It seems like you might be referring to a measurement or a specific term. "3500l CFE" could be interpreted in a few different ways:

1. Volume and Unit: "3500l" typically refers to a volume of 3500 liters. "CFE" could stand for "Centifuel Equivalent," which is a measure of energy content, often used in the context of fuel or energy sources. So, this might refer to 3500 liters of a fuel with a certain energy content.

2. Technical Term: In some technical contexts, "CFE" might refer to a different term or acronym. Without more context, it's hard to be sure.

3. Vehicle or Equipment: Some vehicles or pieces of equipment have fuel tanks or fuel capacities measured in liters, and "CFE" could be a specific feature or capacity related to that equipment.

Could you provide more context or clarify what "3500l CFE" refers to? This will help me give you a more accurate response.