Engine Oil For Beetles

For me, oil changes used to be something that happened at the garage when I took a car in for service. Why, how, and what oil was used was none of my concern. Given that the whole point of the Beetle is that I want to maintain it myself, I had some learning to do. Before you read on please note that what follows are my own conclusions based one what I found out. I wrote it down to help me make a decision and so that I can refer back to it at a later date when I've forgotten why I made it. I'm making no promises that I've come to the right decision so don't come hammering on my door if you decide to apply my thinking to your own car and it turns out I got it all wrong okay?

As far as a 'modern' car is concerned you can look in the owner manual, a Haynes manual, or ask a retailer and get the same answer; although the retailers will of course want to sell you whatever brand they happen to stock (but we'll return to the the subject of brands later). With an old car like a Beetle it seems that everybody has a different opinion. For starters, the owner manual will be at least 30 years old and quite a bit has changed since then. The main problem however is that most folks are just not used to dealing with vehicles that are more than 10 or 20 years old. For example, I asked the guy I bought mine from what oil he was using and he didn't know because the garage put it in at the last service. He assured me however that it was being done properly as the car had a 'new' engine 7000 miles ago and he showed me the guarantee/service booklet which showed that it had an oil change at 500, another at 5000, and was due another at 10000. Now you don't have to read much about Beetles to know that everybody, but EVERYBODY, says that they should have the oil changed every 3000 miles. Clearly neither the previous owner nor the garage he was using knew much about Beetles.

Incidentally, while we're on the subject of "how ofen?", as I've come to understand it, the reason for this increased frequency (apparently 3000 miles was failrly standard for most cars before the development of modern lubricants and filters) is that: a) the oil plays a bigger part in cooling a bugs air-cooled engine than it does in a water-cooled engine and 'wears out' faster and b) the bug has an oil strainer as opposed to the type of filter that you get in more modern cars and it's better for this to be removed and cleaned out more regularly.

Thus I began to ask around (a lot) and although at first it seemed that everybody had a different answer I eventually saw that they fell into three groups regarding the specification of the oil.

The first group, and these are generally people who are into Beetles, suggest SAE 30 mono-grade. This seems to be largely because VW originally specified SAE 30 for "general driving" but my research indicates that VW said this at a time when multi-grade oils (recommended for pretty much every modern engine) were in their infancy and (apparently) not very good. However, when you consider that some of the guys who swear by mono-grade have been running their dubs for donkeys years then you have to wonder if they might have a point. It also occurred to me however, that for many people, their bug is a summertime play thing that'll rarely suffer the indignity of being rained on never mind being used to haul groceries back from Tesco in the depths of winter.

The reason that climate and season are important is because an engine oil needs to be 'runny' enough to be pumped through the system when the engine is cold and 'sticky' enough to adhere to the parts when it's hot. The two extremes occur when you're starting up on a cold winter's morning and when you're on a long journey on a hot summer's day; so how cold it gets in winter and how hot it gets in summer in the climate where the engine is being run are factors in choosing engine oil.

This is why VW specified SAE 30 for "general driving" because they also suggested other 'weights' for hot and cold climates. In fact in the days when mono-grade oils were standard it was fairly common practice to use one grade in the summer and another in the winter. The engine oil FAQ over at Morris Lubricants says that "it used to be the practice to put a thin monograde, such as a SAE 30, in the engine during the winter and a heavier monograde, such as a SAE 50". So I guess SAE 30 should be just fine for use in the UK.

The second group of people you will encounter suggest the use of a multi-grade oil. Multi-grade oils are specified with two numbers e.g. SAE 10w/40 (the w means "winter") and what it means is that the oil behaves like a 10 weight oil at the cold temperature and like a 40 weight oil would at the hot temperature. Aparently they define 'cold' as 0° Fahrenheit (-18°C), while 'hot' is 212° Fahrenheit (100°C). "They", just in case you are wondering are the Society of Automotive Engineers which is what the "SAE" bit means.

Now this is where it starts to look really complicated because what you need to do is to figure out which of the myriad variations are right for your engine and climate. Life would be a lot simpler if a single product covered the whole range however it seems that multi-grade oils are made possible by the addition of polymers and to get a range that would suit all possibilities you'd end up with more polymers than oil (and it's the oil that does the actual lubricating).

