Motorcyclists, especially owners of new motorbikes, often wonder whether they should change the oil before putting their motorcycle into winter storage. The mileage since the last service is only 1,500 km, meaning the oil is still quite fresh. But is it still worth replacing it before a long period of inactivity?
According to most manufacturers, the answer is yes. They recommend changing the oil before storing the motorcycle for the winter. The reason is simple: over time, oil can become mildly corrosive. The sulfur and phosphorus it contains can form acids when they react with combustion byproducts and moisture, which is inevitably present in the air.
Fortunately, engine oils contain additives that neutralize acidity. This characteristic is known as the Total Base Number (TBN). However, TBN gradually decreases over time, even if the motorcycle is not being used. That is why the recommendation to change the oil before long-term storage is based on a simple idea: let the engine go into its “winter hibernation” with the maximum possible reserve of neutralizing additives.
But oil with low mileage should still be fine, right? In the case of our fellow rider, almost certainly yes. However, only a laboratory analysis can confirm this with complete certainty. Without such an analysis, the condition of the oil can be assessed using three key factors.
The most important of these are mileage, humidity, and storage duration, in that order.
Mileage is the most obvious criterion: oil gradually loses its properties during use. Therefore, if you have already reached roughly the midpoint of the service interval, it is wiser to change the oil before winter storage. That way, the engine will remain well protected, and you will have one less thing to worry about in the spring.
Humidity is the second important factor and the main enemy of TBN. If you frequently ride in the rain or live in a damp climate such as Siberia or the northwestern part of European Russia, the oil works harder to maintain its neutralizing capacity. In dry southern regions, it ages more slowly, and this applies both during operation and while the motorcycle is sitting idle.
Storage duration is the third factor. Are you leaving the motorcycle parked for just two or three months until the first signs of spring, or are you leaving the country for a year? TBN is depleted very slowly when the motorcycle is standing on its side stand, but it continues to decline nonetheless.
In the end, yes, it is ideal to store a motorcycle with fresh oil and a full reserve of TBN. However, this is a best-case scenario rather than an absolute rule. Under normal operating conditions, even a three-to-five-month period of inactivity is unlikely to allow microscopic corrosion of internal steel components to become a real problem, there simply is not enough time. Therefore, our advice remains the same: follow the standard oil-change interval based on mileage or replace the oil once a year, exactly as specified in the owner’s manual.