How to Get the Right Air-Cooled Engine Oil
Oil is the precious liquid that keeps your VW's air-cooled engine working smoothly, and it's important that you're putting the right type of oil in your Volkswagen.
I've done a lot of oil checks, changes, and top-ups in a whole range of different air-cooled VWs and have always used SAE 30 oil, but what does that name mean, and is it always the right type of oil for every engine?
If you're not sure what oil viscosity means, or want to double check that you're using the right oil for your air-cooled engine, then this is the guide for you!
You can use the quick links below to jump straight to the section you're most interested in, or scroll down to read the full article.
• What is an air-cooled engine?
• What types of oil can I use in an air-cooled engine?
• What type of oil does a VW Beetle need?
• What type of oil does a VW T2 Split need?
• What type of oil does a VW T2 Bay need?
• What type of oil does a VW T25 need?
• Do air-cooled engines need different oils for winter and summer?
• Do performance engines need different oil to standard engines?
• What does SAE oil mean?
• What is oil viscosity?
• What is the difference between monograde and multigrade engine oil?
• Explaining the names of common air-cooled engine oils
What is an air-cooled engine?
We'll start with a quick explanation of what an air-cooled engine is, before we explain how oil plays a key role in keeping it running properly.
As the name suggests, air-cooled engines are a type of internal combustion engine which disperse excess heat directly using air, rather than via liquid and a radiator.
To do this, air-cooled engines generally feature a lot of cooling fins, which heat up as the engine does. As these fins have such a large surface area, they’re able to transfer extra heat to the air which flows over them, to prevent the engine becoming too hot and overheating, which can cause serious damage to engine components.
Air-cooled engines differ from water-cooled engines found in later VWs because they don’t include a radiator, coolant reservoir, pipes, or pumps. This means you won't need to worry about topping up coolant levels, but also means you'll need to pay particular attention to the type of engine oil you're using.
What types of oil can I use in an air-cooled engine?
The exact type of oil to use in your air-cooled engine will depend on a few factors, such as the type of engine and the climate that you’ll be driving in.
There are different types of oil available for air-cooled engines here at Just Kampers, and elsewhere, which have different formulas tailored to different engines and temperature ranges.
If you’ve got a stock air-cooled engine in your VW then the best place to look is in your owners’ manual, as Volkswagen have explained the different types of engine oil that they recommend for different driving conditions.
Generally speaking, though, you can’t go wrong with Morris SAE 30 oil, as it’s the correct formula for your VW’s air-cooled engine and has been trusted by generations of classic Volkswagen drivers! If you've got an air-cooled VW T25, though, you'll need a different oil to keep your engine running smoothly.
What type of oil does a VW Beetle need?
Generally speaking, you'll need SAE30 for your air-cooled Beetle engine to keep it running smoothly.
It's all I've ever used when topping up the oil in Jack, the 1956 Oval Beetle that I drive as regularly as I can, and I don't think I've ever filled up a classic VW with anything other than Morris SAE 30! Having said that, it's likely because I've never driven a heavily modified classic, or one with a performance air-cooled engine.
If your Beetle has a lot of modifications which are likely to kick out more heat, then you'll want to look at a different grade of oil which can keep your engine protected at these higher temperatures.
What type of oil does a VW T2 Split need?
Most of the time you'll find SAE 30 oil is ideal for your Split's air-cooled engine.
SAE 30 is great for the stock air-cooled engine in your Splitscreen bus, especially at the range of temperatures you're likely to be driving it in here in the UK. It feels like heavily modified engines are less common in T2 Splits, with a few notable exeptions, but if you do have a performance engine then you're likely to need a different grade of motor oil to keep it running right.
The exact type of oil you'll need for a heavily upgraded engine will depend on exactly what you've done to it, but you can speak to your engine builder (if you haven't already) or chat to the JK Team to work out which grade of oil is right for your Splitscreen.
What type of oil does a VW T2 Bay need?
A good SAE 30 oil is ideal for the standard air-cooled engine in a VW T2 Bay, and will keep it running smoothly.
