Did some math. I think you will find this interesting.

[Fat Charlie]

Yahoo practices its usual stellar journalism. I had expected better than base fearmongering from Popular Mechanics, though.

There are those who refuse to be shaken from the practice of coasting downhill in neutral to save gas. This is a bad idea no matter how you look at it. Let's set aside fuel economy for a moment. Coasting downhill in neutral is illegal in most states. And it's dangerous in all states. In neutral, you have no way to accelerate to avoid a hazard, and if the engine stalls, you have no power steering or vacuum boost for the brakes. If the hill is steep enough to call for hitting the brakes to keep you from gaining speed, they're more likely to overheat—and overheated brakes lose effectiveness until they cool off. They'll probably do that right around the time the police show up to take the accident report.

Here's the surprise: There's no trade-off between safety and fuel economy in this case. Leaving the car in gear while coasting downhill actually is more efficient. Why? Blah, blah, blah DFCO ...the engine consumes no fuel at all while the vehicle is coasting downhill.

In contrast... idling in neutral down a ½-mile-long hill consumes fuel for 30 seconds, for a total of about 0.32 ounces of gas. Popping the car into neutral actually wastes gas.

This may seem counter-intuitive, but that's what data are for—replacing good guesses with solid facts. Watch the data, and over time the savings will take care of itself.

So let me get this straight, Popular Mechanics: If my engine stalls, my car won't work well and that's dangerous at speed. Of course if my brakes do happen to work while my engine is stalled they'll overheat and kill me. Which they won't do if the engine is running because the brake booster acts to cool the pads, right?

I'm sure that a search of Popular Mechanics will show at least one or two solid facts about engine braking. Nice job, guys, and thank you so much Yahoo, for giving this crap a wider audience. Yes, it's good to put out the word that people can save a lot of gas on their own. It's better to hire a writer and do some research.

[user removed]

Jesus, if I am coasting downhill in neutral, I would use a downshift to control my speed if it became excessive. Pick the gear to maintain the desired speed.

Back when most of the laws were written, the Plymouth's with freewheeling had mediocre synchronizers at best if at all. The freewheeling had to be engaged or disengaged when the vehicle was stationary, and the brakes were very marginal at best.

Combine that with Route 33 or 50 east through the mountains of Virginia and West Virginia and you have the recipe for a disaster.

These days you can downshift your Honda into 5th, 4th, or even 3rd at 70 MPH down a 7% grade, or just slam on the brakes. Even without either of those options your steering and handling would be light years better than the old mid 30s sedan.

regards
Mech

[Frank Lee]

I'm trying to remember the last time I had to accelerate out of a potentially bad situation, especially one going downhill. Ummm.... nope, none in the last 30 years anyway.

[Frank Lee]

Originally Posted by cleanspeed1

Because it didn't matter much back then to most people. You know things are changing when today's Yahoo page brings about hypermiling techniques as an article.

It mattered in the '30s, then the '40s, then the '70s, then the '80s, then today.

Inbetween people forgot all about it.

So what's the tipping point?

Probably not dollars/gallon. Not when you see people filling up at a station that's 20 cents/gal higher than another station 2 blocks down the street.

Probably not Peak Oil. That's been known since the '70s and we all know how consumption has been between then and now.

Must be percentage of household budget. Say, 1000/mo total budget, 200 of it for fuel? Doesn't really matter if fuel is $1/g or $4/g, the household will adjust miles driven and fe of vehicles used to consume that 200 no matter what? Yes, I think that is it.

[euromodder]

Originally Posted by Frank Lee

I'm trying to remember the last time I had to accelerate out of a potentially bad situation, especially one going downhill. Ummm.... nope, none in the last 30 years anyway.

When riding my motorcycle, more throttle was a very common technique of getting out of dangerous situations.
It works far better with a MC than with a car.

Originally Posted by PopMech

Leaving the car in gear while coasting downhill actually is more efficient. Why? Blah, blah, blah DFCO ...the engine consumes no fuel at all while the vehicle is coasting downhill.

All depends on the gradient.
If it's that steep that you need to use engine braking to prevent a runaway, DFCO is fine.

If it's not so steep, it may well be enough to coast downhill using no gas at all (EoffC) or very little (EonC) without developing into a runaway - aero drag will control your speed. Well, maybe not for basjoos

[skyking]

Congrats Dunkler!
Regarding the quoted article:
"If the engine stalls", how quaint. Last time that happened in a car I had, it was my Camry and the timing belt had broken. I PUT it in neutral and coasted into a handy parking spot from about 40 MPH.

[beatr911]

Getting back to the math

Originally Posted by Dunkler

I love you guys! Ok, I will be open with you fellas. I paid $9,900 for this 2007 Honda Fit. Interest rate at 4.99%. It only had 65k miles on it when I bought it. Now it has 68k (give or take). Full coverage on the Fit is $40/mo. I carried liability only on the F150 and it was $23/mo.

