In a previous article we explored alternatives for commercial bar oil products for lubricating the chainsaw guide bar and chain. One of them was engine oil: it’s commonly available, and though not cheap, it has excellent lubrication properties.
But what kind of engine oils work as bar oil? Is a specific SAE grade (weight) needed – SAE 30, 15W-40? How about 2-cycle vs. 4-cycle? I was not able to any answers to these basic questions, so I decided to a bit of comparative research myself.
In this article, I will share my conclusions with you. In summary, both 4-cycle and 2-cycle engine oils can be used as chainsaw bar oil depending on the specific product and season. The common SAE multi-grade oils have the best performance and all-season applicability, while 2-cycle oils must be controlled for the flash and pour points. Engine oils often work well enough, but do not offer an economic advantage over bar oil products.
NB. This article is about using fresh, unused engine oil as bar oil. Used engine oil is a different story – read my earlier article on why not to use it.
Which engine oil types as bar oil?
| ENGINE OILS AS BAR OIL Engine oil type | Applicability | Price |
|---|---|---|
| 4-cycle SAE grades | – multi-grades all-season – single-grades in summer – moderate price | $12…$18/gal |
| 2-cycle, marine/TC-W3 | – viscosity OK – expensive – check flash & pour point | $14…$20/gal |
| 2-cycle, air-cooled/racing | – viscosity OK – very expensive – check flash & pour point | $30…$80/gal |
The table above lists the types of engine oils you can find: the SAE-graded 4-cycle oils for cars and trucks; the 2-cycle TC-W3 oils for water-cooled engines; and the high-performance 2-cycle oils for air-cooled outdoor power equipment.
All of the types can be used as chainsaw bar & chain oil. Below you find a breakdown of which can you use and when.
What SAE weight should bar oil have?
Most 4-cycle automotive engine oils have a SAE grade, often called weight, which tells how viscous the oil is. The table below shows which SAE grades are suited to use as chainsaw bar oil in summer, winter and Arctic conditions; explanations further down.
| ENGINE OILS AS BAR OIL | Season |
|---|---|
| SAE single grades: | |
| 20, 30, 40, 50 | S |
| SAE multi-grades: | |
| 0W -20, -30, -40 | SWA |
| 5W -20, -30, -40 | SWA |
| 10W -20, -30, -40, -50, -60 | SW |
| 15W -40, -50, -60 | SW |
| 20W -40, -50, -60 | S(W) |
| 25W-40 | S |
| S: summer use W: winter use A: Arctic use |
Commercial bar oil products do not have a SAE grade assigned; instead, we’ll do the matching through viscosities at the standard temperature points of 40°C and 100°C.
Summer use
Common SAE single grade engine oils (straight-weights) SAE 20…50 and all common SAE multi-grades are OK for use as bar oil in summer conditions.
Why such wide ranges? The reason is that bar oils vary widely in viscosity, so their engine oil replacements do not have to be too matched either.
An example: a typical commercial bar oil has a viscosity of around 10 cSt at 100°C (212°F) but 150 cSt at 40°C (104°F). The 100°C viscosity is similar to a SAE 30 engine oil, but the viscosity change is larger than with modern engine oils. (Probably caused by tackifiers.)
The 60°C (140°F) temperature swing is something that your bar will easily see in summer service. A more realistic full summer service temperature range would be from a 10°C (50°F) cold start on a cold morning to 90°C (200°F) when milling on a hot day. Between these extremes, the typical bar oil would swing from 15 cSt to 1000 cSt – almost a 100-fold change.
Meanwhile, the SAE engine oil grades have at most a 4x spread in viscosity from SAE 20 (7.2 cSt @ 100°C) to SAE 60 (24 cSt @ 100°C). It is clear that the viscosity swings with temperature are far larger than the differences between engine oil grades.
The viscosity swings with temperature are far larger than the differences between engine oil grades.
Also consider: vegetable-based biological bar oil products like Stihl BioPlus have a much lower viscosity of around 40 cSt at 40°C than the regular, petroleum-based ones. Although bio-oils change their viscosity less with temperature, they’ll probably end below 10 cSt at 100°C.
Conclusion: bar oils vary widely in viscosity and still work, so engine oils in most SAE grades should work too.
Winter use
The best engine oil grades for bar lubrication change slightly in the winter: the lower temperatures mean that we should prefer thinner oils, i.e. lower SAE grade numbers.
In winter use, common multi-grade engine oils work the best as bar oil. Good choices include 0W-20, 5W-20, 0W-30 and 10W-30. In temperate regions, single-grade SAE straight-weights SAE 20 and 30 are probably OK too.
