Reading the gas prices thread brought this question to mind. They say that if you keep gas over winter (as in a gas can for lawnmowers, etc.) that you need to add a stabilizer to it, so I'm wondering how long it should keep in a vehicle without worrying about it?

The question came last week from my daughter as we drove into the country. I don't drive much at all, just around town to buy groceries, etc., and I haven't bought gas since March, so she was asking if it would harm the car to not use the gas in that length of time. Am I causing myself problems? 

 

 Good question, Pat. I dont know but my Mom is the same. She didnt drive Jan til recently. Car seems to be Ok. Hope someone knows about this. Babs

 I hope so, too. It may be better to just buy a half tank at a time. 

Pat, my Dh told me it takes about 6 months to a year for gas to go bad. He said you would know because it would start to shellac. I know it has a different odor to it, so you should be able to tell that way too. I left the gas in my lawn tractor over the winter, no stabilizer, and used it last weekend to mow. No problem so far.

Kathy

 Thank you! And thank your husband for me, please. I probably couldn't tell if it turns to shellac, but I might notice the smell. Even I should burn up a tank of gas in six months, though. 

You're welcome Pat.

I did a lot of reading about this when I bought a generator for home backup, and I wanted to keep a 3-day supply of gasoline (out in the shed, not the house!). For storage of more than 30 days, all of the small-engine manufacturers recommend either using a fuel stabilizer with a full tank of fuel or draining the fuel system completely.

The gasoline sold now is not the same stuff as 20 or even 10 years ago. It has more volatiles in it that evaporate and change the characteristics of the fuel, and a fuel stabilizer slows, but does not stop, the evaporation. The maximum time you can keep the fuel is two years with a double dose of the stabilizer. Without stabilizer, all the gasoline companies say use it within 30 days.

Depending on the car you may be heading for problems by not driving the car much, but that is better than not driving it at all. Try to keep the fuel tank full to reduce water condensing inside the tank. I learned about this when I owned an airplane that I flew about once a week, and was told to always fill the tanks when putting the airplane away. What happens is that cooler temperatures overnight cause high-humidity air to be drawn into the empty volume of the tanks, and the moisture in the air will then condense inside the tank.

If the tank is kept full, there is less empty volume for air to move in and out of. Since I gather you just drive your car short distances a few times a week, I'd say keep the tank above 3/4 capacity and you should be all right. I gather you use perhaps a tank of gas a month. If that's the case fill it up once a week or at least once every other week. What you want to avoid is having a near-empty tank for long periods of time.

I once had a pickup truck that had two tanks, I didn't use it much for long periods, and one tank rusted through from the inside from water accumulation due to condensation. It was about a $300 replacement ten years ago. If your lawn mower, tractor, etc. is stored with a full tank you might get away with not using a fuel stabilizer or draining it, (including the carburetor) but I've always drained mine.

If you're going to store it, the owner's manual for your car should have a section on long-term (more than 30 days) storage. If it was me, I'd use a fuel stabilizer and make a point to drive it at least every other week. Don't just let it idle in the driveway for ten minutes, that's worse than not running it at all. The engine and drive system need to get up to full operating temperature for a while to evaporate the water that condenses in the engine and transmission. This means drive it for 20-30 miles at highway speed if possible.

 Thanks for the in depth explanation, Walt. I bought this tank of gas on March 12 and I have three quarters of a tank left. I guess I'd better top it off.  I do drive at least once a week and often two or even three times, I just don't need to go very far from home most of the time. Starting this week, I'll be driving out of town about 10 miles every week, so that should help. 

Don't mean to frighten folks about storing gas but I had an odd situation occur on Sept. 11 2005. I went to do some shopping and put my empty plastic gas can in the trunk of my car. I went to the gas station, filled the car and the gas can and went to BJ's. I was in and out in 30 minutes. I usually put my groceries in the back seat but I open the trunk instead. I discovered that 4 of the 5 gallons I had purchased had leaked into the back of the trunk. I went inside the store and called the fire dept. They showed up with a HAZMAT team and secured the parking lot. The firemen said that had I started the engine or even slammed the trunk shut, it could have set a spark and the car would have exploded. Even talking on a cell phone or tossing a cigarette butt could have caused an explosion. The car had to be disabled and hauled to a dealership. We ended up trading it in for another car because the gas leaked into the back seats. Turns out that a rodent had gnawed on the lower corner of the container. We store our container in a small shed with our lawn equipment. The firemen did say he had seen damage like that done to other plastic containers before. However, when we went to find a metal gas can, they no longer sell them. Lesson here: Always check your plastic gas cans for leaks.

I never haul gas inside a car or trunk if I can help it. I always try to get someone with a pickup to carry it in the back when I need it for the lawn mower. That's the only reason I would store it, but gas doesn't frighten me to that extent. Maybe because I'm an oldster who remembers cleaning up paint with gasoline, and pouring it into vehicles from open containers. I worked in the hayfield when I was young - a totally different scene from the hayfields now. The smell of gas mixed with oil and fresh hay still makes me nostalgic. 

I don't know if metal is better than plastic when it comes to that type of storage because dings and dents can cause leaks, too.