While reading an incredible long article (more like a book) I came across a page that has some interesting information where EPA numbers come from and figured I would share it here.
Car Bibles : The Fuel and Engine
According to this, we should all feel much better about our % over EPA numbers. Especially if you own a vehicle build before 2008 because our true EPA numbers should be much lower then they are, once all factors are considered. So my REAL EPA (due to inaccurate testing) should be closer to 24.4mpg combined, instead of 28mpg. If this is true then the 41.6% over EPA I got on my last tank (personal best btw) would actually be 54.6% over EPA if adjusted to today's EPA standards.
Quote:
EPA TESTING PROCEDURES
Congress and car company lobbyists required the EPA to measure mpg figures using the following simulated real world conditions in a lab. That's right - EPA testing happens on a dyno in a lab, not on the open road.
Average highway speed : 49mph
Maximum highway speed : 60mph
Temperature : 75°F
No rapid acceleration
No air conditioning
No passengers
No rough roads
No hills
No wind
No low tyre pressures
No ethanol in gas
The first problem is the last point : no ethanol in gas. In America, it's almost impossible to buy zero-ethanol petrol - it's all E-10 (see E10 elsewhere) so you're already going to be down 5% on the EPA figures even if you could meet all the other requirements.
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I also learned that the EPA ratings for European cars are higher (probably due to US NOx standards) meaning if you own a European car you probably won't get as much over EPA (if you do, you're awesome!) as you would with the same car in the US. The bar is already set higher, leaving less room for improvement.