Just about the best way to get yourself really confused is to ask or look on the Internet because you'll be asking people from lots of different climates so what is right for them will not necessarly be right for you (something that may or may not occur to them when they answer). It's also important to realise that even if you ask around UK forums, not everybody will be wise to the need to consider climate and may well have based their own decision upon information gleaned from inappropriate sources. (See my previous post about tyre pressures for an illustration of people on forums thinking they know their stuff when in fact they don't.)

The good news for those of us in the UK however is that we don't have to deal with the really hot or really cold weather. The lower figure stated for a multi-grade will be 0, 5, 10, 15 or 20 but when you consider that this figure describes the viscocity at -18°C it's probably not something that we need worry about too much here in the UK. The higher figure on the multi-grade spec is generally 30, 40 or 50 and again, here in the UK it's not something that we need to worry about as much as somebody in the Mediterranean.

Having said that, we still have to use something and rather than just closing my eyes and reaching towards the shelf I made the following observations:

Rick Higgins of Bug Me Video (as you already know I'm something of a fan and have a high regard for his opinion) generally reaches for a can of 20w/50 but he's in Florida and as he said when I got the opportunity to ask him: "20w50 works good here since it is never very cold and real hot in the afternoon". He suggested that "In the heat of summer in UK you could likely use 20w50 there." He didn't comment on the UK winter and I didn't feel inclined to press him as he'd already said that "I am not really an authority on oil so what I can share is just my experience and what I have learned from others", but the implcation is clear that something thinner may be more appropriate in the winter.

My Haynes manual also suggests 20w/50 but makes no mention of climate and although it's printed on the UK the nice picture of a left hand drive Beetle on the front cover makes me wonder. VWHeritage, Volkspares, Halfords and a number of other suppliers in whom I have some faith suggest 15w/40 and from what I've seen the 15w/40 will be better at lower temperatures than the 20w/50 making this sound like the answer to my needs. However the 15w/40 is generally to be found sitting on the shelf right next to the 10w/40 which presumably would be even better?

In his "Rap On Oil" in "How To Keep Your Volkswagen Alive", John Muir says that "the multi-grade oil's ability to lubricate is not as good as the mono-grade oil's ability at the high temperatures at which an air-cooled engine runs." Rick Higgins also told me that "I like to stay as thick (sticky) as reasonable so the cylinders retain some lube after the motor is shut down." In both cases they're talking about the behaviour of the oil when hot i.e. the difference between the 40 and the 50 bit of the spec as opposed to the 10, 15, or 20 bit.

John Muir is actually an advocate of SAE 30 and also states a strong bias towards the Castrol brand when he says that it "lays a load on my back to carry my own oil wherever I go because this oil is found only in racing and hotrod stores" This raises the question of availability and I figure, given that our mild UK climate appears to give me some flexibility on the weight of the oil, it probably makes sense to consider some of the other factors before I opt for something that's a swine to get hold of for the sake of what may well be a negligible difference in oil's weight.


If the weight of the oil is the most confusing issue, then the brand name is surely the most controversial with those who believe that the well know brands are a rip off facing off against those who believe that you get what you pay for (and arguing amongst themselves about which of those name brands is the best).

The argument in favour of the well know brands is that you're paying extra for the superior quality of the addititives that they put in to make the oil do its job better. Of course you're also going to be paying more for the name but consider this: it's a name they want to protect so they're unlikely to use it to sell product that would get them a bad reputation are they? We'll discuss a few of those additives in a minute but as far as the brand name versus cheap stuff debate is concerned, the bottom line for me is that the price difference generally works out to be less than five quid on the cost of an oil change. Given the amount that I anticipate spending on petrol and other car related expenses I figure that if I can't afford an extra twenty quid a year to err on the side of caution I ought to sell the car and get a bus pass.

As for which brand then: John Muir has (as we've already seen) a very strong bias towards Castrol. Rick Higgins also told me that he "started using Castrol when I had a friend that worked on these million dollar racing boats here. He said that the Castrol would handle whatever beating they gave it and he swore by it."

Other things that we need to condsider are the differences between mineral oils and those with synthetics, and the difference between oils with and without detergents.

