Fun with Hypermiling - Part 6

Part 1 - Introduction - "What is Hypermiling?"
Part 2 - Test Hypotheses
Part 3 - Fun with air filters
Part 4 - We're talking tires
Part 5 - Driving Techniques
Part 6 - Is it worth it? 


So given everything that we've done, we should appreciate an annual fuel savings of $238.98. Sounds pretty good, huh? Free money, right in your pocket.

But here's where it gets really interesting.

While better fuel economy is great, the focus of my experiment was to see if the increased fuel economy is a good trade off for the wear and tear on the other items in your car that are being worn out faster by utilizing hypermiling techniques. I think it's something that all the "engineers" aren't accounting for in their reports.

Specifically, I'm thinking that with the increased tire pressure, the tires will bulge in the middle and wear out faster. When the car is put in neutral, it's using wear and tear on the throwout bearing, clutch, and transmission synchros. And when the car is shut off and restarted, there's additional wear and tear on the ignition switch, starter motor and the flywheel.

Figuring I'd keep this car about 10 years, this means that over the lifetime of the car, I'd save $2,389.80.
Being realistic, you'll need to replace the following items over the course of 10 years: tires, battery, clutch/flywheel, and starter. Conservatively figuring the car will see 15k miles per year, that's 150k miles over 10 years.

So if you owned a '94 Toyota Corolla like mine, here's how it breaks down, assuming you do the work yourself (tires are estimated, other parts prices taken from Advanced Auto online web store):

- Tires are about $320 (4 x $80) every 50k miles, so figure $960.
- One clutch - $40
- Starter - $107-$200
- battery - $60-$86

This is figured based on normal usage, so figure just for these four items, you're spending at least $1,167. This doesn't include labor to install them, and it does not include other items that may be required to be done (like flywheel resurfacing or throwout bearings for clutch jobs).

Once you start hypermiling, the wear on these items goes up considerably. For example, when driving to and from work, I would typically use the starter twice. By hypermiling, I was using the starter about 16 times. Every time the car starts, the clutch must be engaged, so that is 16 more times than normal that the clutch gets engaged. Also, as I coast in neutral, I engage the clutch to shift out of gear, then engage it again to get the car back into gear when I am done coasting. This accounts for at least 50 extra engagement/disengagement cycles. Sound like a lot? On a typical commute, I once counted 156 gear changes, just on the way to work.

Also, every time I shut the car off at a traffic light, I put a draw on the battery for things like brake lights, the radio, and then call upon the battery again to turn the starter motor. This puts additional strain on the battery, and could cause it to fail earlier in its life cycle.

I'm also overinflating the tires, so I'm putting undue wear on the center of the tread, and wearing them at a much faster rate.

So if all of these (except the tires) will expectedly wear out over the next 150,000 miles, by increasing their usage by at least 8 times their normal daily use, it stands to reason they will wear out that much faster. So, for example, instead of lasting 150k miles, they may last 20k miles. So your $107 investment in your starter just turned into a $749 investment in 7 additional starters.

And that $1,167 expense is now $2,616, which doesn't account for the increased (and unknown) extra wear on the tires which could equate to a few extra sets over that 10-year period.

So by Hypermiling, you might save $2,389.80 in fuel, but you'll spend at least $226.20 more to replace the parts that are now wearing out at a much faster rate. And that's if you buy the parts and install them yourself - your mechanic's labor fee is probably $85 an hour.

Based on the rough data, it appears that hypermiling would probably pay off if you were keeping your car for a short time (like a lease), or if you had an extended bumper-to-bumper warranty that would pay for the extra starters, clutches, etc.

Overall, I'm disappointed in the end result. I was hoping for a lot more mileage (at least breaking 40mpg) for my diligence.

On the positive side of things, I helped the environment by cutting my emissions at idle (traffic lights and coasting), I saved myself a few bucks worth of fuel, and by coasting, I learned a lot about how to take corners fast by carrying speed and not losing momentum. I was also VERY focused on every aspect of driving the car, and got better at planning maneuvers.

On the down side, it was boring (and mostly stressful) to drive so slow and methodically, and not really at a comfortable pace. The higher pressure in the tires also makes for some tricky driving under braking and on wet roads.

So it's back to normal, relaxing driving for me. It may not get me the highest mileage, but it's still respectable mpg and is exponentially less stressful!


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