Keep the bar oil cap sealed for storage

Leave the cap on. Venting the bar oil tank to “let condensation escape” is a solution to a problem that mostly doesn’t exist, and it can invite worse problems.

The real fix is to store the chainsaw with the bar oil tank full. Bar oil doesn’t evaporate or go bad like fuel, so a full tank leaves almost no air space for moisture to hang around in. If you drain it and leave the cap off, you’re giving humid air a direct path inside. Every time the temperature changes, moist air gets in and then condenses on the interior. That’s how you get rust and contaminated oil, not by leaving the cap sealed.

Worried about pressure? Don’t be. Most bar oil caps have a small vent anyway, so the tank can equalize without you touching it. The manufacturers don’t say anything about removing the cap for storage because there’s no need.

Keep it sealed, keep it full, and your bar oil tank will be fine. If you’re concerned about moisture, top off the oil — don’t air out the garage.