Directly from the horse's mouth

[Walter R.]

I have been intrigued by conflicting information in this NG regarding the degradation of gasoline over time.

This is what Chevron has to say on the subject and this makes good sense.

1. How long can I store gasoline without it going bad?

Gasoline stored in a tightly closed container in a cool place will stay good for at least one year. It is better if the container or fuel tank is almost (95 percent) full. If the container or fuel tank will be in the direct sun or will be heated above 30°C (80°F) much of the time, add an aftermarket fuel stabilizer to the gasoline when you first buy it. Gasoline-oil blends for two-stroke cycle engines stored under the proper conditions will keep as well as gasoline itself.

[Toller]

Do you think we care what actual authorities say!

[RMD]

Walter,

Someone like Chevron has to give conservative advice, since they don't want anyone claiming engine damage etc as a result of the advice.

The only petrol I've had go so bad that the engine wouldn't start is two-stroke stored in small fuel tanks in things like chain-saws and outboard motors.

It has taken probably >3 years of non-use for this two stroke fuel to go this bad.

Stored in larger tanks and larger quantities and just normal fuel (not two-stroke mix) I've never had fuel go bad so the engine wouldn't start, and I've left some cars for years with the same fuel in the tank/carby bowl. One tow car I own hasn't actually been refueled since

2002 and it still started just fine the last time I started it about a month ago.

Obviously if you follow the Chevron redcommendations, which btw are similar to the instructions you will find in an outboard motor manual, then you don't have any fuel trouble.

If you don't follow the recomendations then you empty out the bad fuel, add good fuel, and the thing usually then starts promptly.

I've started old lawnmowers I own (mower kept as a spare) many years after the last use, and all the old fuel had actually evaporated away, and with fresh fuel and maybe blow out the carby bowl with compressed air they are soon running again as good as new.

Ross

(To get email address ROT 13) ebff [e-mail]

[James "Cubby" Culbertson]

Whatever about Chevron's advice, I had a Harley that sat for about 1.5 years while I went overseas. I came back and it wouldn't start to save my life. Drained the fuel, added fresh and it started right up. I'm a believer that without stabilizer, fuel does go bad quicker than 3 years. Cheers, cc

[Toller]

Exactly! You would expect them to say that gas goes bad in a few months so that no one sues them claiming they followed their advice and 1 year old gas ruined their car.

Think about it; you have backwards.

The question just above it on the Chevron website, about premium gas, is interesting. I have a friend who kept careful records for several years and is convinced that premium gives him 10% better mileage than regular. Just goes to show that anecdotal evidence is inaccurate, cause all authorities say he is wrong.

[Edwin Pawlowski]

What engine? What circumstances? I've never found any difference in my car, but that does not mean a certain engine may not do better.

[Steve Kraus]

It's entirely possible. If you have a car that requires premium and the computer is adjusting (retarding the spark or whatever it does) to avoid knock on lower grade gas it could impact mileage. This will be affected by how the car is driven and how much its being put in situations where these compensations are being made. Years ago I had an old hand-me-down Pontiac that should have been getting premium but I used regular and it would knock on heavy acceleration.

[nicksanspam]

A tank that is not perfectly sealed will exhale gas as it warms and inhale air as it cools, along with water vapor which condenses. Keeping it full reduces the volume of air exchanged when this happens, and shading it reduces the amplitude and frequency of temperature changes.

Nick

[m Ransley]

Check a few motor manufacturer sites Sthil recommends not using gas more than 30 days old. Who cares what Chevron says, they sell it but we have use it and know it lifespan. Plastic containers do allow minute amounts of gasolenes components to leach out. You can smell bad gas, it does not take it that long to go stale. Chevron wont pay for that clogged up carb, you will.

[Toller]

Of course you are right about that! His car was designed for regular, and ran fine on it. He simply "got" better mileage on premium. Sorry for not stating that relevant detail.