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2016 MDX Adv/Ent

Does Auto Engine Idle Stop really save gas? It's not exactly smooth when I take the foot off the brake to restart every time as there's slight cranking. I thought you waste the most gas when starting the car and I don't see how this feature is helpful. Any thoughts?
 

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Because of the stricter EPA standards for gas economy, we are being attacked with a barrage of technologies that give small increment improvements. Examples are the 9 speed transmission, the idle stop feature, super thin oil, and the low-voltage alternator operation. Even the brake pads have spreader springs to make sure that there is absolute minimum drag. Each feature by itself is of little significance, but taken together can add one or two MPG to the EPA rating.

Adoption of the Direct Injection engine design gave a substantial increase in MPG. The HCCI engine design would be the next step in gasoline engine evolution. Mazda plans to use it in some 2018 model vehicles.

http://www.digitaltrends.com/cars/mazda-planning-hcci-engine-report-says/
 

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Well, it all depends on your commute. If you are crawling in heavy highway traffic or waiting at intersections, it for sure will boost your mpg. If you are like me and just have a long commute on surface streets and back roads without much waiting, than I doubt it will increase mpg by much.

Unfortunately, driving distances at constant 35-45 mph is not very efficient and there aren't many solutions for that.
 

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I don´t think the 9 Speed was installed for MPGs but rather to keep the MDX competitive with an underpowered engine for the Segment... That thing can do 0 to 60 in 6 seconds for Christ sake, MPGs be damned!
 

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Hugely Exaggerated Fuel Savings on Auto Idle Stop

Facts:
1) All stops under 10 seconds waste gas. [I can't post links in this forum yet]
2) An MDX probably burns about 0.25 gallons per hour idling with no load. [Again, I have a link but can't post]
3) If an average stop lasts 30 seconds, and restarting consumes 10 seconds worth of gas, you're saving 20 seconds worth of gas at each stop.

So how many stops does this feature have to make to save a gallon of gas?

1) At 0.25 gallons per hour, you must save 4 hours of idling to save one gallon of gas. At 20 seconds per stop, that would require 720 stops to save a gallon of gas.

PS: Don't believe the ecozealot websites that claim your car burns a gallon per hour idling. Only tractor-trailer rigs do that.
 

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I think the obvious answer is 'yes - idle stop saves gas under average conditions'. I say 'obvious' because if it wasn't true I don't think it'd be designed into the vehicle. The only other reason to design it in would be for marketing reasons but I don't think the feature is exactly warmly welcomed or sought by most buyers.

The word 'average' is key - some will experience no savings (such as when it never kicks in) and some will experience some obvious savings - when sitting at a long light, sitting in the fast food drive thru lane, sitting in a traffic jam.

I actually first experienced idle stop technology decades ago in Switzerland where it was a requirement of some kind when I was there. I thought it was pretty strange but one of the reasons was to cut down on pollutants - especially if stuck in a tunnel or indoor parking garage.

I don't think modern vehicles use a lot of extra fuel to start versus idle - I think the engine is smart enough to put just the right amount of fuel into the vehicle needed to start - it's not the same as decades ago when one needed to pump the gas somewhat to get the car started and in fact, one isn't supposed to put the foot on the gas pedal at all when starting nowadays. Engines have come a long way.
 

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Facts:
1) All stops under 10 seconds waste gas. [I can't post links in this forum yet]
2) An MDX probably burns about 0.25 gallons per hour idling with no load. [Again, I have a link but can't post]
3) If an average stop lasts 30 seconds, and restarting consumes 10 seconds worth of gas, you're saving 20 seconds worth of gas at each stop.

So how many stops does this feature have to make to save a gallon of gas?

1) At 0.25 gallons per hour, you must save 4 hours of idling to save one gallon of gas. At 20 seconds per stop, that would require 720 stops to save a gallon of gas.

PS: Don't believe the ecozealot websites that claim your car burns a gallon per hour idling. Only tractor-trailer rigs do that.
You could do that in 2 round trips to downtown Chicago. I don't have it on my MDX. But on my other car,I have it off all the time. Of course it's going to save gas. I don't think starting a fuel injection car uses more gas. Except when the car is cold.
 

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At 20 seconds per stop, that would require 720 stops to save a gallon of gas.
So 720 restarts for $3 savings? Yeah no thanks. We're saving incremental volumes of fuel but shifting costs to the consumer in other ways that the tiny fuel savings will NEVER overcome at current fuel prices. We can start with the development and hardware costs of this asinine concept. Then the increased wear-and-tear on the starter...oh I know its more robust than an average unit, which will make replacement costs double the average when it fails. Then the battery is being taxed all day long and the alternator leaned on relentlessly to keep it topped up. This is like the late 1970's when they were trying to figure out smog equipment, eventually we'll make progress. For the time being or until gas is $15/gallon, my MDX has two start buttons as others have noted.
 
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