Bar oil is one of the two oils your chainsaw needs to work (2-cycle engine oil is the other). Bar oils have a simple task and yet they are commonly not very well understood. What kind of oil is bar oil really? What is its viscosity or SAE grade? Do you have to use a special oil or will any do?
In this article, I will tell you the basics of bar oil. In a nutshell, bar oil is any oil used in a chainsaw to lubricate the contact between the guide bar and chain. The commercially available bar oil products are basic lubricating oils with possibly a few additives for improved stickiness and cold temperature properties. Bar oils have viscosity profiles similar to common SAE engine oils which can serve as substitutes, but rarely give any economic advantage.
Next, we’ll go through all of this in more detail. You may also want to check my overview of bar oil alternatives as well as specific instructions on which engine oils and vegetable oils make the best bar oils.
What is Bar oil?
What do bar oil products really consist of – what kind of oil are they?
The real compositions of these oils are sadly proprietary. But I have been able to deduce quite a few things about them by combining the short product descriptions to datasheet values. In summary, we can assume at least this much:
- Most bar oils consist of a base oil (or oils) and additives
- Base oils are mineral, semi-synthetic or vegetable:
- Most bar oils have a mineral (petroleum) base oil
- Premium bar oils (e.g. Stihl Platinum) are semi-synthetic
- “Biological” or “green” bar oils are vegetable-based
- Additives include at least a tackifier to improve stickiness
- Winter bar oils use a low-viscosity base oil and possibly some additives to keep the oil thin in the cold
- All-season bar oils are both for winter and summer, similar to multi-grade engine oils (e.g. 5W-30). These probably include a viscosity index improver (VII) additive.
What is the purpose of bar oil?
Bar oil has one job: to lower the friction between the chain sliding on the guide bar. By lowering the friction, bar oil achieves many goals:
- Slower wear of the bar rails and the chain
- Lower heat generation in the bar
- Less power lost into chain friction
Bar oil is essential – without it, your saw will have less useful power and you will ruin your bar and chain in no time.
What is the viscosity of bar oil?
Bar oils do not commonly have a specified viscosity or SAE grade. But I was able to come up with reasonable viscosity ranges by digging through the data sheets and doing some comparative research in engine oils.
Summer bar oils typically have a viscosity around 65…200 cSt at 40°C (104°F) and around 10 cSt @ 100°C (212°F). Their viscosity profile is similar to straight-weight SAE 30 engine oil.
The temperatures 40°C and 100°C are the standard for viscosity reporting points for many technical oils. They also nicely span the chainsaw guide bar operating temperatures during summer, giving a good picture of the probable bar oil viscosities in use.
Winter bar oils have lower viscosities of 40…60 cSt at 40°C and 5…7 cSt @ 100°C. This makes them similar to a SAE 0W-16 multigrade engine oil and indicates that viscosity index improver (VII) additives are probably used.
Sadly, winter bar oil viscosity in more realistic winter temperatures is not reported for any winter bar oil product. Judging by the given pour points and SAE 0W…5W behavior, winter bar oils are likely to be at around 5000 cSt at -30°C (-22°F) and remain pumpable to -30°C…-40°C (-22°F…-40°F).
Is bar oil expensive?
Many people are interested in substituting commercial bar oil products with a more affordable generic oil.
While this is often technically possible, it rarely saves you a lot of money. Bar oil is in fact quite cheap, often available at only $10/gal. This means that most engine oils and vegetable oils are actually more expensive.
Only three vegetable oils (canola, soybean and corn) promise substantial savings compared to commercial bar oil – see my bar oil alternatives article for a cost rundown and vegetable bar oil comparison for more info on applicability, temperature ranges and more.
Is bar oil a big cost?
But how much exactly are you going to be spending in bar oil? Is bar oil really a major cost in chainsaw operation?
To answer this, let’s take some numbers. Let’s assume you’re running an mid-range forestry chainsaw (e.g. Husqvarna 372 XP) with the oiler set to 10 ml/min, i.e. midway through the adjustment range. This puts your bar oil consumption at around 20 oz/h, or around 1.3 gallons per day of very intensive sawing.
Using an average-priced bar oil at $12/gal, this rate means you’ll be spending around $2/hour or around $16 per day for bar oil. This is real money.
But consider this: at the same intensive sawing rate you’ll also consume ~½ gal/h of gas. Your gas costs will run anywhere from $3/hour up to $13/hour depending on the type and volumes you are buying – this is $25 to $100 per day.
So while bar oil is a significant cost, your gas costs many times more – not to mention the value of your time, which is still many times more if you saw for a living.
NB: The bar oil and gas consumption rates above are for very intensive use. In typical logging, bucking and limbing, one half of the rates is realistic.
Can you make your own bar oil?
You can easily make you own bar oil. Actually, there is not too much making to it: just use a compatible motor oil or vegetable oil you have at hand (links to my articles). For an overview of the options, see my article on bar oil alternatives.
Most bar oil alternatives lack a tackifier additive included in the commercial products. A tackifier would improve the “stickiness” of the oil and make it more likely to stay on the chain. Sadly, tackifiers do not seem to be available for consumers to buy in small quantities, so this option is hard to realize for now.