The winter guide bar service temperatures are around 30°C (86°F) lower on average than the summer ones. A range from -20°C (-4°F) to 60°C (140°F) should cover most areas and chainsaw operations.
The biggest hazard with bar oil in the winter is crystallization: it turns the oil stiff or solid, jamming the oil pump and gluing your chain to the bar. To avoid this, you should stay at least 15°F (10°C) above the pour point of the oil.
Fortunately, most common SAE engine oils have pour points at or below those of winter bar oil products: SAE multi-grades, for example, range from -40°C to -60°C (-40°F…-76°F). Special caution is required mainly in Arctic conditions, where the 0W-… and 5W-… grades should be preferred.
2-cycle oil as bar oil
Two-cycle engine oils – the kind you mix to your saw or outboard motor gas – are technically excellent oils and also work as chainsaw bar oil in many cases.
2-cycle oils typically have a viscosity profile similar to SAE 5W-20 to 10W-30 multi-grade 4-cycle engine oils. Comparing to the SAE table above, this means that most 2-cycle oils work as bar oil all season (summer & winter).
One issue with 2-cycle oils is a high pour point: most fall between -25°C and -45°C, preventing use as bar oil in cold winter and Arctic conditions. This is probably due to fewer pour point depressant additives compared to 4-cycle oils. Check the pour point before use in the cold.
An another potential pitfall is low flash point: particularly 2-cycle oils for air-cooled engines may flash from a spark at temperatures as low as 160°F (70°C). To avoid a fire hazard, aim for a flash point of at least 210°F (100°C); in intensive use like milling, prefer 300°F (150°C).
| 2-CYCLE OILS AS BAR OIL | Use as bar oil | Pour point | Flash point |
|---|---|---|---|
| Echo Red Armor | – fire hazard | -42°C | 73°C |
| Husqvarna XP+ | – fire hazard | no info | 99°C |
| Stihl HP | – note pour point | -25°C | 222°C |
| Stihl HP Ultra | – should work | -39°C | 220°C |
Stihl 2-cycle oils HP (High Performance) and HP Ultra have safe reported flash points above 200°C (400°F); Husqvarna XP+ is on the limit with its 210°F (99°C) flash point and 15% VOC content. Echo’s Red Armor and PowerCare’s synthetic blend 2-cycle oils have flash points even lower – I would not recommend them as bar oil.
While the performance is often OK, the biggest downside of 2-cycle oils is that they are usually more expensive than premium bar oils. Air-cooled engine oils like Stihl HP and HP Ultra cost more than $50/gal. For reference, bar oil products cost anywhere from $9 to $20 per gallon.
Engine oil vs. Bar oil: Composition
Let’s still take a look at what makes engine oils different from the bar oils at the level of composition:
Bar oils are mineral, semi-synthetic, fully synthetic or vegetable-based oils with only a few additives – the exact compositions are proprietary but we can deduce this much. Bar oils have a very short service life, and the demands for lubrication performance and stability are fairly low.
Engine oils, on the other hand, are typically much more advanced oils: they are made of more refined, semi-synthetic or fully synthetic base oils and a large number of additives. Engine oils have to perform for hundreds of hours in very tough conditions, and the more refined base and additive stack are needed for this.
Bar oils do have one advantage over engine oils: a tackifier additive. This additive makes the bar oil stickier and reduces oil throw-off at bar tip. It is probably also the factor behind the (abnormally) low viscosity index (VI) of bar oil products.
Precautions for using engine oil as bar oil
Before using any engine oil in your chainsaw bar oiler, always check the following:
- The oil flash point is higher than 210°F (100°C)
- The oil pour point is at least 15°F (10°C) lower than lowest ambient temperature
- The oil is clean and unused
- Increase the oil pump flowrate to compensate for lack of tackifier
Engine oil is overkill
Engine oils are on average technically better than bar oils. They lubricate more reliably, work over a wider temperature range, are better at resisting oxidation, inhibiting corrosion and fouling, and so on.
This means that engine oils work well as bar oil: their performance and stability are equal to or better than that of bar oils. The only thing they lack is a tackifier, but increasing flowrate should compensate for this.
The improved properties comes at a price: engine oils are more expensive than bar oil products on average. As we saw in the bar oil alternatives round-up, engine oils cost from $12 up to $50 or more per gallon, while bar oils fall between $9 and $20 per gallon (both in 1 gal quantity).
So while engine oils usually make for a good bar oil replacement, they will not save you money. For economical bar oil replacements, check my earlier article on vegetable oils. You may also be interested in my other article on bar oil basics.
