I've had both of those containers for my F-250 diesel truck that holds 15 qts. of oil. I have the 15 qt. round one and the 16 qt. square one. I've had problems with the caps on both. The pour cap that you use to drain the oil from the round one leaked. They sent me several replacement caps. They all leaked too. On the 16 qt. square pan, the vent cap constantly pops open by itself. Poor moldings. I'm going to contact FloTool about that issue too. They need to get their act together.
No problem with overflow though

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