Letter Re: Military Surplus Gasoline Cans–Questions on Cleaning Procedures and Venting

Hi Jim.
I recently bought several used five gallon military gas cans over the Internet. Since they are used, they arrived with some remaining liquid residue in them. I don’t know what it is, other than it is not gasoline. Also, the lids are the kind that close down securely with a latch and don’t appear to be vented like the gas cans bought in a hardware store. I have several questions. (1) Do you have any suggestions for cleaning them out so that I can store gasoline in them? (2) What is the purpose of the cans being unvented? (3) What are the pros and cons of the cans being unvented? (4) Are there any dangers peculiar to unvented gas cans that I need to be aware of? Thanks for a great blog, I have been a regular reader from the beginning. – Joe.

JWR Replies: In answer to your questions:

1) Ironically, the best solvent for cleaning a used gasoline can is… gasoline. When cleaning a 4 or 5 gallon can, in a well-ventilated place, well away from any open flames and taking proper static electricity grounding precautions, simply put one quart of fresh gasoline (the octane number is unimportant) in the can, seal it, and then shake it vigorously for two minutes. Wait five minutes and then give it another two minute shake. Immediately pour out that gas and treat it as you would any other toxic waste. (Do NOT attempt to run it through any sort of engine. At this point it is only suitable for making napalm.) Then repeat the entire process, using another quart of fresh gasoline. Again, discard that gas. At this point the can should be clean enough to use for storing gas for use in engines.

2, 3, and 4) I’ve never heard of an unvented military gas can, but I don’t have much experience with some of the foreign military designs. U.S. mil-spec gas and diesel cans alway have vents. Look closely at the filler neck. It will probably have one or two small vent holes, possibly under the cap’s rubber seal. Unvented cans are a safety hazard in my estimation, because they would be at risk of leaking or rupture with changes in temperature or elevation.