[bestclimb]

To evaluate the economics lets start with what we can save then compare it to what it costs.

In 100,000 miles of driving and getting 30mpg you spend about $13,333 in fuel. (at an average of about $4 per gallon

If you hypermile and increase your mileage;
at 35 you spend $11428
at 40 you spend $10000

If you get 33% over EPA which pretty easy to do looking at some fuel logs and by personal experience, the maintenance costs would have to be $3,333 more.

With reduced wear on tires and brakes you would have so see a significant increase in wear for it to not be cost effective.

1) Higher temps does weaken metal but the effect is not significant till you getting into the 300-400 f levels when strength of aluminum really drops off dramatically. (this is one of the reasons piston aircraft CHT temp red lines are set where they are). A water cooled engine would boil over well before then. The only time I ever saw elevated temps was climbing on an unseasonably warm day with a full grill block, mea culpa, trimmed open my grill block and the problem was solved.

2)Thinner oils do not increase friction, they do decrease the oil film thickness which may allow particles suspended in the oil to cause wear (a bit of material contacting both surfaces at the same time). keep your oil clean and think long and hard if you are considering using thinner than recommended. Using a too thin oil can cause problems if the oil won't stay on bearings due to loose tolerances or low pressure, so don't use thin oil if it is a concern as it's benefit is small.

3) They say most wear happens at start up, which is true at cold starts, as oil pressure is not up and oil has dripped off parts, no oil film and loose tolerances due to cold parts causing wear (thinner oil can help if it will stay where needed by getting to parts quicker) A warm start does the same amount of wear as would have happened while idling for the same amount of time as the start (possibly a net of reduction of wear)

As to wear on the starter, meh, we would have to go through quite a few starters to cut into the fuel savings, in my experience it just ain't happening and I think a lot of other people have a similar experiences.

How would starting and stopping wear on a cooling system, that makes no sense to me.

Since I started hypermiling my batteries have lasted about as long, the cold and inactivity have been harder on them than an increased number of starts (which is minimal due to bump starts)

Clutch wear may be a concern but a bump start is easier on a clutch than a big down shift without rev matching and I see and hear people do that all the time. There are also examples of people hypermiling a couple hundred thousand miles on a clutch. If it were causing a problem we could be hearing about it.