Got a question about Castrol MAGNATEC or engine oil in general? Please see the answers below.

Engine oil basics

1.What is viscosity and what is the difference between monograde and multigrade?
In order for motor oil to perform its major function - lubrication - its viscosity (in measures of its thickness or resistance to flow) must be capable of holding up under extreme temperature conditions.
Oil thins when heated and thickens when cooled. A grading system like this is used: "XXW-XX", with the first part eg. "10W" indicating the oil's viscous characteristics at cold temperature and the second part eg. "40" indicating those at operating temperature. Oils which only display a single viscosity grade 30, 40, or 50 are known as a monograde.
Monogrades must be replaced seasonally (winter and summer) to ensure appropriate viscosity, therefore the majority of engine oils are multigrade.
2.What is the API service rating?
The API (American Petroleum Institute) Service rating is an American based, two-letter classification that identifies the performance level of the motor oil and the year model of vehicle which it is suited for.
The current API SM classification was adopted in 2004. If an owner's manual calls for API SJ or SL oil, API SM oil will provide superior protection.
3.What is the ACEA classification?
It is a European-based grading system to classify the quality and performance properties of engine oil. Oils are divided into the following two categories:
  • Gasoline & Diesel Engine Oil (Ax Bx category).
  • Gasoline & Diesel Oil with exhaust treatment device (Cx category).
4.What do engine oils do?
  • As a lubricant they reduce the friction and wear that occurs when engine parts move against each other, for example between the cylinder walls and piston rings, or the camshaft lobes and followers/lifters.
  • As a coolant they absorb and transfer the heat produced in the engine combustion chambers and piston undercrown area, cooling the engine and helping prevent overheating.
  • As a sealant they seal the space between the piston ring and the cylinder wall to prevent combustion pressure (engine power) from escaping.
  • As a detergent they prevent waste matter resulting from combustion and impurities from sticking to the engine interior, helping to keep it clean.
  • As a rust inhibitor they neutralise acids produced by combustion gases, preventing rusting and corrosion.
5.What is the difference between synthetic oil and mineral oil?
Mineral and synthetic based oils are mostly derived from crude oil or its refined components. Mineral base oils are produced during normal crude oil refining process and are enhanced with chemical additives. Some synthetic base oils are produced by further refining and chemically altering these mineral base oils. Other types of synthetic base oils are made by using special refinery products to tailor-make specific and unique molecules.
6.What are the advantages of using synthetic engine oils?
Synthetic engine oils are able to:
  • Operate at much higher temperatures for longer.
  • Resist oxidation better than mineral oils leading to less wear and longer engine life.
  • Be used for longer or extended drain intervals.
  • Provide quicker oil circulation at start-up which contributes to improved fuel economy due to less energy being wasted through viscous drag.


