorities are different. Our Duckhams Classic range is made for older engines.

Usually not, if you're using an oil made for classic engines. A good classic oil already contains the zinc (ZDDP) and other additives older engines need, in the right balance. Adding more can upset that balance and won't improve protection. Additives are mainly used to raise the zinc level of a modern oil, which is better solved by choosing a classic oil in the first place.

Yes. Duckhams is official oil partner to West Surrey Racing (WSR) in the British Touring Car Championship (BTCC) and sponsors Duckhams Yuasa Racing in the Porsche Carrera Cup GB. Racing puts oil under extreme heat and load, and what we learn there informs the development of our road car oils.

No. Racing shows how an oil performs under extreme conditions, but your road car still needs the oil that meets its manufacturer's grade and specification. A race-proven oil that doesn't meet your car's specification isn't the right oil for it. Find My Oil shows every Duckhams oil that meets your car's requirements.

Performance oils are usually fully synthetic and formulated to protect engines at high temperatures and high revs. They resist thinning under heat and shear, keep a stronger oil film between moving parts, and evaporate less, so the engine uses less oil. They're designed for high-performance and turbocharged engines, and for drivers who regularly push their car hard.

Yes, if it meets your car's grade and specification. Performance road oils are designed for everyday use as well as spirited driving. Race-only oils are different: they often don't meet road car specifications, may not be compatible with particulate filters and are designed for short change intervals. Don't use a race-only oil on the road.

Racing engines run at very high revs and temperatures for long periods, and cornering forces throw oil away from the oil pickup. The oil has to keep protecting moving parts, carry heat away and resist breaking down throughout. If it fails, the engine can be damaged in seconds and the race is over. Gearbox and brake fluids face similar extremes.

Often, yes. Racing oils are tailored to a specific engine and championship, and may be thinner or thicker than road oils depending on the engine design. They're built for maximum protection and performance over a short life, usually being changed after each race or event. They don't need to meet road car specifications for long service intervals or exhaust after-treatment.

Yes. Track driving counts as severe use: sustained high revs and temperatures break the oil down much faster than road driving. If you take your car on track regularly, change the oil more often than the standard interval, for example after every few track days, and check the level before and between sessions. Some drivers change it after every track day.

Yes. At high revs and temperatures, more oil evaporates, more gets past the piston rings and more is burned. Hard driving also raises pressure inside the engine, which can push oil vapour through the breather system. Check your oil level before and after a spirited drive or track day, and top up with the correct oil when needed.

Duckhams products are sold through retailers rather than directly by Duckhams: in store at Screwfix across the UK and Ireland and at EG On The Move forecourts in the UK, and online from Amazon, eBay and Screwfix. Our Where to Buy page lists the stores near you.

Duckhams oils and fluids are available in store at Screwfix across the UK and Ireland and at EG On The Move forecourts in the UK, and online from Amazon, eBay and Screwfix. Our Where to Buy page lists the stores near you, and every Find My Oil result links straight to it.

Contact our trade team through the Distributor & Trade enquiry form. Tell us your company name, location, the type of business you run and the products you're interested in, and the right person will be in touch.

Our technical team can help. Contact us through the Technical & Product Support enquiry form with the product name and your question. If it's about a specific vehicle, include the make, model and registration. For quick answers on which oil suits your vehicle, use Find My Oil.

Yes. A product data sheet (PDS) is available for every Duckhams product. Download them from the product page or contact us if you need a sheet that isn't listed.

Yes. Duckhams supplies oils and fluids for cars, vans and light commercial vehicles, in pack sizes suited to fleet maintenance. Our team can help you choose the right products across a mixed fleet. Contact us through the Distributor & Trade enquiry form with the number and types of vehicles you run.

Duckhams products for independent workshops are supplied through our dedicated trade partner. Visit pro.duckhams.com to see the trade range and workshop pack sizes, open a trade account and order. For anything else, contact our trade team through the Distributor & Trade enquiry form.

For distribution, partnerships, sponsorship or other commercial enquiries, contact us through our Contact page and choose the enquiry type that fits, such as Distributor & Trade or Motorsport & Partnerships. Include a short summary of the opportunity and your contact details, and we'll pass it to the right team.