The fact that SAE 30 is the right oil for your Bay won't be a surprise if you've read our previous two entries for the Beetle and Split, but it's what Volkswagen themselves recommend in their owners manuals and is ideal for the range of temperatures you're likely to be starting and driving your air-cooled VW in here in the UK.
As with every air-cooled engine, though, you may need a different grade of oil if you've got a lot of modifications to your engine to give it more power, since you'll also be creating more heat!
What type of oil does a VW T25 need?
Air-cooled petrol engines in VW T25s work really well with SAE 15W/40 multigrade Mineral oil, which keeps everything running right.
If you find that your petrol T25 runs particularly hot and/or you'll be driving it for long periods in warm weather, then SAE 15W-50 might be a better choice as it helps deal with this extra heat.
Engine swaps and modifications tend to be more common in VW T25s, so you may find that a previous owner has made changes to the air-cooled engine in your T25 which may mean it needs a different type of motor oil. If you're unsure, then get in touch with the JK Team and we'll do our best to help!
Do air-cooled engines need different oils for winter and summer?
Yes, if you’ll be driving your air-cooled VW in particularly hot or cold conditions then you’ll need to look at the type of motor oil you’re using, to make sure that your engine keeps running smoothly.
In the UK you’ll usually be fine running your air-cooled engine on SAE30 oil for most of the year, but you should look at changing the engine oil if you’re planning to drive your air-cooled VW through the winter months.
SAE30 oil is seen as the standard oil for unmodified air-cooled engines in most classic VWs, and is ideal for driving through the spring, summer, and autumn, when our air-cooled Volkswagens are driven the most.
However, for driving in the winter you’ll likely find that SAE30 is too thick, or too viscous, to flow smoothly through your engine in low temperatures. Our classic VWs are very capable of handling the snow and ice we often see on the roads over the winter, but you’ll need to make sure you’re not harming your engine with the wrong grade of oil.
There’s an explanation of what oil viscosity means for keeping your engine healthy later in this article.
In the owners’ manuals which came with classic VWs, Volkswagen recommends SAE 20W oil if you’ll be driving in temperatures between 0ºC and 30ºC, or even SAE 10W for temperatures which are consistently below 0ºC.
It’s unlikely you’ll regularly be driving your VW in temperatures below -25ºC unless you're following in the footsteps of the famous Red Terror, but Volkswagen recommends SAE 5W in environments that cold!
Do Performance Engines Need Different Oil to Standard Engines?
A lot of us will use different oil in modified or performance air-cooled engines than we would in a stock engine, to help handle the additional heat that a modified engine produces.
A standard, unmodified air-cooled engine will generate a manageable amount of heat while it’s running, and so is generally fine running on ‘standard’ SAE 30 oil.
If you’ll be driving a lot in hot weather, then Morris’ SAE 20W-50 oil could be a better choice for you as it’s a multigrade oil which performs differently based on the temperature while driving your VW. We explain the difference between monograde and multigrade engine oil further on in this article.
On the other hand, performance or upgraded engines will produce more heat as well as more power and may need specialist engine oil to keep them running smoothly.
Our friends at EvaResto have developed a range of specialist engine oils using their experience with modified air-cooled engines. The formula of these oils has been designed to offer great performance and protection for different engines, including:
EvaResto 15w-40 Engine Oil
This 15W-40 multigrade oil is ideal for modified VW engines which are mostly still stock but run a few performance upgrades. It’s got a higher ZDDP content than their standard 10W-30 oil, to help better protect your engine’s essential components.
EvaResto 10w-30 Engine Oil
Designed to deal with high pressure and high heat production, this semi-synthetic oil holds its own in an air-cooled engine with increased compression, high flow, high pressure oil systems, high lift camshafts, uprated dual or single valve springs, and even turbochargers.
What Do These Oil Terms Mean?
We’ve used a lot of different terms while talking about engine oil, but you may not be totally sure what each of them means.
Luckily, we’ve put together this handy guide to different terms and phrases surrounding engine oil, to help you make sense of the advice we’ve given and find the right oil for your VW.
