We're all familiar with the effects of temperature on fuel economy. you may have also heard that smooth roads produce better numbers than bumpy ones. concrete's better than asphalt, etc.
I've often wondered what impact a wet road has on fuel consumption. the most obvious drag you feel is when you hit a deep patch of standing water, but there must also be a continuous low-level drag as the tires "part" the water and throw a constant spray behind them. (not to mention the added electrical load of lights & wipers if it's raining.)
I've looked around a few times for info on this, and have only come up with one page.
The claims are pretty astounding - with the result that i'm somewhat skeptical. but I haven't found any competing information on which to base (or reduce) my skepticism.
The claim is:
Quote:
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How about Rain; will it hurt my mileage? The first screenshot shows a baseline with no Rain. [With] 'Light Rain' [...] we see the MPG has dropped from 47.69 to 40.77 MPG. (source)
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That's
a mileage drop of 14.5% in the wet. The calculation is for a Prius at 65 mph at 37F.
(Note: this is a calculation, not an observed/tested result. but I've read quite a bit on this guy's site (prius aficionado), and he's clearly on the ball. the calculation is from a complex palm application that calculates energy use based on a multitude of adjustable variables.).