During the winter. I regularly carry a Ruike Hornet, but in Florida, March to November, I dress light.Depending on how much wet fuel is actually getting on your knife, it could be at least partially dissolving or mixing with your lubricating oil. You also might be ending up with some level of dust slurry. That would favor washers but personally, I go with a small fixed blade if I could. Do you wear coveralls or a jacket?