I will keep an eye on the o-ring thanks. I will check on the size. I have a lot of o-rings and probably several replacements. I will also check the probe for sharp edges. A small bit of lubricant would probably help as well. I am a SCUBA instructor and we have a lot of o-ring seals. very light amounts of silicone grease extends the life. I am not sure if the fuel lubricant should be helping that. If the o-rings are allowed to dry they crack and fail early.

I appreciate all the comments on the filler. I should be able to easily convert this to another format if it does fail.