Yea, for sure gas and CO2 emissions are higher when idling, but every start creates more emissions of other molecules, like unburnt fuel, CO, NOx, etc. Of course those are minimal if a short stop and CAT stays hot, but go up as it cools down. Newer cars have the CAT even closer to the engine block, so they heat up faster and cool down slower.CanadianLurker wrote: ↑ What you're saying is generally correct, I'm not sure that the numbers are. I've always seen most analysis just on fuel savings alone and it always comes out that there are 10-15% fuel savings on vehicles equipped with automatic start/stop systems. From there it stands to reason that reduced fuel consumption comes with the added benefit of lower emissions.
But your comments got me thinking and looking around a bit and I found this study:
This study looked at the problem and concluded otherwise. It was initiated to consider the cost/benefit of idling in a drive-thru lane vs shutting off and returning for a re-start shortly afterwards. Here are some points on re-starts with a caveat
• Emissions from restarting were larger, but at least an order of magnitude lower than those from starting a cold engine.
• The catalyst cooled down slowly, so that restarts after times equivalent to a short transaction at a bank or restaurant are unlikely to allow the temperature to drop below light-off and incur large cold-start emissions.
Research Limitations
Data presented here are based on one vehicle at one temperature, with a small number of runs. Therefore, although several conclusions are suggested by this work, generalizations are unwarranted without additional work to confirm the extent to which the results apply
Conclusions
• Idling for more than 10 seconds uses more fuel (Figure 3) and emits more CO2 than engine restarting.
• Idling fuel usage varies from 0.2 to 0.5 gal/h for passenger vehicles across a range of sizes, and increased with idling speed.
• The vehicle warms up faster when driving than it does when idling.
• NOx and THC emissions from restarting are larger, but at least an order of magnitude lower than those from starting a cold engine (Table 2).
• For short stops, it makes sense to turn the vehicle off in order to minimize fuel use and CO2 emissions. At least for the conditions evaluated in this work, the penalty in terms of criteria pollutant emissions is very small compared to 1cold-start emissions.
https://afdc.energy.gov/files/u/publica ... reener.pdf
Yea, I can't remember the last time I've heard of car post 2000 with a failed starter, let alone a post 2010 car. It used to be a problem that you'd be almost guaranteed to have the start fail under 200k KM. My 20 year old BMW with 240k KM is still on original starter.CanadianLurker wrote: ↑ Yes, doing 15 minutes on highway before/after shift will help to replenish the battery but since you already have the equipment it won't hurt to keep an eye on battery health and use the maintainer as needed.
And the worry about the extra starter use is understandable, but isn't something I'd worry about on a modern vehicle like yours. Things are better designed & built compared to the 80's/90's when having starter issues was a more common problem. There are plenty of cabbies out there without automatic stop/start systems who are manually turning off to avoid idling dozens of times per shift x 2 or 3 shifts per day on the vehicle. And not just to reduce costs and save gas but they're operating in areas where it is required under by-laws to avoid idling.
If the women don't find you handsome, they should at least find you handy.