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rovyko

>lots the transmission at 65000 miles

That's insane... What's better for wear on the engine, turning it off then on or idling in neutral?

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Well for the engine, of course idling

If that's true for newer cars then how come they turn off the engine at the stop lights to save fuel?

Because it saves fuel/emissions?

Corporate average fuel economy regulations [1] set targets for the average fuel efficiency of all the vehicles a manufacturer sells. Since SUVs are popular and higher margin, car companies often have to do tricks like the auto-off engines to offset poor fuel economies in more profitable segments. Manufacturers that want to go over the limits have to pay a penalty or buy credits from their competitors who go under the limit.

Cars with auto-off also have newer technology made specifically to handle the extra stress like self-lubricating bearings and starters rated for >500k starts.

[1] https://en.wikipedia.org/wiki/Corporate_average_fuel_economy

Does that make a meaningful mileage difference or is it just a marketing trick because it’s so obvious to the user when the engine shuts off that “it must be saving fuel”.

During a normal 15 minute drive, the engine auto shutdown shaves maybe 20 seconds of runtime for me (smaller city without long lights) and it’s at the lowest engine consumption level (idle).

Given that an engine can idle for approx an hour on a gallon, I fail to see how an idle-off makes any meaningful difference for the average driver. It reeks of a marketing scam.

Read the person you are replying to. It doesn't matter if it is useless in real world. What matters is if it beats the tests created by govt bureaucrats.

>stop/start is estimated to boost fuel economy by 4 to 5 percent using the EPA test cycle

https://www.caranddriver.com/news/a19561461/automakers-incre...

It's not useless: a reduction in 4-5% of emissions in urban stop and go traffic would be huge for air quality and health. It likely won't do much if anything for total CO2 output but offloading the emissions to manufacturing of parts needed for extra maintenance (aka a far more efficient power plant in a less densely populated area) instead of driving can still be a net win.

Regardless, fuel efficiency standards have driven a significant amount of innovation even if this specific rule seems absurd from the outside.

Tests vs real world...

They should only do that after they have reached operational temperature. Turning off the engine while it's still cold (i.e. below operational temperature) wears a lot on it. This is why diesel is a bad choice, if your regular trips are short.

Idle stop always makes me wince. :S

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