Old Gas

We received the following question regarding old gas; combined responses from both Rob and Dave are given below.

I am a proud owner of a 1975 Super Beetle convertible, which has been sitting for at least five years (it was running when put in storage). What is the best way to flush the old gas and line without pulling the gas tank, if any?

For a car which has been sitting for more than six months, you need to clean both the fuel system and the engine oil system, and get the engine re-oiled before actually starting it. So first drain the oil from the sump and refill it with fresh oil. Then remove the spark plugs and squirt a few cc of engine oil into each spark plug hole. Drain the fuel tank (per one of the procedures below), and on Standard Bugs remove the outlet and clean the in-tank wire gauze filter, or replace it if it's corroded (replacements are usually non-corroding fine plastic gauze filters). Replace any other fuel filters in the system. Fill the tank with fresh fuel, and add some fuel injector/carburetor cleaner at the recommended rate. Now remove the inlet hose from the top of the carburetor and place it in a bottle, and remove the carburetor and wash out the float bowl in fresh fuel then replace it and pre-fill the bowl with fresh fuel. Spin the engine on the starter until fresh fuel is entering the flushing bottle (maybe 10-15 seconds). The fuel pump works off the cam shaft, so it will pulse fuel every second engine revolution – it will take a few seconds of cranking to draw fuel from the tank, then you should see a nice strong squirt-squirt into the bottle. Then replace the spark plugs, connect everything up and fire it up.

This process will do several jobs at once. The fuel injector/carburettor cleaner will help flush any varnish etc. from the sides of the tank and from the fuel lines, fuel pump and carburettor passages and hold it in suspension in the fuel until it is burnt. Removing the fuel filter from the tank (Standard Bugs only) will determine if you might have a future problem with rust flakes in the tank (link to our "rusty tank" article). If the engine has not been run for months, then it will be oil-dry, so removing the spark plugs, priming the cylinders with oil and spinning it on the starter with the spark plugs out will pre-fill the oil passages with fresh oil without any load on the engine, and of course spinning the engine will also flush the fuel lines of any old fuel.

Gasoline tends to get oxidized and deteriorate after 4-6 months of non-use and will be for the most part useless after one year. Since the more volatile components will evapourate first and these are generally the higher octane components the octane number will be severely diminished and the gas may have also become both moisture laden with water vapor, and or particulate matter if it was not in a full and sealed tank when last used. The old fuel might still burn, but it will be inefficient, dirty, low octane, and probably damage your engine.

Any airspace in a gas tank or storage container (plastic or metal), allows for the collection of moisture over time which will also damage gas. The VW tank does not have a sealed venting system, so some air will be able to get into the tank as the fuel evapourates. This small airflow over a long period of time, or during times of high air moisture, can lead to damaging moisture collection most primarily if the tank was less than full.

Also, stored gas can collect particulate matter, rust, dirt, etc., which can clog fuel lines, filters, and can harm both carburetors or fuel injectors. Old gas also creates what is called "gumming" or "varnish" which will cause clogging and sticking within carburetors or fuel injectors regardless of ignitability. If this problem occurs you might be faced with a carburetor rebuild and or injector servicing which can become costly.

If your stored gas is a year or more old it is best to just empty it and take it to a hazardous waste recycling center in your area. This is typically a free service but you may have to make an appointment first. It is best to look it up in your phone book and or consult your local landfill office.

To remove old gas from your car there are a few methods:


Gas Removal Method #1 – Draining –

With Bugs (both Standard and Super) it is easy enough to pull off the rubber hose at the outlet under the tank, which would completely empty it. Be sure to have at hand a container which will hold 10.6 gallons of gas! With standard Bugs, remove the outlet to get at the gauze filter inside the tank to see if you have a problem with rust in the tank.

Gas Removal Method #2 – Siphoning –

Go buy a siphon kit at your local auto store (they are typically less than $15.00).

  • Insert the suction tube end of your siphon/suction tube approximately three feet down into the bottom your gas tank.
  • NOTE: Alternately, on both Standard and Super Bugs, you can remove the fuel sender unit in the top of the tank and insert the siphon there. It would sit right on the bottom of the tank to get all the fuel out.

  • Place the other drain end of tubing into your storage container (such as a gas can or perhaps a clean five gallon paint bucket).
  • Pump the siphon handle and get the fuel flowing out of the tank. You may need to keep pumping to keep the fuel flowing. It is also best to try to have the storage container at a height below the fuel level of the gas tank as this aids in the siphon effect.
  • Once the fuel seems to be completely drained out, move the siphon tube in a few more inches in the tank (6-12 inches), re-pump, and then move the tube a few inches back and re-pump again to make sure you have removed 99% of the gas in your tank.

