As this is a fuel tank, you need to consider explosion hazards. If I understood you correctly, you plan to place a pressure sensor low in the (underground) tank and have the cable enter the tank near the top. This means the seal will not only need to be tight against fuels, but also against fuel vapor. I don't know where you are, so I don't know which ex-protection codes apply if any. Make sure YOU know which codes are relevant and follow them.
If you use cable ducts, make sure they are compliant with the relevant codes and stand up to a the fuel-ladden atmosphere (organic solvents attack some plastics).
Other ways to solve your problem:
- screw the pressure sensor directly into a socket on the tank (possible product), this is likely impossible in your case as the tank is underground.
- screw a pressure transmitter into a socket at the top of the tank, have the actual sensor hanging at a steel rope into the fluid (possible product)
- Use a different level mesurement technology like radar or ultrasonic that measuers from the top (though that is likely more expensive, but you can maintain the sensor more easily). The beauty of radar is that with some tank materials (not metals obvs.), you can measure through the tank so the whole sensor does not contact your medium, there's one less seal you need to worry about re. explosive vapors and so on.
I would go with option two as a compromise between ease of service and cost. Find a reputable vendor of measuring devices near you and talk to their application engineer.