940 Storing a 940 T, Old Gas, and Boosting on Old Gas

I store my 940T over the winter to avoid the salt rot.

I only use 91 Octane (North America), Ethanol Free from Shell.

How long will ethanol-free fuel last before going 'bad'? With the 940 having a plastic tank, is it really necessary to store the car with the tank full?

I heard that boosting on old gas is not a good idea, so I drive the car really easily and try not to boost on the gas that was stored over the winter. Is this necessary, or is 5 month old gas not going to cause any problems?

When storing the car, here are a couple other things I do, some are probably unnecessary;

-Remove the battery so I can keep it inside. This also prevents current running through car wiring which attracts chewing rodents.

-Spray the battery tray and in front of the air box with water and peppermint oil to repel rodents.

-Plug the tailpipe with steel wool to prevent anybody from crawling inside.

-Remove the plastic Volvo floor mats and windshield wipers and put them in the trunk to minimize unnecessary UV exposure.

-Spray the carpets and trunk with a bit of that peppermint spray to discourage anybody from finding their way inside.

Not sure if it's 'bad' but my 740t currently has gas that's about 5 months old but it drives fine, no weird idle or anything.

I would store it with a full tank so no moisture gets in there.

ZVOLV said:

I would store it with a full tank so no moisture gets in there.

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As would I. And I wouldn't sweat it in the Spring.

How good is the Evap system in your 940? If it works properly and seals as designed then you do not have to worry about the fuel system breathing moist outside air into the tank as ambient air temperature goes from cold - warm - cold - warm .... If your Evap system is not so sealed, then filling to the brim before storage reduces the opportunity for air change and the accumulation of moisture in the fuel system. There is no long term net $ cost to topping up before storage so easy to do and reduces any potential issues.

Aside from accumulation of moisture, the other contributor to deterioration of gasoline is exposure to oxygen. Topping up your tank reduces the exposure of the gasoline to oxygen. Gasoline deteriorates in storage. Faster when exposed to air even with stabilizers added. After 6 months of storage, the engine will probably start and should probably run without significant issue. But, there may be some octane deterioration.

As an observation, since you are storing the car outside I would be more inclined to seal off the air intake and the exhaust pipe with plastic. In the winter you can go through temperature swings that can cause the air temperature to drop below the dew point as it enters the cold intake and exhaust system resulting in moisture accumulation inside the the engine and surface rusting.