SO, do more maths and figure out when the car will pay for itself!

I forgot the net present value calulations from school so lets make it simple. We're assuming the F150 is parked along side the house and not sold. Any finance types out there please correct the math. Say that $9900 purchase price x 4.99% interest per year is $494/year interest. Say it's for 4 years so $494 x 4 = $1976, add the original $9900 and its $11876 total purchase. Adding the difference in insurance $17/month over the same 4 years is $816 so a cost of aquisition is $11876 + $816 = $12692 over 4 years. Assume after 4 years that the Fit insurance will revert liability only once the 4 year loan is paid off and will be $23/mo like the F150.

After year 4 when the Fit is paid off and the insurance rate drops we'll assume the cost to own the Fit is the same as the F150. Note that the Fit will be cheaper on maintenance and repair but we don't have numbers to assign to that savings.

Now, the cost of the Fit over 4 years = $12962 divided by the estimated savings based on 12000 miles of driving per year at $1450.80 works out to 8.9 years to break even.

Since the insurance will continue after the 4 year period, (but drop by $17 after year 4) it's more like 9 years.

If the F150 was sold for $3000 the $12962 initial 4 year cost drops to $9962. $9962/$1450.80 per year fuel savings = 6.8 years to break even.

Also as mentioned, the cost to maintain will be much less on the Fit so that will further reduce the break even period, but we don't know by how much. It's probably safe to say though that the Fit will begin to payoff at about 6 years or so if fuel prices stay the same.

This exercise shows that spending money on a vehicle to save fuel makes sense, but only if you are going from a blatant FSP to a real miser. Cost to purchase a vehicle can pay for alot of gas and could make the purchase folly if not done properly. It seems to make the most sense if you are about ready to replace your vehicle anyway and/or drive alot of miles and expect to keep the vehicle for a long time.

[kir_kenix]

Originally Posted by beatr911

Getting back to the math



I forgot the net present value calulations from school so lets make it simple. We're assuming the F150 is parked along side the house and not sold. Any finance types out there please correct the math. Say that $9900 purchase price x 4.99% interest per year is $494/year interest. Say it's for 4 years so $494 x 4 = $1976, add the original $9900 and its $11876 total purchase. Adding the difference in insurance $17/month over the same 4 years is $816 so a cost of aquisition is $11876 + $816 = $12692 over 4 years. Assume after 4 years that the Fit insurance will revert liability only once the 4 year loan is paid off and will be $23/mo like the F150.

After year 4 when the Fit is paid off and the insurance rate drops we'll assume the cost to own the Fit is the same as the F150. Note that the Fit will be cheaper on maintenance and repair but we don't have numbers to assign to that savings.

Now, the cost of the Fit over 4 years = $12962 divided by the estimated savings based on 12000 miles of driving per year at $1450.80 works out to 8.9 years to break even.

Since the insurance will continue after the 4 year period, (but drop by $17 after year 4) it's more like 9 years.

If the F150 was sold for $3000 the $12962 initial 4 year cost drops to $9962. $9962/$1450.80 per year fuel savings = 6.8 years to break even.

Also as mentioned, the cost to maintain will be much less on the Fit so that will further reduce the break even period, but we don't know by how much. It's probably safe to say though that the Fit will begin to payoff at about 6 years or so if fuel prices stay the same.

This exercise shows that spending money on a vehicle to save fuel makes sense, but only if you are going from a blatant FSP to a real miser. Cost to purchase a vehicle can pay for alot of gas and could make the purchase folly if not done properly. It seems to make the most sense if you are about ready to replace your vehicle anyway and/or drive alot of miles and expect to keep the vehicle for a long time.

This is almost the exact same calculations that I went through myelf not too long ago. I decided that it was cost effective for me to drive my present DD into the ground before buying another, slightly more fuel effecient one. But like beatr has said, if its time to trade in anyway....

I imagine that you will save enough on the low mileage fit in maintenance costs (oil, tires, etc) to offset several thousand dollars against the (presumably) high mileage f150 (more frequent and more expensive tires, oil, expences associated with a high mileage truck etc). I wouldn't be suprised at all if your payoff turned ito something like 5 to 5.5 years.

[Dunkler]

This exercise shows that spending money on a vehicle to save fuel makes sense, but only if you are going from a blatant FSP to a real miser.

Yeah, that's exactly what I did. I guess there was a lot more that went into this decision than I let on. My wife and I have a little boy right at a year old. Sometimes I need to transport the little bugger and the single cab Ford pickup was not conducive to that at all. Also the F150, although it was a good truck, it did leak oil and coolant. I usually had to add 2-3 quarts between each oil change and top off the coolant once or twice. Not to mention the F150 had nearly 200k miles on the clock!

[SoobieOut]

I would rather write a program to do the math, but in this case Edmunds has a great website calculator that figure True Cost of Ownership.

2009 Honda Fit 1.5L 4-cyl. 5-speed Automatic True Cost to Own