Cost benefit analysis of shutting off at stoplights

Mike78 · #1 02-18-2009, 10:04 AM

I'm really an analytical numbers crunching kind of guy, so I love seeing how much money I save with minimal effort in my hypermiling-lite driving style. for the most part I follow the speed limit (maybe a little under for higher speed limits), coast down hills and up to red lights, go easy on acceleration and up hills, potential parking, and maybe a few other things but that's about it. With these simple things I have gone from typical mpg of 21-23 (old epa rating of 24 combined for the Maxima) to consistently 27-28 in winter and 29-30 in the summer (with A/C mind you). That's up to 43% better than the revised epa estimate - a number I am very happy with.

I occasionally try new things but have found most involve more work than I feel is worth it or are things that I feel are just plain unsafe and am unwilling to perform (I will not mention them to prevent the flame wars). One thing I thought was an easy one which I started doing was shutting off the engine at stoplights. It's really not that hard, but I've had second thoughts after crunching the numbers.

I drive 70 miles per day during the week, and about 50 miles total each weekend. Including monthly trips to visit family it comes to about 25,000 miles per year on the car. I have 4 starts per day on average, and I probably stop at red lights about 4 times a day. My GPH reading from the Scangauge at idle is .30; I've timed some lights and the average sit time is about a minute. Now I go through a starter (without hypermiling) about every 4-5 years. If I replace it myself it's about $150 for the part. But based on my scenario, if I turn the engine off an additional 4 times/day, I'm doubling the usage of the starter and cutting it's life in half. That's means instead of an amortized annual cost of $30 for the starter, it's now $60. $30 more per year. Let's go back to my cost savings. An average idle of 1 minute with .30 GPH at 4 times per day is .02 gallons saved per day. At a worst-case-yet of $4/gallon, that saves me 8 cents per day, or $29/year. At current gas prices it's less than half that. So I'm not even breaking even.

Now I guess you could look at the big picture of how many millions of barrels of petroleum we as a whole would save if everyone did this, but then you'd have to also consider the carbon footprint of the starter, and I'm starting to get into territory I'm unfamiliar with.

PaleMelanesian · #2 02-18-2009, 10:08 AM

Remember, though, that these are warm restarts. They likely wear the starter less than the first cold start.

Also, Wayne got nearly 100,000 miles out of his starter, with full-on hypermiling and many more starts than you're talking about.

JusBringIt · #3 02-18-2009, 10:28 AM

starters every 4-5 yrs seem to be a bit short life to me. If you pay $150 every 4 yrs, you are being sold short my friend.

Mike78 · #4 02-18-2009, 10:36 AM

Quote:

Originally Posted by JusBringIt

starters every 4-5 yrs seem to be a bit short life to me. If you pay $150 every 4 yrs, you are being sold short my friend.

I agree, but that is the Maxima (any other Maxima owners out there?). I replaced it myself late 2006 and the one I took off the car was not original, meaning it had already been replaced at least once. The car is a 2000 (likely sold in 1999). So I am guessing of course on the longevity, but I came up with 7 years divided by 2 starters = 3.5, plus some fudge factor assuming I may not be quite as rough on it as the prior owner, but then again the car was well maintained when we bought it. Do you know anywhere to get cheaper starters?

ksstathead · #5 02-18-2009, 10:48 AM

2000 Honda CRV 114K
2003 Toyota Tacoma 46K

No new starters. Not flat-towable, so only FAS occasionally while at or approaching long lights. Vast majority of starts are cold, including many of the FAS starts since I have only a 1.5 mile commute. Probably started the Tacoma over 100 times (warmed) while waiting 4.5 hours in a recent E-waste recycling line.

Mike78 · #6 02-18-2009, 10:57 AM

Quote:

Originally Posted by ksstathead;

Probably started the Tacoma over 100 times (warmed) while waiting 4.5 hours in a recent E-waste recycling line.

E-waste? Isn't that what that little recycle bin icon on your desktop is for?

ksstathead · #7 02-18-2009, 11:46 AM

Quote:

Originally Posted by Mike78

E-waste? Isn't that what that little recycle bin icon on your desktop is for?

Funny.

It was a long overdue effort by the county. 2500 cars (maybe that many more turned away), and over 1 million pounds of PCs monitors tvs, etc.

keep the heavy metals out of the landfills.

Psion · #8 02-18-2009, 10:56 AM

This is good to know, as I was a little concerned of how these types of restarts were affecting the life of my starter.
Sounds like I don't have much to worry about.

JusBringIt · #9 02-18-2009, 11:01 AM

For cheap replacement parts for anything I go to:
http://car-part.com.

Save it. I've gotten a replacement ecu for $70 on there. It's an international junkyard and you can get a starter for as little as $15 that will last say 40k miles hypermiling more or less depending on original miles. either ways, it'll save a lot of money.

ILAveo · #10 02-18-2009, 05:40 PM

Quote:

Originally Posted by Mike78

.... Now I go through a starter (without hypermiling) about every 4-5 years. . ....

.

It's hard to pin down that number. In 28 years of motoring (~500,000 miles?) mostly in older American cars with mileage at 50,000-200,000 I've only replaced one starter--21 years ago. From my admittedly limited data I'd guess that starters' expected design life is more than 200K miles. Maybe I've been lucky?