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Draining Fuel

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I almost didn't get the Stationary Engine List done this month, thanks to two weeks of horrendous computer problems. When I finally got back on-line and downloaded all the mail there was such a suitable-looking thread that I abandoned my backup restorations and got to work! A contributor from Canada, for whom thoughts of winter come early, began this thread, and the replies reflected, to a certain extent, the geographical variety of contributors.

I was wondering what the general opinion is on draining fuel tanks for the winter on gas engines. 1 have always done it, then started out in the spring with fresh gas, but some people tell me they don't bother. Thoughts?

In my opinion, nothing serious will happen if you let untreated gasoline sit over the winter. I have, however, encountered some difficulty with engines stored for a few years.

I'm not sure about modern gas, but a few years back I had to get a motorcycle going that had been in storage about five years. The shutoff valve leaked fuel into the carbs, where it evaporated. The resultant varnish built up to 3/16-inch thick in some places. I came close to having to throw both carbs into the trash pile.

I've also seen engines where dried varnish completely plugged up the gasoline lines, check valves, etc. Of course, they had been stored for years. Bottom line: Over the winter, don't worry about it. Long-term, drain.

One argument in favor of draining is that next season you may favor other engines in your collection, and this one might not make it out to play. Then it moves farther back in the shed and misses another season. Pretty soon it's five years later and the tank is filled with stinky goo.

We just bought a home in Florida that came with a riding mower that hadn't been run in over two years. The original gas was still in it and the gas can was about 3/4 full and uncapped. I fully expected to have fuel system problems, but it started right up and ran fine. After mowing the yard twice it ran out of gas, so I poured the two-year-old contents of the gas can into it and finished mowing. No problems.

I guess that when I put fresh gas into it, it will decide (a la Murphy's Law) to make life miserable! That's not to say I advocate long-term storage without draining the gas - I seem to have been lucky in this case.

I've never bothered, and so far haven't encountered a problem. Little two-stroke engines in things like weed-eaters and chain-saws have started right up after as much as 10 years of sitting, just by adding fresh fuel. I did find a Briggs & Stratton a bit cranky on the first tank of gas, which had evaporated down to maybe 30 percent of its volume - very sour stuff. I just topped it with fresh gas, primed it with a splash of fresh gas in the carb, and it was fine.

Two-cycle engines, especially ones running rich oil mixes, can be a problem to start after a lay up. The fuel evaporates and leaves the heavier stuff, which is not very volatile, making for hard cranking.

I've never had a problem from not draining fuel tanks over the winter. However, I have encountered a stale smell in the gas if an engine sits for two or more years.

I would be more concerned with the fuel bowls on carburetors of small engines and lawnmowers. You should drain the tank, then run the engine until it is out of fuel.

Over the years, I've dealt with too many springtime hard starters. The gas can I use for outdoor power equipment never gets filled without putting Sta-Bil in it first. That's the same gas can that I use to fill my old engines, and I use gas from it to mix all my two-cycle gas. 1 don't drain anything, I fill the tanks up for the winter.

The last time I needed my generator it had been sitting in my open garage for almost two years. It started first pull. I use Sta-Bil on all my mowers, tillers, chippers and the like, and 1 can go out in the spring and everything starts up like I used it last week.

Sta-Bil works really well as long as you fill your tank full.

I don't drain the fuel tanks, but as autumn approaches I start treating my gas with Sta-Bil. It doesn't cost a lot, and I don't face spring with tanks, carbs, mixer, etc., full of gum. The last time I forgot to use it, it cost me $75 for a totally wrecked chainsaw carburetor, tank and engine. No trouble remembering since.

The following comment is from Australia, where engine show season lasts all year round!

I make sure the petrol engines are empty if they are going to sit for a while, even if it is only going to be for a few weeks. Modern unleaded fuels seem to go 'off' pretty quick, and 1 will not even think of putting LRP (lead replacement petrol) in any of my engines. It goes off quick and fouls spark plugs like crazy. My 12 HP Root & Vandervoort will not even fire unless I put fresh fuel in it, and I know of a few other people with igniter engines who have found the same thing.

I don't see how you guys (and gals) can cope with having to put your toys away for a few months every year! I would go stir crazy if I had to go for more than a week without running an engine and more than a month without going to a good engine display.

If you think you have a problem with fuel gumming up, go buy some racing fuel and put it in your tank - it will clean up any varnish. I used it by mistake once in a crawler that had been sitting for a time. There was no regular gas around, so I grabbed the fuel for the race truck and thought, 'what the heck,' and used it. It ran really rough at first and then started leveling out. Took the carb off just to look and it cleaned up on its own.

On the subject of sour gas, has anyone noticed that two-cycle gas mix does not seem to go bad as fast as straight gasoline? I usually mix up a two gallon batch of 32:1 for the weed-eater about once a year. Never seems to go bad, even at the end when I empty the can. Is it possible that the two-cycle oil acts as a fuel preservative? I have used this mix in the Hercules and am considering going to it on all the engines because of its long-lasting qualities. Seems the top cylinder lubrication of the mix would be useful, too. Any comments?

I've thought the same. I think two-stroke oil helps to keep the gum from solidifying as the gas evaporates. Makes a sort of grease instead. Lots of people can tell you it doesn't always work, of course.

With luck, this article will reach the GEM readership before all your preparations for winter storage are complete. Of course, don't forget to drain your water hopper - freeze cracks are a lot more difficult to repair than cleaning stale fuel from a tank!

Engine enthusiast Helen French lives in Leicester, England. Contact her via e-mail at: Helen @ You can join the Stationary Engine List on the Internet at: