The ISO VG viscosity and adhesiveness are not enough to qualify a chain oil. Since the enactment of Article L.541-9-1 of the Environmental Code, the mention “biodegradable” on a container has no value unless it is backed by a verifiable standard.
Choosing a chain oil is therefore based on three pillars: the lubricating base, regulatory compliance, and actual performance on the guide.
Environmental claims on chain oils: what the law requires
Article L.541-9-1 of the Environmental Code prohibits the labeling of a product or packaging with “biodegradable” or “environmentally friendly” unless under very strict conditions. At the European level, Directive (EU) 2024/825 on green claims further strengthens this framework: any environmental claim must be based on specific and verifiable evidence.
In practical terms, a container labeled “bio oil” or “eco-friendly” without reference to a standardized protocol is in violation. Most of the marketing claims present on chain oils sold in garden centers will need to be reformulated or removed.
To verify a product’s compliance, it is useful to choose a chain oil for chainsaws based on the manufacturer’s safety data sheet (SDS), which specifies the lubricating base and the standardized biodegradation results.
Vegetable, synthetic, or mineral base: actual performance on the chain guide
The type of lubricating base determines the behavior of the oil well beyond ecological considerations. Each family has distinct technical characteristics that directly influence the wear of the guide and the chain.
Vegetable-based oils (rapeseed, sunflower)
Vegetable oils have excellent natural adhesiveness. Their film maintains the lubricating layer on the links even at high speeds. The biodegradability of vegetable bases generally exceeds that of other categories, provided that the formulation does not include non-biodegradable additives.
Their main limitation remains sensitivity to oxidation. A vegetable oil stored for more than a few months without suitable antioxidant will resinify. This phenomenon clogs the guide, the sprocket, and the lubrication channel. This issue is the primary cause of negative feedback from users who switch to vegetable oils.
Synthetic oils
Synthetic bases offer superior thermal stability and significantly better oxidation resistance. They are suitable for intensive use or machines stored for long periods between jobs. Their cost per liter remains higher, but the shelf life partially offsets this difference.
Conventional mineral oils
Mineral oils remain the most widely sold by volume, mainly due to their price. Their biodegradability is low, and their release into the environment during use poses a documented problem. In an increasingly stringent regulatory context, they are gradually being excluded from professional specifications, particularly in forestry.
ISO VG viscosity and pump flow rate: the pair not to be neglected
The viscosity of a chain oil is measured according to the ISO VG standard. This choice is not trivial: it conditions the actual flow delivered by the machine’s oil pump.
- A grade that is too high slows down the pump flow, especially in cold weather. The lubrication channel may partially clog, causing localized overheating on the nose of the guide.
- The adjustment of the oil pump flow must be adapted to the grade used. Changing the type of oil without adjusting the flow is akin to altering the lubrication conditions of the chain, with a risk of accelerated wear.
A reliable sign of poor lubrication: the chain turns blue on the drive links, or the guide feels abnormally hot to the touch after a few minutes of cutting. In this case, first check the flow adjustment before changing the product.
Resinification of vegetable oils: prevention and maintenance of the circuit
Resinification is the Achilles’ heel of vegetable-based oils. When the oil oxidizes in the tank or circuit, it forms a sticky varnish that progressively clogs the lubrication channels. This phenomenon accelerates in the case of prolonged storage with a partially filled tank.
To limit this risk, a few practices are essential:
- Clean the lubrication channel and the groove of the guide at each chain sharpening.
- Prefer vegetable oils formulated with anti-resinification additives (mentioned on the SDS or product sheet).
A circuit clogged by resin cannot simply be cleared by changing oil. The guide must be disassembled, the circuit purged, and sometimes the pump filter replaced. The maintenance of the lubrication circuit is as crucial for the longevity of the guide as the choice of oil.
Electric or thermal chainsaw: same chain oil
There is still confusion about the need to use a different oil depending on the type of engine. The lubrication circuit of the chain is independent of the motor: whether thermal or electric, the guide, the chain, and the oil pump operate in the same way.
The only notable difference concerns the operating regime. A professional thermal chainsaw runs longer at full speed, which puts more demand on the lubricating film. For domestic use with an electric machine, a vegetable oil with anti-wear additives covers most needs.
The determining criterion remains compatibility with the machine’s pump. Some manufacturers recommend a specific grade in the user manual. Deviating from this exposes the guide to premature wear, regardless of the chosen lubricating base. Before any purchase, consulting the manufacturer’s manual avoids the most common mistakes.