Gas Removal Method #3 – Tank Removal –

The only other way to remove the gas would be to remove the gas tank completely from the vehicle, which is a bit more difficult. We have a fuel tank removal procedure for the Super Bug (see Fuel Tank Removal); the procedure is similar for the Standard. If you plan to do this, be aware that a full or even half full tank will be quite heavy as one gallon of gas weighs six lbs. Draining the tank would be preferable, by one of the procedures above. Then you would need to remove the tank only if you plan to refurbish it (see Fuel Tank Refurbishment).

PLEASE NOTE – Drilling a hole in the bottom of the tank to remove the fuel is not a good idea for obvious reasons!

NOTE: Once you have drained the tank and completed any refurbishing activities on the tank or the gas (or both), refill the tank completely with fresh HIGH octane fuel, and add some fuel injector cleaner at the highest rate recommended on the bottle (the Standard Bug tank is 40 litres/10.6 US gallons/8.8 Imperial gallons; and the Super Bug tank is 42 litre/11.2 US gallons/9.2 Imperial gallons). Once you have used that tank of higher octane fuel, you can go back to the normal octane for your car - [91RON/87AKI for normal compression 1500/1600s and 87RON/84AKI for the lower compression 1300 and 1200 engines.

NOTE: Finally, take the old gas to your local hazardous waste center!


If your stored gas is aged six-months or less, you can most likely re-use it or recondition it. There are gas additive products available to rejuvenate old gas, and aging/varnish prevention products such as STABIL to add to gas-powered engines.

If the gas in a car’s tank is six-months or less old and is say half full or less, then just fill up the remainder of the tank with fresh high octane gas (before driving the car) and add in some carburetor cleaner additive, OR fuel injector cleaner additive depending on your cars fuel mix/ignition system.

Ideally it is best to re-condition old gas with a ratio of 4 or 5 to 1 new to old. (4-5 parts new gas to 1 part old gas).


If you have siphoned out the old gas first to more properly recondition it, look for water in the gas (water will separately pool in the bottom as water is heavier than gas). Also look for particles of dirt, rust, flakes, etc. that may also have collected. Next, get an old cotton t-shirt or paint sprayer filter and use either style cloth filters to transfer the gas into a clean container. Thus as you pour the gas make sure you are pouring it through the filter. Also, if you see water pooling in the old storage container then STOP your pouring before the water is transferred to your new "clean gas" container!! Then properly dispose of the remaining old gas that contains the water pool or beads.

To recondition your newly filtered old gas add in the purchased additives as mentioned earlier and add in brand new gas in a ratio of 4-1 new to old so as to thin out the old gas with new gas. You can now reuse this gas in your four-stroke engine car, motorcycle, lawnmower, go-cart, ATV, boat, watercraft, etc. or could use it to make two-stroke oil mixed gas.

Please note that it is NOT recommended that you use reconditioned gas in any fuel injected engines but only in carbureted engines. This is due to the octane difference variables of your re-mixed gas and the computerized sensitivity of most all modern fuel injection systems.

To avoid this hassle in the future drain or siphon out gas from any stored vehicle within three months and immediately use the gas in another running vehicle. If you are storing an engine over a season (such as winter for lawnmowers and motorcycles), make sure to drain all the gas from both the tank AND fuel lines AND carburetors OR make sure to add appropriate amounts of a product such as STABIL or STABIL-STORE to a FULL tank before storing it for the season. A full gas tank will also greatly help to keep moisture from building up because it leaves no airspace for water vapor to collect.

It is also highly recommended to start the engine once each month and allow it to run for 10 minutes to get to normal operating temperature as this helps prevent other problems such as oil sludge build-up and cracking of things like gaskets and hoses and generally circulates all fluids.

If you cannot get a stored engine running after having used fresh gas or reconditioned gas, first check your battery for sufficient charge, and it would also be a good idea to change the fuel filter if the car engine has over 100,000 miles. A fuel filter typically costs less than $20 and is fairly easy to replace (see our fuel filter procedure). There are obviously many other potential problems that will prevent your engine from starting. In any case, if you cannot start your engine there only two basic reasons: FUEL or SPARK.

Remember, any engine, just like your own body, needs routine clean fluids and routine exercise. Avoidance of this preventative maintenance principle can and will lead to much greater troubles and will always cost you more in the long run! Always stay ahead of the curve!

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