Synthetic Oil Explained

7/13/14 IMPORTANT UPDATE! Since this article was written, there have been a lot of changes with oils which we use in our beloved vintage aircooled engines. For a long time, one “insider trick” was to use a good diesel oil, like Delo 15-40, which had great anti-scuff properties, even for our gasoline engines. But as things progress, things change! You have to keep up with these changes, or you can pay a serious price. A couple years ago the formulation of diesel oils CHANGED, and they no longer offered the advantages they had previously for us!

At ACN we try to keep abreast of what people at the ground level (that’s you) are experiencing, with all sorts of products. We have been hearing reports of people running diesel oils running oil temperatures that were ~20F elevated from their “normal” temperatures for some time, and finally put 2 and 2 together. On our recommendations that they change from the diesel oil to a good dino oil (for gasoline engines), or synthetic (also for gasoline engines), customers have reported  oil temperatures dropping back to where they were used to seeing them. So as of now (7/15/14) we have had reports of great results with both Amsoil Synthetic Z-Rod 5-30, or Valvoline VR-1 (which we do not sell, but you can get it at your FLAPS). What weight oil to get is another topic entirely. What you need to know is that as of this moment we know these are 2 oils that will work very well on your vintage VW aircooled engine!

Should you run Synthetic Oil in your VW?

Synthetic Oil: Whether it’s evil stuff or good stuff depends on who you talk to. And a lot of what you hear from backyard mechanics is rumor and myth. Myth # 1 is the claim that you don’t have to change Synthetic oil as often as regular motor oil. Remember when Mobil 1 said you could go 25,000 miles between oil changes with synthetic oil? Notice they haven’t said that for a good number of years? Keep that thought on the back burner for now…

Myth #2 is that synthetic oil causes oil leaks. In this article I’m going to try to dispel these myths for you with the cold hard facts about the differences and similarities between dino vs. synthetic oil.

Let’s talk first about what “dino” oil is (Dino is short for Dinosaur, which is when it started forming). Dino oil is created from something called “Base Stock”. Base stock is refined mineral oil that contains no additives. It is the interim product that is reached after crude oil (that comes from the ground) has undergone refinement. From there, additives are combined with the Base Stock, to create our motor oil. There are 7 main additives which include anti-foaming agents, anti-corrosion, etc, etc. At the molecular level, dino oil contains molecules of varying sizes. Imagine the floor of a gymnasium covered with basketballs, baseballs, volleyballs, and beach balls. Now imagine that all those different size “balls” are moving around, flowing past the floor. Every time a ball surface contacts the floor surface, the ball absorbs heat from the floor. That is how oil removes heat from your engine components, from surface to surface contact.

Now imagine the same gymnasium floor covered in uniformly sized golf balls. Smaller, more uniform molecules can absorb more heat from a surface, because there are more of them AND they have a larger surface to volume ratio which means they have more surface area contact. That’s what synthetic oil is. A man-made “Base Stock”, where all the molecules are the same size, and smaller than those in dino oil. Better heat transfer, better lubricating properties, and a lot wider temperature range without breakdown, are now obtained.

Synthetic Oil Myth #1 debunked

Oil does not break down under normal use. This is true of both dino and synthetic oil and is also the reason why you take oil to the Recycling Center and not the trash dump. So if oil itself doesn’t ever degrade, why do we have to change it? The answer is twofold: additives and contamination. It will probably surprise you to learn that synthetic oil has all the same additives that dino oil has! The additives in oil DO break down, which is part of what necessitates oil changes. The other reason for regular oil changes is that with use, motor oil becomes contaminated (dirt, water, acids, etc). Using synthetic oil does not protect against either of these problems, which is why you CANNOT go further between oil changes when running a synthetic. You should still change your synthetic oil at the same intervals as you do with dino oil. Anyone want to guess how many claims Mobil 1 had to pay to people that were going 25,000 miles between changes?

Synthetic Oil Myth #2 debunked

Synthetic oil causing oil leaks is another commonly spread myth. The truth of the matter is that if all your engine seals and gaskets are in good condition, synthetic oil will NOT leak in your engine. The myth started because on occasion, an engine will leak with synthetic oil, but not dino oil. The reason for this is that the smaller molecules of the synthetic are able to get past very small crevices, where the larger molecules of dino oil cannot. But this does not mean that the synthetic oil has caused the leak, it simply has “discovered” an infant leak, and regardless of what oil you are running, this infant leak will eventually grow to a size that will allow dino oil to occupy and pass also. Synthetic oil has not been shown to deteriorate engine seals or gaskets. It is not some evil solvent that will break down sealant, or anything like that. Like was said earlier, it is just a man-made base stock, that is uniform and smaller in molecule size than dino oil. Nothing more, nothing less.

Advantages to Running Synthetic Oil in Aircooled Engines
A lot of people ask “What’s the point of running synthetic oil, if you can’t change it less often?” Here’s the answer in a nutshell.

Since synthetic oil has better heat transfer qualities than dino oil, your internal engine temperatures will be lower. Things like bearings, especially, will not operate at as high of a temperature as a result. The wider range of temperatures that synthetic oil can withstand is well suited for the air-cooled VW engine. With head temperatures normally between 300-350 degrees, synthetic will not breakdown while lubricating the valve train components at the heads. The better lubricating properties of synthetic in general will lead to a longer engine life as well. On average, when synthetic oil is run in an air-cooled VW engine, head temperatures stay the same, but engine oil temps reduce by anywhere from 10 to 15 degrees. This is in identical engines that have all the correct cooling tin in place, and are not suffering from overheating to begin with. Important note: Do not run synthetic to fix a hot running engine. Find the real reason it’s running hot, and fix it!

Another benefit is that since synthetic oil is man-made, it can be tailored to suit a wider range of needs. Synthetic oil is now being made is such weights as 5w50, and 0w30, weights that are not possible to achieve with dino oils.

At Aircooled.Net we recommend that you run synthetic oils in all cases, with one exception: you should continue to run dino oil (and change it every 1k miles) if your car still has the stock oiling system. We carry Amsoil Z-Rod 10W-30 and Z-Rod 20W-50 , we recommend the Z-Rod 10W-30 in most every case, especially if the engine is relatively new.

In transmissions we can not praise synthetics enough; RUN IT, especially if you live somewhere that gets cold (under 30F/0C). Use Amsoil’s 80W-90 Synthetic Gear Lube for most cars, but use Amsoil’s Super-Duty Gear Lube for off road or drag racing cars. Either will allow your transaxle to shift smoothly, even at sub zero temperatures!

There is one thing I need to clarify though — if you are not running an oil filter, there really is no point to using synthetic since your oil is going to become contaminated very quickly. Your engine will still benefit somewhat from it, but due to the higher cost of synthetic oil, the gain of running it before it becomes contaminated is negligible. Oil change intervals range from 1000-3000 miles in the VW engine with a strainer (not a filter). VWoM (Mexico) recommends 1k mile intervals on non-filtered engines; keep this in mind for your pride and joy! But on the flip side, the stock VW engine only takes 2.5 qts anyways, it’s not going to break you if you do want to run synthetic!

Eric Allred, Aircooled.Net Guest Writer

Edited 7/13/14