Should you fill up your classic before parking for the winter? | Fuel Facts

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Winter’s fast approaching, meaning many classics will head into hibernation soon. Should you be worried about the impact of longterm storage? We asked Zachary J. Santner, senior specialist of quality at Sunoco, for some winter storage advice. 

His first tip? Fill up the tank before any prolonged parking: “A full tank won’t have as much headspace and won’t breathe as much,” he says. That full fuel load will prevent moisture from condensing in the tank–moisture that can lead to stale fuel and corrosion. Whenever Santner has encountered a rusty gas tank, he says, the damage is usually found at the headspace. 

 “If you can,” he notes, “fill it up with non-ethanol.” Non-ethanol fuel is less likely to absorb moisture from the atmosphere than the ethanol-enriched fuel commonly found at the corner station.

If you can’t find non-ethanol fuel, he continues, then fill up with premium. The higher-octane fuel is simply more stable, he explains, and won’t go stale as quickly as regular-grade fuel.

Sunoco’s Optima combines both of those properties into one fuel designed for long-term storage, he says. It’s a high-octane, oxygen-free fuel that’s packed with antioxidants and corrosion inhibitors.

If you don’t have a fuel designed for storage handy, Santner suggests combining pump gas with a fuel additive–ideally one with an anti-oxidant package containing sterically hindered phenols. That info likely won’t show up on the safety data sheet, but he advises that the popular red additive does work well. 

To properly mix the additive with the gas, first pour the additive into the tank. Then fill up the rest of the tank with gas.

Where the car sits also matters, says Santner. Storing the car in a garage will help keep moisture at bay. A climate-controlled garage is best, but any garage is better than outside. 

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7aull New Reader
9/29/22 12:26 p.m.

14 years on interior Alaska (outdoors, under a cover) storage of my 1980 RX7:

full tank as described, with a can of SeaFoam thrown in first.

THEN- shut off the fuel pump (mine, electric: I wired in a switch to do this. Yours may have a fuse you can pull...) and run the car till it stalls. Idea is to get as much sitting gas out of the carb as possible. Don't know if this is a good idea for injected cars...

THEN: pop the air-cleaner assy, lay a piece of plastic bag over the mouth of the carb to seal off the system (moisture barrier) from that end. Re-seat the air cleaner.

Started up 1st twist of the key every spring after a 7 mo sleep!

Stu A

80GS RX7


Tim Suddard
Tim Suddard Publisher
9/29/22 1:22 p.m.

In reply to 7aull :

Great advice!

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