1.How is Castrol MAGNATEC STOP-START different from current Castrol MAGNATEC?
Castrol MAGNATEC is targeted at warm-up wear. New Castrol MAGNATEC STOP-START extends the successful Castrol MAGNATEC protection story to stop-start wear, with specially boosted formulations and superior protection demonstrated in stop-start wear testing.
2.How unique is Castrol MAGNATEC?
Castrol MAGNATEC intelligent molecules can cling to your engine. The unique formulations are exclusive to Castrol, and can't be bought from other providers. We carry out extensive testing as part of our product development, and the unique formulations we create are not available to anyone else.
3.What are ultra-refined molecules and what is the technical benefit of them?
The use of ultra-refined molecules represents an improvement in the purity of the raw materials Castrol chooses to use in making MAGNATEC. The technical benefit remains the same – dramatically reduced engine wear during warm-up. As a technology leader, Castrol strives to maintain its position using the most up to date components and raw materials. In the case of Castrol MAGNATEC we have done this by pioneering the use of ultra-refined molecules.
4.What is the right grade of Castrol MAGNATEC for my car?
Castrol MAGNATEC is available in fully synthetic 5W-30, or part-synthetic 10W-40 and 15W-40 grades. Different vehicles require different specifications and viscosity grades. Please visit your country site on the Castrol website and use our oil selector tool to find the right oil for your car.
5.Is Castrol MAGNATEC OK for diesel cars?
All grades of Castrol MAGNATEC are qualified for diesel as well as petrol cars, however to get the most from your diesel car you should rely on the dedicated diesel technology in Castrol MAGNATEC Diesel.
6.Is Castrol MAGNATEC Synthetic or Part-Synthetic?
Castrol MAGNATEC 5W-30 A1 and Castrol MAGNATEC Diesel 5W-40 A3/B4 are fully synthetic formulations providing quicker circulation at extremely cold temperatures and superior performance at high operating temperatures.
Castrol MAGNATEC 10W-40 and 15W-40 are both part-synthetic. All grades of Castrol MAGNATEC contain Intelligent Molecules that cling to critical engine parts to instantly protect from the moment you turn the key.
7.Can I extend the oil drain interval by using Castrol MAGNATEC?
Castrol MAGNATEC is designed to keep your car at its peak throughout the entire length of your car's standard drain interval. We recommend you stick to the service interval as documented in the manufacturer's vehicle handbook.
8.Can Castrol MAGNATEC be used in older engines?
Yes, there is no age or mileage restriction for using Castrol MAGNATEC. Both older cars and new cars benefit in the same way from the protection offered. In older cars where oil consumption is particularly high, you may benefit from using a higher viscosity oil such as MAGNATEC 15W-40. If possible, refer to your vehicle handbook for viscosity recommendations.
9.Can I use Castrol MAGNATEC in my motorcycle?
We would not recommend using Castrol MAGNATEC in your bike. Castrol have a specialist range of Motorcycle oils engineered with Trizone Technology™ which offer unbeatable protection of your bike's, engine, gearbox and clutch.
Visit the Castrol Moto website for more information.
10.Will Castrol MAGNATEC mix with the oil I am currently using?
Castrol MAGNATEC is designed to mix completely with other synthetic, part-synthetic or mineral lubricants. Not only is it perfectly okay to top up your vehicle with Castrol MAGNATEC, you will begin to benefit straight away from the protection of its Intelligent Molecules which reduce the engine wear that would occur with inferior oils. To reap the full benefits of Castrol MAGNATEC, a complete change of oil is recommended.
11.What exactly is stop-start wear – how does it impact the engine?
Stop-start wear, or busy driving wear, is the additional damage to engine parts that comes from the stopping, idling and starting off again that happens during busy driving. Castrol calls these the three critical stages of stop-start wear. Busy driving causes additional microscopic wear on critical parts, and the more busy driving people do, the more wear occurs.
12.Why are short trips and stop/start city style driving harmful to my car's engine?
Almost all engines need up to 20 minutes of operation for the lubricant to reach optimum operating temperature
Harmful by-products (e.g. water and unburnt fuel) can lead to severe damage of the lubricant and the engine. They can also lead to the creation of sludge. The quality base oils and additive systems of Castrol engine oils minimise the effects of harmful by-products and in turn, reduce and improve cleanliness and life.
13.Where can I buy Castrol MAGNATEC?
Please visit your country site on the Castrol website to find your nearest stockist.


1.What is the ‘Castrol MAGNATEC STOP-START Index’ – How does it work?
The ‘Castrol MAGNATEC STOP-START Index’ is a tool developed by Castrol with Sat-Nav leader TomTom that you and your customers can use to highlight their need for new Castrol MAGNATEC STOP-START – by using live tracking GPS data to track the amount of stop-starts normal drivers make in 25 markets a total of 50 cities and regions across the world.
2.What has changed with today’s driving?
More people live in cities than ever before, and these cities are supported by a vast network of roads. We rely on these very roads to take our kids to school, get to work, go for dinner, attend a game, pick up groceries, and finally return home. But with increasingly busy traffic, driving has now more stopping and starting than ever before. On every single trip we make, we encounter situations on the road that make us stop, wait, and start again. Research shows that even a normal driver makes an astonishing 360 stop-starts per week! That is as many as 18000 stop-starts per year, causing damaging engine wear.
3.How is Castrol MAGNATEC STOP-START Index calculated?
The Castrol MAGNATEC STOP-START Index uses data shared anonymously by millions of TomTom navigation users around the world. Drivers in many metropolitan areas around the globe have contributed trillions of anonymous GPS based measurements on an opt-in basis. With millions of TomTom GPS navigation devices already in use, and growing every day, the historical traffic information collected in this way gives valuable insight into the traffic situation on the road network throughout the day.
Using a specially devised algorithm, we are able to calculate the number of stops and starts encountered during a trip. By applying this calculation to thousands of users and journeys, we can accurately measure the stop-start average per kilometer within defined city limits. By simply multiplying this number by the average distance driven per a year, we get the final Castrol MAGNATEC STOP-START Index.