My first thought on this technique was accelerated wear of the starter.
I was really excited about this technique cause it sounds like it has lots of potential more then a lot of things I've read. Esp. if where talking about long strecthes of road or hills. Unfortunately I have a turbo on my car and shutting off the engine like this is a no, no on turbocharged vehicles.
well, I know that oil is multiviscosity so the oil can more easily flow through the engine when its cold. but that's just when its cold and it makes oil thicker. I'm sure oil would have no problem doing this with the car at operating temp. you always hear not letting the car warm up before you drive accelerates wears. but where talking about it being warm.
I think the result would be worn out starter, batteries, etc. and not so much the engine. but thats not really an issue since that stuff is lifetime warrantied. and autoparts stores are really good about honoring there warranties on such items.
First, let me alleviate some of your fears about hot turbos and shutdown: While you are technically correct that immediate shutdown can damage the bearings in the turbo, for the most part that only applies after heavy use. During normal easy commuting, there is not enough heat buildup in the turbine housing to damage the oil. After driving hard however, the turbine housing can be glowing hot. In other words, the amount of heat it must deal with goes up proportionally to the amount of loading. So if all you are doing is taking it easy on surface streets, the turbo is unlikely to be much warmer than if you were to just let it sit there idling. The only way to be sure however would be to measure it, so don't take my word for it.
Another thing worth noting is whether your turbo is water cooled or not. If it is water cooled, you have even less reason to worry. Convection through the cooling system will continue to provide a fresh flow of coolant even with the motor off, and this will keep bearing temps well below where the oil is damaged.
And the one last point worth noting is that synthetic oil is far more tolerant to heat. When dino oil cokes up, the synthetic hasn't even gotten close to it's breakdown temperature.
So in a nutshell, my view on EOCing with a turbo is that it's probably ok, so long as you aren't doing it on the highway or immediately after driving at high speed and or high load. But I'm not guaranteeing anything! :P
As for the extra wear, I don't think we are getting something for nothing here. It's a tradeoff no doubt.
The turbo has the ability to be water cooled but It's not, cause of the extra lines and even more so cluttering of my engine bay (need to really work on cleaning up my engine bay). but it would be well worth doing.
a temp gauge on the turbo would be awesome :-) .
your probably right though cause it states in this book at it only take 1000 yards or 1 minute to cool down an a turbo after "high output use" . driving for mileage and doing 60 on the highway is definately not hight ouput use. it also doesn't say if your using synthetic or water cooled.
I dunno, I've been messing around with this a little. using it on my commutes. finding places where its actually worth it, etc. but my half a tank is looking pretty bad. I haven't really given it a whole tank. but the gas is going down pretty bad on almost a complete half tank.
Do some cars not respond well to this or is everybody else getting great mileage with this technique???
Well to paraphrase something said in another thread, if you only spend 5% of your time EOC'ing, that only accounts for a saving of 5% at your lowest fuel consumption which isn't really a heck of allot. E.g.:
Assume your idle fuel consumption is .3 GPH, but you burn 1.5 GPH at 60 mph. In one hour, assuming you spend 5% of your time idling, your overall average consumption is .015 gallons at idle, plus 1.425 gallons at speed, for a total of 1.44 GPH. Converting that idle time to EOC time, it drops just the .015 gallons to 1.425, or 98.96% of your normal consumption.
So in this example for a car that could get as much as 40 mpg without EOC'ing, one might see as much as 40.4 mpg using EOC'ing just 5% of the time.
Obviously this oversimplifies the math, but there ya go. Factors that will skew the numbers better or worse are of course the percentage of EOC'ing, and the rate of fuel consumption at idle.
That said, I think there are better ways to save a gallon of fuel without the extra wear and tear - even though it took me until just now to really figure that one out. Certainly there are conditions however where EOC'ing can provide substantial gains in FE such as while descending a long grade, but around town on the flats, it's going to be minimal.