I've noticed a dark, oily puddle under my car after it's been parked. The oil level on the dipstick seems to be decreasing.

Replace the fuel filter to ensure clean fuel is reaching the engine and sending unit.

If fuel contamination is suspected, drain the fuel tank and clean out any sediment or debris.

If the fuel gauge is determined to be the faulty component, the entire instrument cluster may need to be replaced.

Perform diagnostic tests on the instrument cluster to verify the functionality of the fuel gauge. This may involve applying known voltage signals.

Repair any damaged sections of the wiring or replace the affected harness if necessary.

Inspect the wiring harness connected to the fuel sending unit and the instrument cluster for any breaks, corrosion, or loose connections.

If the sending unit is found to be faulty, replace it with a new, compatible unit.

Access the fuel tank and visually inspect the fuel sending unit for any signs of damage or corrosion. Test its resistance values.

Have the fuel injectors professionally cleaned and tested for optimal performance.

Add a quality fuel injector cleaner to the fuel tank to help dissolve deposits.