Metal is of course more durable. Plastic can tend to crack and get brittle, especially in extremely hot or extremely cold environments. Metal are more secure; the best locking caps are made of metal, or metal and other materials. The plastic caps (or the coated/covered ones) reduce the potential for sparks. Often there are other requirements which can dictate what type of cap you should use.
Source: www.prweb.com
Locking or Non locking Possibility
As with anything, you do have the choice of caps. Besides colors and the material they are made from there is another important issue. Is it lockable? That might not be a concern.
Some caps require a key to manually unlock it before you can remove the cap, while many have no such protections.
Source: www.raneystruckparts.com
For anyone who spends large amounts of time driving the open road, it is highly recommended that you have a locking system for your cap and even anti siphon devices as well. The last thing you want to have happen is to wake up ready for a long drive only to discover your fuel is gone.
