Stale Fuel
 

Looking for advice. I last filled my Porsche up in September last year, in around November I put the car undercover for winter. With the current lockdown expected to last until around March, the fuel will be 6 months old. I cannot drive the car legally on the road now as the tax and MOT have expired. I've heard stories about stale Fuel, but is it all urban myth? Should I be concerned about engine/fuel system damage? Should I drain the tank and put fresh fuel in? I should note it was premium with a RON of 98, whether that makes a difference.

I don't think you will have an issue, I would recommend putting fuel stabilizer in it. My Yamaha R1 sits for 6 months every year and I put fuel stabilizer in it, but I never have an issue other than the old fuel gets terrible mileage. I tend to leave the tank somewhat empty and then fill it full with fresh fuel before start-up. If you are too concerned, you could turn the car on and let it idle until you burn the fuel off and the tank goes empty. I heard 6 months is not enough time for old fuel to cause engine damage.

Fuel goes stale because of the lighter fractions evaporating off and oxidation.

Power equipment should be drained and run dry, and the fuel in any cans used up at the end of the season.

With their emission controls, car fuel tanks are much better sealed. So less evaporation, and less air getting in to cause oxidation. Volts would go a year of no fuel being added before deciding it was time to burn the old stuff off.

I wouldn't worry about the fuel. You can add a stabilizer(diesel can be used as such). If the tank isn't full, I'd skip on that, and just add fresh gas before starting it up; at least 3 gallons. Some fuel system cleaner wouldn't hurt.

I'd be more worried about the battery dying, and brake calipers freezing up.

Thanks for the advice. The tank is 90% full, I was told to fill it as much as possible to avoid condensation and water mixing in the tank. The battery is brand new, swapped under warranty, however it did die once about 3-4 weeks after sitting so I've rigged up my trickle charger now that keeps the battery level topped up. It's a real pain trying to pop the bonnet with a dead battery in a Porsche as they use electronic switch gear...I have some redex fuel system cleaner, so I'll probably add that to the tank in the spring as a precaution.

I don't think you'll have an issue. I have a pickup truck that only goes a few hundred miles a year. Sometimes it goes over a year between fillups. I never have an issue. I just keep a solar trickle charger plugged into the accessory socket to keep the battery from dying.

I know it is not quite the same, but I buy a gallon of petrol for my Briggs & Stratton mower in the spring, and that lies in the can until the following spring, just taking a pint or so out, as I need it.

Stale Fuel sounds like an outdated urban myth then, perhaps it was an issue with older more fuel sensitive cars. I'll worry not.

It's more of an issue with carburetors and less tightly sealed fuel systems.

The fuel will be OK but letting the fuel stay in very long term can ruin electric fuel pumps. I just had the fuel pump replaced in my mom's '99 Grand Marquis a few weeks ago at only 61K miles. Her car does lots of sitting and 90% of the time a tank of fuel in it will last 3+ months. Over the years I've had cars that I wasn't using and let fuel sit in them for a few years. When I'd go to use them again the fuel pump would be bad. I'm not sure but I suspect part of the problem is the ethanol in the fuel is corrosive toward the fuel pump and I know gasoline will turn into a sticky varnish over a long period of time. There have been many times I've had to clean the carburetor on my mowers after sitting with untreated fuel in them over the winter. I agree you should put in some stabilizer and run the engine long enough to get the stabilizer throughout the fuel system.

I started the car up yesterday, started just fine and ran ok, if a little smokey at first, hopefully just condensation. I cut the video just as the smoke begins.

https://youtu.be/Rj9SloJS4fM