Tuesday, July 12, 2011

Good automotive news

Apparently, Chevrolet is going to join VW, Mercedes, and BMW and produce a diesel powered compact sedan, hopefully to achieve approximately 50mpg on the highway, far better than the ordinary 36mpg highway achieved by the gasoline powered Cruze.

OK, so how does this pan out for the consumer?  Well, as one who is currently driving a 12 year old minivan with about 225,000 miles on it, I'm guessing that even domestics can achieve 300,000 miles and 15 years if well cared for.  So I generated a little spreadsheet to calculate what would be saved given a vehicle life of 300k/15 years, gas/diesel price of $4/gallon, 5% interest lost on the extra price of the diesel, 35% added efficiency, and $5000-$7000 extra for the diesel engine.  The extra cost is estimated from the surcharge for the VW Jetta ($5k) and the Silverado 3/4 ton ($7k), though it might be lower for the Cruze.

End result?  Monetary savings start when you drive about four times as many miles as the extra cost for the diesel--20k miles/year if it's $5000, for example.  For a minivan with ordinary mileage of 22mpg, you need to drive 2.5 times as many miles as the extra cost--12,500 miles to break even with a $5000 diesel.  For ordinary drivers, it looks like a $3000 option would help them break even given typical use of a compact vehicle. 

Note as well that not even this--a compact car with a diesel engine--meets the fuel economy standards envisioned by the Obama administration.  In terms of science and engineering, this should be a nonstarter.  But again, physics and economics don't seem to mean much to politicians, sad to say.

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