Winterize Your Classic the Smart Way

For enthusiasts across most of the country, winter is when muscle cars and hot rods retreat to the garage. The seasonal pause is a chance to protect your investment, but it also invites a persistent myth: that starting your engine and letting it idle every few weeks is good for it. The habit feels caring, yet experts say it can do more harm than good.

Lake Speed Jr., a certified tribologist—a specialist in lubrication science—explains why. When you start a parked engine and let it idle briefly, coolant temperature may rise to around 180°F (82°C), but engine oil lags behind. Oil warms more slowly and often fails to reach the critical 212°F (100°C) threshold during a short idle. Even after eight to ten minutes, the oil can still be below that point.

That number matters. Combustion naturally produces water vapor, and some of it condenses inside the engine as the engine cools. Water doesn’t blend with oil, but in a partially warmed engine it can linger within the crankcase. There it meets other combustion byproducts—acids—and together they create a corrosive cocktail. Left to sit for months, that mix can attack soft bearing materials and encourage internal rust. If your classic uses a carburetor, the risk compounds. Choke-enriched mixtures during warm-up can allow raw fuel to slip past the rings and into the oil. Gasoline is a solvent; it thins oil, undermines its protective film, and amplifies wear.

The fix is simpler than old habits make it seem. Before you put the car away, change the oil and filter. Fresh oil begins the storage period with the fewest contaminants and the strongest additives. Then bring the engine fully up to operating temperature—specifically, drive the car long enough under load for the oil to surpass 212°F. A short idle in the driveway won’t do it. A proper drive ensures that moisture boils off and volatile fuel dilution evaporates. Once you’ve done that, park the car and let it sleep. Resist the urge to “just start it.” Unless you can take it out and drive it long enough to thoroughly heat the oil again, that quick warm-up only reintroduces condensation and dilution.

While you’re preparing the car, don’t overlook the other fluid that quietly safeguards your engine: coolant. Over time, coolant degrades, its corrosion inhibitors weaken, and it can become acidic. That acidity can encourage galvanic corrosion in the radiator and throughout the engine. There’s an easy way to check its condition with a basic multimeter.

Set your multimeter to measure millivolts (mV). Attach the ground probe to a clean, unpainted metal part of the radiator or engine. Carefully dip the positive probe into the coolant in the radiator neck or overflow without letting the probe touch metal. You’re measuring the electrochemical potential in the coolant; the reading offers a window into its corrosive state. Low readings—like 20 millivolts—signal healthy coolant. As the number rises, so does the risk. Up to roughly 250 to 300 millivolts is generally acceptable, but readings above 400 millivolts indicate the coolant has grown acidic and should be replaced. If your test shows high acidity, flush the system and refill with the proper mix and type for your engine, using distilled water when required by the coolant manufacturer. This simple check can prevent costly damage to radiators, heater cores, and water pumps.

Consider how these steps work together. Fresh oil removes the acids and fuel contamination that can stew all winter. Achieving full oil temperature drives off moisture and stabilizes viscosity and film strength. Avoiding repeated short starts prevents a recurring cycle of condensation. Monitoring coolant acidity helps your engine resist electrochemical damage during long periods of inactivity. None of these actions require exotic tools—just discipline and a few intentional choices.

If you’re tempted to “exercise” the engine in place, remember the difference between coolant temperature and oil temperature, and between idling and operating under load. The dashboard gauge may reassure you, but only a real drive thoroughly warms the oil. When winter storms and salted roads make that impossible, your best move is to let the car rest—properly prepared, sealed against the elements, and waiting for spring.

In the end, winterizing isn’t about doing more; it’s about doing the few right things at the right time. Change the oil and filter. Heat the oil properly once before storage. Check the coolant’s health and refresh it if needed. Park the car and let it be. Come thaw, your classic will be ready to fire up cleanly, lubricate effectively, and get back to doing what it does best: making every mile feel like a reward.

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