Question 1

When should I switch to winter tires?

Accepted Answer

Once average daily temperatures drop below about 45degF (7degC), because all-season and summer tire rubber stiffens and loses grip below that point regardless of tread depth. In practice that means switching in October or November across most of the northern US and Canada, before the first snow rather than after it.

Question 2

Does cold weather kill car batteries?

Accepted Answer

Cold does not kill a healthy battery outright, but it exposes a weak one. Cold thickens engine oil (harder to crank) while cutting a lead-acid battery output at the same time - roughly half its cranking power near 0degF versus 80degF. A battery that starts the car fine in summer can fail on the first cold morning, so testing it before winter catches the failure at home instead of in a parking lot.

Question 3

Do I need winter washer fluid?

Accepted Answer

Yes. Summer washer fluid is mostly water and freezes in the reservoir and lines, which can crack the reservoir or pump. Winter-rated fluid is treated to stay liquid well below freezing (many are rated to -20degF/-30degC or lower) and cuts through road salt film that plain water will not.

Question 4

Should coolant be checked before winter?

Accepted Answer

Yes. Coolant does two jobs - it prevents overheating in summer and prevents the block from freezing in winter - and its freeze protection weakens as the mix degrades or gets diluted with plain water. Check the level and, if it has not been changed on the schedule interval, have the concentration tested before temperatures drop, since a coolant freeze can crack the block.

Fall and Winter Car Maintenance Checklist