Piston Slap: Parked in the Polar Vortex?

V writes:Here are two questions from a regular, and grateful, Piston Slap reader:

1. How long is best to idle a gasoline engine after starting & before driving off: [A] a few minutes? one minute? [C] until the revs settle down? no need, just drive right off? Assume ambient temperature well above freezing; a shifting style on the sedate side; and a car made in the past 15 years so engine has EFI and EGR and all that. Current ride’s engine is naturally-aspirated and direct-injected, but I sure would appreciate knowing the proper protocol for other combinations too, if different. Several sources over the past years have all agreed on for modern engines, but then just a few months back a Car & Driver column said [A], so now I’m unsure again.
2. Leaving a car (stick shift *of course*) parked: best in gear, best in neutral, or doesn’t matter? Assume the parking space is either not sloped at all, or is sloped and I know enough to turn a front wheel into the curb toward the down slope.

Sajeev Answers:Thank you for contributing and reading! To your first question: not much changed since our last discussion. But were the words “ Polar Vortex” as commonplace in our lexicon back then? Probably, but work with me here! Let’s include engine warm up in the polar vortex: peep this Oil Viscosity Chart to ensure your oil didn’t turn into molasses overnight. If so, let the motor warm up for many, many minutes to let the oil thin out (provided you aren’t using an engine block heater!). More to the point, while restoring my 1989 Lincoln Continental (the aforementioned Pilot Fish), I thumbed through the shop manual’s chapter on Ford’s Insta-clear windshield: while not a popular success, it personifies the engineering effort working to reduce stress in awful weather for both car and driver.Because there’s more to the story than the engine: your glass is iced up, you need to clear snow from the roof/perimeter, your wiper blades/tires are petrified, etc. Long story short: Option D is still the best for the (not carbureted!) engine, but if you’re in the depth of a polar vortex, consider warming up time for the rest of the vehicle. And perhaps your sanity, too. Second question?Park in first gear, add the parking brake and turn aforementioned the wheels if it’s really hilly. Since Houston is flat and totally geographically boring, I just park in 1st. On seriously steep ramps (i.e. flood protection down here), engaging the parking brake before going into 1st isn’t a bad idea. That makes the drivetrain a secondary brake, which isn’t a big concern with a clutch (easily released before starting) but it’s a great idea on an automatic transmission’s inflexible on-off lock mechanism. Have you ever heard a terrible noise when dropping an automatic out of park on a steep hill?

Back to manuals, do only park it in first gear: numerically higher gears require more wheel rotations to move the rest of the drivetrain. What’s great for jackrabbit starts is also great for holding the vehicle on not-perfectly flat ground…Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.[Image: © Timothy Cain/TTAC]