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Old 08-18-2013, 04:55 PM   #1 (permalink)
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Economics of hypermiling vs. vehicle longevity

So my brother-n-law recently visited and was asking some interesting questions about some of the techniques I use. He works at a lumber mill in Oregon, specifically he is a mill wright. So he professionally does maintenance on heavy duty machinery. He is not an apprentice, he is a fully certified mill wright. A lot of his questions center around diesels, but overlap to gasoline.

1) Grille blocks, engine heating in the summer, engine insulation. He claims that higher temperatures for longer times is reducing the lifetime of the engine. He says that the higher temperatures actually change the molecular composition and weakens the metal.

2) Running thinner lubrication. He says that thinner lubes essentially run like water, increasing friction. So this adds excessive heat, which due to thermal expansion increases friction again. All in all, greatly increases wear.

3) EOC. Wears out batteries, wears out starters, wears out cooling system, wears out engine.


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Old 08-18-2013, 05:37 PM   #2 (permalink)
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1. Grille blocks do increase engine compartment temperatures, relative to a non blocked grille. Higher sustained tempertures will cause gradual degradation of engine compartment components. Is the degradation significant? It depends on the climate and peak compartment temperatures. One reason I left the clutch fan on the Ranger was it increases engagement depending on the temp of coolant passing through the radiator as well as the fact that there are several other openings in the front of the truck that are not blocked. No problems with original radiator and coolant hoses and no loss of coolant at 16 years and 130 k miles, so in my case I'll keep the grille block.

2. Thinner lubricants actually flow faster and keep friction surfaces cooler due to increased flow volume. Also thinner lubricants require less energy to push through the lubrication passageways. Also, decades ago Ford reduced the maximum oil pressure to 35PSI by weakening the oil pressure relief valve spring tension. It was responsible for a .5 MPG increase in fuel mileage and after decades of seeing many modern engines hitting 3-400 K miles I can't agree with the rationale that you are increasing friction. Tolerances have been significantly reduced in the same time period. Nissan has used 4 different stock piston sizes as well as main and rod bearings. In other words there are 4 different sizes from the factory. They picked the sizes depending on the finsihed tolerances of the bores and main and con rod journals.

Bottom line is with modern manufacturing technology, thinner oils are part of the combination of improvements that have seen engine life quadruple in 50 years. The much higher SAE oil grades available today are another part of the total systematic improvements. I totally disagree with statement number two.

3. EOC will cause increased stress on some components. Catalytic converters suffer from increased heat cooling cycles. Sentra stopped using EOC when he found it was causing his emissions to increase dramatcially, to the point where testing showed long term effects (he is certainly free to add info, this is what I read from his posts). I don't believe EOC overstresses cooling systems. Obviously if you EOC enough to drain your battery if will shorten battery life, and if you use the starter more frequently, then, in my opinion you will reduce it's life expectancy. Repeated heat-cool events, beyond what is considered normal could also increase the accumulation of EGR-PCV deposits.

As far as higher temperatures causing metal deterioration, it must be understood that to get to that point you would have to be far in excess of designed operational temperatures, and if this was the case, then you would see significantly greater longevity of engines in colder climates. I think the opposite is true. in my opinion extremes of operational temperature are the principle cause of premature engine failure.

I don't use EOC myself.

regards Mech

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Old 08-18-2013, 05:43 PM   #3 (permalink)
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I also believe that your brother in law may be correct in his assumptions, probably based on his experience with heavy machinery in his work environment. That is a different type of environment compared to a modern passenger car engine.

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Old 08-18-2013, 06:15 PM   #4 (permalink)
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Originally Posted by Old Mechanic View Post
Obviously is you EOC enough to drain your battery if will shorten battery life

How does EOC affect the battery? If you EOC with headlights / heater etc. on I can see that, but I can't see an affect otherwise.
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Old 08-18-2013, 06:26 PM   #5 (permalink)
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Originally Posted by songman View Post
How does EOC affect the battery? If you EOC with headlights / heater etc. on I can see that, but I can't see an affect otherwise.
most people forget the fact that with manuals you can bump start the car. the starter takes alot of power to start the vehicle so as long as you bump start and have low electrical loads when off you would be fine

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Old 08-18-2013, 06:28 PM   #6 (permalink)
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The basic fact is that the less fuel you use per mile the less heat your engine generates per mile. It is quit posible that the engine bay temps may not rise due to upper grill blocking as much as due to drive faster and harder... viscosity alone is not the only thing affecting lubrication. one of the major causes of wear is load...
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Old 08-18-2013, 09:10 PM   #7 (permalink)
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I'm still quite skeptical to full grille blocks, but EOC doesn't seem to harm the engine so much. Also, many newer engines are getting the catalytic converter assembled in the exhaust manifold to get heated quickly, reducing the emissions at the cold phase.
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Old 08-18-2013, 09:31 PM   #8 (permalink)
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I've been giving some thought to this recently.

If engine compartment temperatures are increased, it must shorten the life of the accessory drive belts and timing belt and possibly battery. Maybe even the cooling system hoses.

My biggest concern is with neutral coast, whether EOC or idle, which shocks the driveline if you don't rev match perfectly or slips the clutch if you feed it in, all in the reverse direction to that which the transmission is designed for.

Starters, yes, if you use them with EOC.

Most engine wear is supposed to occur on start up so if the engine is constantly being switched on and off that may increase wear. On the other hand, the engine is at operating temperature and the oil hasn't drained away from the top of the engine, so it won't be as bad as a cold start.

Lower oil viscosity, within the grades specified by the manufacturer won't hurt the engine. Outside that? Any extra friction/wear should manifest in worse fuel consumption so that's probably not an issue.

Unless the engine is overheated the metal structure won't change.

I think it's more a possibility than reality but if you operate a vehicle in a manner other than it was designed for there is a risk of shortening component life.
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Old 08-18-2013, 10:23 PM   #9 (permalink)
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The heat will not cause the metal to weaken, steel has to be heated beyond its recrystalization temp of roughly 900 degrees before it can be annealed.... good luck getting those temps anywhere but the exhaust. Aluminum is around 500 degrees iirc, again, not happening in a water cooled engine. Will plastics get weakened and crack? Sure, but the plastics under the hood are designed to get hot and many are thermosetting plastics meaning they won't deform under heat, excess heat beyond its setting temperature will cause charring but because it doesn't melt no fire.

If the engine is within a safe temp range, up to 225 degrees for mine, no problems.

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Old 08-18-2013, 11:44 PM   #10 (permalink)
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I considered all these issues when I first started reading this site. My take is that a car will generally be most reliable when temperatures and stresses are equal to or less than those in the stock configuration. That means:
1) No full grill blocks for me, I would consider up to 50% based on local climate and driving pattern.. I would prefer to keep the engine compartment cool and prolong the life of my rubber and plastic parts.

2) Thinner lubes are actually called for an approved for some engines. As long as they pass certification for the oil standard recommended, there is no problem. I use oil of the weight recommended by the manufacturer and which exceeds the requirements. In the case of heavy diesel equipment not rated for thin oil, you might indeed observe an increase in metals in a UOA with thin oils.

3) EOC is something I can't do in my car, since it would cause my turbo to melt. However, I wouldn't do it even if I could, regardless of the payoff in fuel mileage. Not only do I consider it a safety hazard, to me it presents occasion for unnecessary wear on accessories like the clutch, starter, battery, etc. Totally not worth it.

4) The temperatures we're talking about here won't cause the iron atom lattice to expand enough for their alloyed state to alter. Perhaps with huge industrial equipment that is different.

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