Technical question, re: chemistry/petrol

House of Usher · 15 June, 2006, 08:03:38 PM

I was reading the letters page of Robert Kirkman's "The Walking Dead", and there were a couple of letters that highlighted the importance of knowledge/research when writing plausible fiction.

One pointed out that early issues showed it snowing, despite the story being set in and around Atlanta, Georgia. It's generally too hot there to ever snow. Kirkham owned up to the mistake, and put the anomalous weather down to 'erm - climate change'.

Another letter writer raised a very interesting point relating to the condition of petrol in the post-apocalyptic world. The survivors have been managing by siphoning petrol from the tanks of abandoned cars; but the letter writer points out that they won't be able to do that forever, because petrol oxidizes over time. I looked it up via google, and apparently petrol has a shelf-life of up to 12 months, and diesel 18 months to 2 years.

Does anyone have any expertise in this area, that they could shed light on the matter? What makes petrol go off, how long can it be stored successfully, and what can you do (industrially, now; not after the apocalypse) to preserve petrol for longer?

Matt Timson · 15 June, 2006, 08:18:40 PM

Planning for the apocalypse, Ush?

WoD · 15 June, 2006, 08:21:08 PM

Keep it in your bath tub, and stir it daily with a stick except for the first thursday of every month, when you must use rhubarb.

WoD · 15 June, 2006, 08:21:42 PM

You can tell you lot did GCSE's and not o-levels...kids today, what do they bloody know!!!

House of Usher · 15 June, 2006, 08:21:46 PM

No! I've no intention to survive such an event at all! I might try to keep going as long as I can, but with the proviso that I'd be expecting to succumb to the inevitable before very long.

Dudley · 15 June, 2006, 08:26:23 PM

What makes petrol go off
- Oxidization

how long can it be stored successfully
- Infinitely, in a 100% de-oxygenated environment

what can you do (industrially, now; not after the apocalypse) to preserve petrol for longer?
- Don't let any air get to it.

House of Usher · 15 June, 2006, 08:28:42 PM

Does that keep it safe from anaerobic bacteria too?

Slippery PD · 15 June, 2006, 08:33:33 PM

James is completely correct. Sealed in a unit ie a petrol tank, it would probably last more than 18 months. Oxygen is pretty much minimum there so shouldt oxidise too quickly. Obviously the more petrol is removed the more Oxygen is available....

I could be really sad and write the equation but its been 10 years sincd I used my degree for anything other than answering trivia questions like this....

Slips BSc (Hons) Applied Chemistry

House of Usher · 15 June, 2006, 08:38:09 PM

I just found this in Wikipedia:

"When gasoline is left for a certain period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel." This will cause gums to build up in the cylinders and also the fuel lines, making it harder to start the engine. Gums and varnishes should be removed by a professional to extend engine life. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1-2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting."

I can see what it says, but I'm interested to know about general rules and exceptions.

WoD · 15 June, 2006, 08:44:18 PM

did you know that if your petrol tank is leaking you can use soap (the hard kind not liquid) to seal (a small) hole, and it will set as it reacts with the petrol.

Also, egg white in a radiator can be used to fix a small leak in the cooling system, as the egg cooks as it is pushed out through the gap.

scutfink · 15 June, 2006, 09:06:24 PM

Also you can make a bomb out of a chocolate bar and a sachet of salad creme, eh McGuyver?

scutfink · 15 June, 2006, 09:49:21 PM

Also IIRC, there's supposedly some kind of pocket you can keep petrol in, between Geological strata, where it keeps for millions of years, allegedly...

Art · 15 June, 2006, 09:50:14 PM