What are fuel tanks made of?
There are two main materials, plastic (high-density polyethylene, or HDPE) fuel tanks and metal (steel or aluminum) fuel tanks.
- Plastic high-density polyethylene (HDPE) fuel tanks are made by blow molding. Blow-molded HDPE can take complex shapes, for instance allowing the tank to be mounted directly over the rear axle, saving space and improving crash safety. Initially, there were concerns over the low fracture toughness of HDPE, when compared to steel or aluminum. Concern for safety and long-term ability to function should be considered and monitored.
- Metal (steel or aluminum) fuel tanks welded from stamped sheets. Although this technology is very good in limiting fuel emissions, it tends to be less competitive and thus less on the market, although until recent times automotive fuel tanks were almost exclusively made from sheet metal.
Metal is cheaper, but there’s more design freedom with plastic. Plastic tanks are about 30 percent lighter, and they generally don’t have seams, which makes them less likely to rupture in a crash.
Metal materials are beneficial for fuel tanks because of their durability and heat resistance. The ability to withstand high temperatures is essential in building a fuel tank, as it may get scorching while the vehicle runs. You can usually expect to see steel fuel tanks on diesel vehicles and aluminum ones on gasoline-driven vehicles. This is because of their resistance to corrosion and rusting.
Plastics don’t generate sparks, and they’re a bit more flexible than metal - in the sense of springing back into shape after impact. When a steel tank absorbs impact energy, it crumples and often bursts at the seams. Plastic fuel tanks are very tough.
The capacity of the fuel tanks
The maximum distance a combustion-engine powered car with a full tank can cover is the product of the tank capacity and its fuel efficiency (as in miles per gallon). While larger tanks increase the maximum distance, they also take up more space and (especially when full) add to the total weight, requiring higher fuel consumption for the same performance. Fuel-tank capacity is therefore the result of a trade-off in design considerations. For most compact cars, the capacity is in the range of 45–65 liters (12–17 US gal); the original model Tata Nano is exceptional with its 15-liter (4 US gal) fuel tank. SUVs and trucks tend to have considerably larger fuel tanks.
How thick is a plastic fuel tank?
The plastic fuel tanks are 1.5 mm to 5 mm thick. Steel or iron fuel tanks are similar ranging from 2.5 mm to 5 mm.
A common misconception is that plastic fuel tanks are flimsy because of their lightweight composition. Then you have to consider the fact that different plastic materials vary in strength, impact resistance, and weight. However, if you are still unsure about the durability of a plastic fuel tank, look at its thickness.
Typically speaking, thicker is better when it comes to plastic fuel tanks. As mentioned earlier, plastic polypropylene is the most flexible and lightweight type of plastic. However, this also means that it can be considered weaker than other types of plastics.
How full should you keep your gas tank?
There isn't a perfect answer to this question, so the best advice is always to fill up as you go. It is said not to let your fuel level drop below the quarter tank line because it can be hard on your fuel pump.
In addition to this general rule, you should never keep too much fuel inside your tank for too long. To clarify, keeping gas in your tank for more than a month can cause build-up on the tank wall. Over time this could create cracks that could be detrimental to your car's fuel system.
Some recommend that you always keep at least 1/2 tank no matter how often you drive because it is easier for your car's engine to burn gasoline close to the tank's bottom.
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