Moisture is not a problem as it wont build up enough pressure to matter. It must have been a lot of water, hence I speculate ice. Refineries have he same problem -- it's only a problem in large enough quantities. A bottle of water I doubt would do it. It would be like a tiny ice cube in a fryer.
As for your oil bill. It includes TAXES and you're paying RETAIL. The producer of that heating oil isn't getting $4.00
Naphtha no idea. Maybe it had too much particles in it when they made it with number 6. Maybe they gave away too many samples and that lowered the reported average.
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