When I asked around, the consensus of opinion was that bug engines are better running on mineral oils but very few people had any idea why and even when an explanation was offered it didn't always make a much sense. Along the way it was suggested that the whole point of synthetics was to make the oil keep working for longer but as you should change a bug's oil every 3000 miles (because of the filter if not the oil itself), then there isn't a whole lot of point paying extra for a longer lasting oil. I've also been told that the heat transfer characteristics of mineral and synthetic oils are different and the bug engine, with it's increased reliance on the oil for cooling, needs mineral oil.

Regarding detergents, John Muir says that the VW community was originally dubious about detergents but now favours them. The point of the detergents is that help keep the engine clean by carrying the 'soot' in suspension. If you use an oil with detergents then the old thinking about brown oil being due for a change whereas black oil needs changing, goes right out the window because the oil will go black due to the soot long before it's in desperate need of a change.

The argument against detergents is that the oil strainer in the bug isn't good enough to filer out all the small particles of crud that get cleaned out of the engine. Thus they will circulate causing damage. I don't like the sound of that however the other side of the coin i.e. if the detergents are not putting that crud into suspension, is that they stay stuck in the engine. Is that really a better option?

From what I've learned I think the most important thing about detergents is probably that you shouldn't suddenly switch from non-detergent to detergent oil. In his book John Muir tells of an occasion when he bought a bus from a guy who had been running on non-detergent oil so he had to stick with it until the next engine rebuild. Had he changed suddently, the detergents would have immediately set about cleaning up what was probably a relatively dirty engine thus putting a whole heap of crud into suspension all at once.

Given that my engine is only 7000 miles since the last rebuild I figure that I'm probably safe to use detergent even though the previous owner couldn't tell me what was in there.


Now, I did say way back at the start that the folks I asked fell into three groups and thus far I've only covered two. That's because the third groups are the ones who will direct you to this weeks special offer or whatever they happen to stock. If they are way too cocky and you're in the mood for listening to some bullshit, try asking them how often you should change it and use some of the information given above to see how long they're prepared to carry on talking through their arses before they finally admit that they haven't a clue; otherwise just feel sorry for them for having such a crap job and walk away.


So what did I buy? Well, availability had quite a lot to do with it but by the time I started checking out what I could get my hands on without too much trouble I'd concluded that I wanted a name brand multi-grade mineral oil but I was still wavering between 15w/40 (because of the 15w bit) and 20w/50 (because of the 50 bit).

The local garage (5 mins walk) have Castol GTX High Mileage 15w40 (£16.96/4l) and Duckhams Q Classic Engine Oil 20w50 (£10.99/4.5l). VWHeritage (somebody I can see myself ordering stuff from on a fairly regular basis) have VW Quantum 15w/40 (£16.95/5l) but as it'd have to be posted, and they calculate postage according to order value, I'd have to add a couple of quid onto the cost of that for postage. The only VW specialist within reasonable travelling distance is GSF - who sell Fuchs Titan HD 15w40 (£11.95/5l) - but they're in a town that I rarely visit and I'd have to go past Halfords and my local garage to get there. The Halford's candidate were Halfords own brand 15w/40 Enhanced Mineral Oil (£12.99/5l) or the Castrol GTX High Mileage 15w40 (£16.99/5l).

In the end I went for the Duckhams Q 20w50 for three reasons:

1. I like to support local businesses where I can (use them or lose them). I already buy my petrol from the guy around the corner even though I could get it a couple of pence a litre cheaper if I went to the one 5 miles away. I figure that if I don't I'll have no right to complain if he shuts down and I'm forced to travel 5 miles for petrol. Thus I wanted to buy from him if he had something suitable.

2. I decided in the end that I was more concened about the oil's performance when it's hot that when it's cold. Health problems mean that I'm forced to sponge off the state rather than work for a living so I'm never obliged to go out when the weather is bad. I decided therefore to go for a 20w50 as opposed to a 15w40. I will however be monitoring it when the weather gets cold and if it starts to look a bit thick, I'll let you know.

3. The Duckhams Oil is a pretty green colour like my car. Only kidding. ;-)


So there we have it, Duckhams Q 20w50 is my oil of choice but as I said at the start, these are my conclusions based on what I found out and I make no promises about them. If you want to read more then check out http://www.carbibles.com/engineoil_bible.html which was one of the more comprehensive documents that I found on the subject of car engine oil, while perhaps the best (my opinion again) summarisation of oil issues relating to VW Beetles that I found was in the Vehicle & Part Information section at VW Heritage.