Quote:
Originally Posted by MetroMPG
An electrical engineer who routinely tracks the calculated MPG of his 2013 Prius noticed a significant drop in efficiency following a recall (software change) meant to fix a problem with overheating inverters in the cars. |
An apparent drop of 5mpg may be related to any number of things. What was the weather like? Traffic? Did his commute change? Did he start going to a closer grocery store that didn't allow the engine to warm up fully? Did his car develop an undiagnosed dragging brake caliper? Does his car have a clogged EGR? Has his PCV valve stuck? Does he use AC or heat more now than he used to? Any of these things could explain a change in fuel economy as drastic as he claims. Then there's the issue of the claim itself: 49 to 44 over how many tanks? How consistently? How meticulous are his records? Is this claim accurate or an estimate?
As an illustration of a possible counterargument, after I had the recall performed in early April 2014, I had a run of 9 tanks in a row at 60+ mpg, then one 59 mpg, then 6 more 60+, through October of that year. Using Enger's reasoning, the recall improved my car's fuel economy drastically! Except it didn't, because we haven't controlled any variables except the software update, so we have no way of knowing what effect it has on fuel economy by itself.
Quote:
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The Prius has an EPA fuel economy rating of 51 miles per gallon in city driving for the 2010 model and 49 mpg for the 2014 model. Enger said his city driving mileage dropped from 49 mpg before the software change to 44 mpg afterward.
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This is a deliberately misleading statement: the 2014 is rated 49 mpg city because the EPA approved a new correction factor last year applying to 2011-2016 vehicles, leaving the 2010 with the original rating.
I don't know who's right here, but Enger has a lot to prove before I believe his claims.