Can you mix old gasoline with new gasoline?

Answer 1

OLD GAS AND GAS RECONDITIONINGYes and no. Gasoline tends to lose oxidation and deteriorate after 4-6 months of non-use and will be for the most part useless after 1 year. While it certainly will still ignite and burn, the octane content for any engines usability is severely diminished as well the gas at this point 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.

Any airspace in a gas tank or storage container (plastic or metal), allows for the collection of mosture over time which will also damage gas. Even sealed tanks such as your car have a pressure relief valve than allows some airflow in the tank thus allowing a vacuum to not occur in the tank. This small airflow over a long period of time, or during times of high air mositure, 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 carb 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 THAT IS OLD BY 6 MONTHS OR GREATER:

GAS REMOVAL METHOD #1 (SIPHON) -- A : Go buy a siphon kit at your local auto store (they are typically less than $15.00) You will also need a big and long flathead screwdriver ~10-12". STEP 1: Remove your gas cap and first make sure to touch the screwdriver on some metal place on the car body first to de-static the screwdriver. (we don't want any explosions here! ) STEP 2: Slowly place the long screwdriver down into the gas hole to open the metal baffle / valve that is typically near the opening of the hole. STEP 3: Insert the suction tube end of your siphon / suction tube approximately 3 feet down into the bottom your gas tank. STEP 4: Place the other drain end of tubing into your storage container (such as a gas can or perhaps a clean 5 gallon paint bucket). STEP 5 : 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 and have the storage container at a height below the fuel level of the gas tank as this aids in the siphon effect. STEP 6: Once the fuel seems to be drained out move your siphon tube in a few more inches in the tank (6-12"), re-pump, and then move the tube a few inches back and repump again to make sure you have removed 99% of the gas in your tank.

GAS REMOVAL METHOD #2 -- (TANK REMOVAL) : The only other way to remove the gas would be to remove the gas tank completely from the vehicle which would require more skill, tools, jackstands, and a service manual. If you were to do this also be aware that a full or even half full tank will be quite heavy as one gallon of gas weighs 6lbs. Thus you may want to at least siphon out what you can first before removal. Just make sure not to pin yourself under the car with the gas tank! Also...drilling a hole in the bottom of the tank is not a good idea for obvious reasons!

Next, take the old gas to your local hazardous waste center!

GAS THAT IS OLD BY 6 MONTHs OR LESS:

If your stored gas is aged 6 months or less then you can most likely re-use it or recondition it. There are gas additive products available to re-oxygenate old gas and aging / varnish prevention products such as STABIL to add to gas powered engines that you do not use often such as periodic use 4-stroke style lawnmowers and motorcycles.

If the gas in a cars tank is 6 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 first before driving and also add in some carb cleaner additive, OR fuel injector cleaner additive depending on your cars fuel mix / ignition system.

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

CLEANING / FILTERING / RECONDITIONING

If you have siphoned out the old gas first to more properly recondition it look for water in the gas which 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 (from a hardware store or Home Depot perhaps) 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 4 stroke engine car, motorcycle, lawnmower, go-cart, atv, boat, watercraft, etc. or could use it to make 2-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 3 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) then make sure to drain all the gas from both the tank AND fuel lines AND carbs 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. ( or 15k on a motorcycle) A fuel filter typically costs less than $20 for any car and is fairly easy to replace. There are obviously 1,000 other potential problems I cannot get into here so you may need a professional mechanics advice. In any case if any engine is NOT able to start this is only due to 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!