High-quality mobile fuel tanks are often made from corrosion-resistant metals (such as aluminum alloys) or food-grade, fuel-compatible plastics. These materials do not react with fuel components—unlike lower-grade metals that might rust or leach substances into the fuel, which would compromise its quality and damage engines. Corrosion resistance also prevents metal particles from mixing with the fuel, avoiding contamination that could clog filters or harm fuel systems.

Mobile fuel tanks are designed to minimize moisture entry, a major cause of fuel degradation. Many feature sealed caps with rubber gaskets that create an airtight seal when closed, blocking rainwater, dew, or humid air from entering the tank. Some advanced models also include breathers or vents with moisture traps—these allow air to flow in and out to equalize pressure but filter out moisture, ensuring only dry air interacts with the fuel. Moisture in fuel can lead to microbial growth that forms sludge, or cause phase separation in ethanol-blended fuels, rendering the fuel unusable.

Oxidation—another threat to fuel quality—is mitigated by limiting fuel exposure to oxygen. Mobile fuel tanks are engineered to have minimal headspace when filled appropriately. Less headspace means less oxygen is present to react with fuel molecules, slowing the oxidation process that produces gums and varnishes. These deposits can stick to fuel lines, injectors, and engine parts, reducing performance and causing wear. Some tanks also use opaque materials or UV-resistant coatings to block sunlight, as UV rays accelerate oxidation and break down fuel additives that preserve quality.

Many mobile fuel tanks include built-in filters or are compatible with external filtration systems. These filters trap dirt, debris, or sediment that might enter the tank during refueling or from the fuel itself, preventing contaminants from circulating and degrading the fuel. Some models also have drain plugs at the bottom, allowing users to remove water or sediment that settles over time—this proactive design helps maintain fuel purity without needing to empty the entire tank.