Have you recently changed the oil. If you overfill the oil you may get some leakage. Also, as someone stated, it could be WD40 if you used a lot of it or it could be condensation or other moisture such as a full waste tank where your float switch didn't work properly and allowed water to get sucked into the blower.
I called prochem today.
It was most likely from a plugged air vent that I cleaned in the picture out had a stone style filter in the cap . They said that was the best thing to do was to clean the vent plug filter because it can build pressure and seep through the se seal.
I'm going to watch it for a while and the sight glass level and well.
It was not WD 40 or condensation of any kind . These tuthil blowers are more critical to maintain than my #4 I had that never had one issue in 25 years .
Thought I would share this with owners of these blowers that the blower vent plug needs to be cleaned quit often unlike #4 blower .
The plug could have got partial pluged from the shop filling the blower up to the top of the sight glass . Its 3/4 to half now and un pluged .
The manual states never over fill it because Iit will over heat the blower and keep the oil level at only half way its very critical aand important it emphasizes .
The filter seemed to have a shalic coating on it but its clean and free flowing now .
The granade comment seems to be out of place .