“What oil should I be using in my air-cooled VW?” is a question I wish I had a £1 for every time I saw it asked on forums, Facebook and any other social media platform!

Its one of those classic ‘ask 100 people you’ll get 100 answers’ kinda gigs so we thought we’d do our level best to clear some of the myths and facts around oil, as well as introducing you to a new product to the market which might just make that choice a little bit easier.

Halso have developed a range of multi-grade oils specifically for the VW air cooled engine, to suit all applications from a standard engine, slightly modified or out-and-out performance motor.

So, you may already be wondering why Halso had to specially design an oil for the VW?  



Well, our humble little flat 4 engines are somewhat of an anomaly in the oil market, namely from the fact the Volkswagen is air-cooled. Actually that in itself could be considered a misnomer, as the engine oil itself is responsible for the majority of the cooling efforts. There is no other engine out there where the oil not only acts as the lubricant for all moving parts, but also is responsible for maintaining operating temperatures and allows suspended particulates to collect in the sump, out of harms way. As you can imagine it’s quite a design challenge to accommodate those 3 factors. It is due to this very specific set of criteria that the case of ‘any oil will do’ is very much not the case!


There are a lot of buzz words out there in the market place such as Mineral, Synthetic and Semi Synthetic, which can leave you scratching your head at the best of times! Put simply synthetic oils are chemically derived from uniform molecules and use no paraffin, before being blended with Viscosity Improving Additives (which we will come on to). Generally these are referred to as Group 4 oils, especially for motor vehicle use. However, some Group 3 based oils have been labeled “synthetic” through a legal loophole, which could explain the confusion around this subject.   Synthetic oils do not meet the demands of a standard air-cooled VW engine, as these rely on modern style oil filtration systems and will not suspend particulate matter, with many synthetic oils depending on a water-cooling system for the engine to manage temperature. They also usually work at a much higher operating temperature. Using these oils can lead to bearing issues and premature wear. By contrast, mineral oil has had fewer refining processes carried out from extraction as crude oil.

So, recognising the specific requirements of the air-cooled VW engine Halso have developed 3 specific products to cover all aspects of VW engines. Of these 3 products, 2 of them are considered a conventional, ‘mineral’ oil.

One common factor across the Halso range of oils here, is the Zinc content, or ZDDP (Zinc DiakylDithioPhosphates).

Modern multigrade oils have legally had to reduce the amount of Zinc in them, due to its destructive nature with Catalytic converters, in modern exhaust filtration systems. Zinc plays an important part in attracting and retaining an oil ‘film’ on major bearings and contact surfaces, so is vital in an air-cooled VW.

The ZDDP Levels in the Halso range of VW Air-cooled Motor Oils ranges from 1200 – 1600+ppm.


First up from Halso is the 10w 30 grade for use in standard engines, and this is the product I am currently using in my ’67 1300 single port Beetle.

The beauty of the 10w30 grade is that it is exactly the same viscosity as an SAE 30 grade oil at operating temperature – but the added bonus of the 10w viscosity additive means a much lower 10 grade oil behaviour on start up to get round those oil gallery and protect the main bearing whilst warming up. I personally find this particular product encourages you to allow your VW to warm up properly before beginning your journey, (which you should be doing anyway!)

The next product in the line up is the 15w40 grade mineral oil. The difference here being that this particular oil depends on an external oil filter and cooler , as the property of suspending particulates as found in the 10w30 is now gone. More suited to say a twin carb 1776cc engine with a ‘Fram’ style filter but relatively low RPM ceiling.

Finally the lineup concludes with a semi-synthetic 10w40 grade oil suitable for much higher revving, larger capacity engines such as the 2110cc engines and upwards or anything revving up to 8k RPM.

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So lets talk numbers; what does 10w30, 15w40 and 10w40 mean exactly?

In essence it really is like having your cake and eating it! The best of both worlds, you know what I mean?

There are 2 very different and significant stages of engine operation. First being start up. This is the single most damaging stage of engine life. Especially if your VW has sat for a long period of time, the main bearing faces and oil galleries will be relatively dry, and oil will take a while to reach every crevice, all that time moving parts are wearing away with metal-on-metal contact.

The lower the grade number of oil, the lower the viscosity, right, so picture pouring a bottle of water out, and a bottle of maple syrup at the same time – the water will empty faster with its lower viscosity. Therefore low viscosity oil will whip up round the bearings and galleries much quicker than high viscosity oil. But under full operating temperature, low viscosity oil will not adequately protect your engine. It gives here that the W actually stands for “winter” viscosity or the cold start temperature viscosity.


What Halso have done here is create an additive package to manufacture a multigrade oil which will behave like 10 weight oil on start up, and protect like a regular SAE30 at operating temperature, in the Standard variation of the product.

You may well be thinking “Well, why didn’t Halso make a 5w30 or a 0w30?” Put simply, everything in life is a trade off, and the more Viscosity Improving Additives you add into an oil, the more detrimental effect can be had elsewhere. For example, viscosity additives can lead to a reduced engine oil life, and result in sludge mess if the oil isn’t changed at the regular interval. Issues with a shift in product behaviour have also been noticed in oils with a wide range in viscosity, such as 5w40 for example, as the oil quickly looses its ability to adapt to viscosity change, effectively making it a 5w30 or even 5w20 as it ages.


What Halso have done here is very carefully and cleverly blend and oil to suit each application you could give to your air-cooled VW engine, whilst minimising any drawbacks. Be sure to choose the Halso product that best suits your purpose and even more importantly, change it properly and regularly. HALSO recommends that an oil change is completed every 3,000 miles, as a ‘thinning’ of the oil will be experienced, due mainly to the heat. This apparent thinning of the oil is not the actual base oil losing it’s viscosity, but is mainly due to the fact that the additives (usually around 18-20% of the volume) start to breakdown and lose their effectiveness under high temperatures.

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