Eric Lai answers readers’ auto questions every week for Wheels.
Q: I’m 8 years old. Why are cars and buses so smoky in wintertime? It smells so bad it makes me sick breathing it.
A: Peter Gerson of GB Auto Service in Thornhill replies:
Actually, what you’re seeing coming from vehicle tailpipes is mostly water vapour (steam). This would normally be invisible in warmer temperatures but can be seen in the cold. You can tell that it’s water vapour because it will disappear fairly quickly, whereas smoke would remain white, blue or black as it drifts away.
Water vapour is a by-product of combustion. That is, it’s produced when the fuel (gasoline, propane, natural gas) is burned, so that’s why it comes out the tailpipe.
More from Eric Lai:
In cold weather, vehicles are programmed to run rich (more gasoline) on start-up to prevent stalling. Immediately after a cold start, the engine is running under “basic operating conditions.” That means it is burning more gas as all the sensors and fancy electronic controls have not yet come online to allow the onboard computer to run the engine at maximum efficiency given the conditions.
The exhaust may smell strongly during the warm-up period, which will vary with temperature, because the engine is running rich and there may be unburned gasoline vapours in the exhaust.
Once the onboard computer becomes active, it should adjust the fuel mixture to prevent this. In any case, after the catalytic converter heats up sufficiently, it will eliminate any unburned gasoline fumes from the exhaust.
Eric Lai adds:
With diesel vehicles, like school buses, the black smoke coming from the tailpipe is indeed smoke and I agree it smells terrible. It seems to linger more in the cold, damp air.
Q: How can I check my speedometer’s accuracy?
A: The easiest way is to find a radar-equipped sign board, if used in your municipality. They’re typically located in school/residential zones, or check local online forums. These units display your speed as you approach the sign, which you can then compare to your car’s speedometer reading.
Columns Everything you need to know about purchasing, maintaining and driving your car.
Become a member
Register now to access all features including:
- Save and ask friends to review vehicles
- Exclusive rebates & offers from local dealers
- Premium content, reviews and tools
- You can unsubscribe at any time. Please Contact Us for details.
All for free!
Already a member?
Registration 2 of 2
Welcome to Wheels!
As a final step we've sent a confirmation to your email address as a security measure. Please click the link in the email to complete your registration.
Terms of services
DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITY
TO THE FULLEST EXTENT PERMITTED BY LAW, TORONTO STAR IS PROVIDING THE TORONTO STAR WEBSITES ON AN "AS IS" AND "AS AVAILABLE" BASIS AND MAKES NO WARRANTIES OR REPRESENTATIONS, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, IN ANY CONNECTION WITH THE TORONTO STAR WEBSITES, THEIR CONTENTS, OR ANY WEB SITE OR CONTENTS WITH WHICH IT IS LINKED. TORONTO STAR DOES NOT WARRANT THAT THE FUNCTION OF THE TORONTO STAR WEBSITES OR THEIR CONTENTS WILL BE UNINTERRUPTED OR ERROR FREE, THAT DEFECTS WILL BE CORRECTED, OR THAT THE TORONTO STAR WEBSITES OR THE SERVERS THAT MAKE IT AVAILABLE ARE FREE OF VIRUSES OR OTHER HARMFUL COMPONENTS.
TO THE FULLEST EXTENT PERMITTED BY LAW, UNDER NO CIRCUMSTANCES, INCLUDING, BUT NOT LIMITED TO, NEGLIGENCE, SHALL TORONTO STAR BE LIABLE FOR ANY LOSS OF USE, LOSS OF DATA, LOSS OF INCOME OR PROFIT, LOSS OF OR DAMAGE TO PROPERTY, OR FOR ANY DAMAGES OF ANY KIND OR CHARACTER (INCLUDING WITHOUT LIMITATION ANY COMPENSATORY, INCIDENTAL, DIRECT, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES), EVEN IF TORONTO STAR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES OR LOSSES, ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE TORONTO STAR WEBSITES, THEIR CONTENTS, OR ANY WEBSITE OR CONTENTS WITH WHICH IT IS LINKED. IN NO EVENT SHALL TORONTO STAR'S TOTAL LIABILITY FOR ALL DAMAGES, LOSSES, AND CAUSES OF ACTION, WHETHER IN CONTRACT, TORT (INCLUDING, BUT NOT LIMITED TO, NEGLIGENCE), OR OTHERWISE, EXCEED THE AMOUNT PAID BY YOU FOR ACCESSING THIS SITE.X