What does SAE oil mean?
When talking about motor oil, SAE stands for the Society of Automotive Engineers and having 'SAE' on oil indicates that it meets the standards for oil viscosity set by the Society.
Having these set standards in place helps ensure clear communication around how different types of motor oil perform, so that you can find the correct oil for your engine and the temperature ranges you’ll be driving in.
What is oil viscosity?
The viscosity of any liquid refers to its internal resistance to flow, which is sometimes described as its thickness. More viscous liquids like honey will flow more slowly, while liquids with a lower viscosity, like water, will flow more freely.
However, the viscosity of a liquid will change depending on the surrounding temperature. We just said that water is free flowing and has a low viscosity, but it doesn’t flow at all when it’s frozen! The same is true for engine oil, which will flow much more slowly in cold temperatures and take longer to circulate around your engine and protect vital components, until the engine heats up and allows the oil to flow more freely.
This is why the SAE ratings for oil are so important, as they allow you to gauge which types of engine oil are correct for your engine and the environments you’ll be driving in.
What’s the difference between monograde and multigrade oil?
The key difference between these two types of engine oil is that monograde oils are designed to protect your engine while it’s operating steadily at a warmer temperature, while multigrade oil has been formulated to work at a wider range of temperatures.
Monograde engine oils like SAE 30 are ideal for the air-cooled engines in our classic VWs. The oil, like the engines themselves, have been designed to work effectively at a steady rate at a steady temperature.
You can tell an oil is a monograde oil if it only has one number in the name, for example Morris SAE 30.
Multigrade oils also work in air-cooled engines, but have been designed to help protect your engine when starting it up and driving in colder temperatures, and then to keep it running smoothly when it’s up to temperature.
It's easy to spot multigrade oils as they've got two numbers in their name, the first being their viscosity at lower temperatures and the second number being the viscosity at higher temperatures. For example, Morris 20W-50.
Explaining the names of common air-cooled engine oils
We've explained a lot of different terms that you'll encounter when shopping for the oil your air-cooled engine needs, but there are still a lot of acronyms and vaguely mysterious numbers in the actual names of different types of oil you can buy which can be confusing at first glance.
Let's take a look at a few of the most popular types of engine oil we stock for air-cooled engines and break their names down into parts so they're easier to understand.
Morris: Morris Lubricants are a trusted producer of a whole range of different oils, with a great reputation. A lot people will always gravitate to Morris oils as they're a household name for classic car owners.
SAE: Shows that oil has been made to match the SAE standards.
30: This is the viscosity of the oil, and is rated for around 5ºC to 40ºC.
Golden Film: This is a range of engine oils from Morris which have been designed for use in classic cars and vintage engines.
SAE: Shows that oil has been made to match the SAE standards.
Since the oil has a dash (-) or slash (/) in the name (20w-50), we know it’s a multigrade oil, which has been designed to flow easily when its cold or thicker at higher operating temperatures.
20W: This is the viscosity of the oil when cold, and the W at the end shows that it’s an oil which has been designed for winter. 20W oil is generally good for starting your air-cooled engine in temperatures as low as -10°C.
-50: This is the oil's viscosity when it's at your engine's normal running temperature. Oil with a viscosity of 50 will keep your engine running smoothly while driving in temperatures of up to about and 40°C, which is plenty in the UK.
EvaResto: EvaResto are classic Volkswagen specialists, who have designed their own range of engine oils to help keep performance engines running smoothly.
Since the oil has a dash (-) or slash (/) in the name (10w-40), we know it’s a multigrade oil, which has been designed to flow easily when its cold or thicker at higher operating temperatures.
10W: This shows the lower end of the multigrade oil's temperature rating, with the W letting us know the oil is designed for cold starts in the winter. 10W oil is rated to about -25°C, which isn't far off the coldest temperature recorded in the UK!
40: This second number is the viscosity rating when the engine is at normal running temperature, and shows that it's rated for driving in temperatures of up to around 40ºC.
