I’ve never understood why they want us to slow down so much.  I’m not talking about massive speeding, but lowering the speed limit to 55 doesn’t seem to make much sense.  Now with all the “global warming” nonsense, they are using “save fuel and money” as the incentive.

I’m a little ridiculous when it comes to cars.  I track all my fill ups, etc.  Yeah…I know…it’s silly…but I do it anyway.  So let’s see what the ACTUAL numbers say:

On my 2001 Corvette with a big Chevy 350 ci engine, I get an average mixed mileage of 20.5 MPG.  Clean on the highway at 70-80 I get a good 29-32 MPG.  The day I bought it and drove back to Texas, I drove 490.3 miles on the highway on the first tank of gas.  Took 16.858 gallons.  Yes, that it 29.08 MPG in my big Chevy Corvette.  So, tracking the numbers for a few years, this is what I get:

There are a few outliers, but I think the trend is obvious.  It appears that the faster I go, the better fuel efficiency I get.  I don’t have data where my AVERAGE speed is above 55, so I have to extrapolate.  But based on a few single tanks of total highway driving, it seems to be consistent.

Now, my 2010 Volkswagen Jetta TDI diesel is a much smaller 2 liter engine.  The car is geared very differently, and I haven’t had it long enough to get a large amount of data.  But with an average speed of 40 MPH, I get an average fuel consumption of 38.06 MPG.  Again, a highway trip of almost total highway miles gives an average speed of 54 MPH, and an efficiency of 43 MPG.

It seems as my own “Mythbusters” results are pretty clear.  The faster I drive, the better fuel efficiency I get.  Not just on the Corvette, but the VW Jetta TDI also.

Notes

Yes, I’m sure there is a point of diminishing returns.  I have no reason to suspect that point is 55 MPH as is advertised by governments and global warming conspiracy theorists.  Based on my own driving patterns and measurements, the point of diminishing returns is above 75.

I also understand the the onboard computers do not measure actual fuel efficiency, but instead estimate efficiency based on measured airflow.  It should be noted that I do not use the computer estimates, but instead measure the exact amount of fuel used and the exact miles driven.  How do I do that?  When I fill my tank, I know how many gallons I put in.  There is no estimate.  The pump says the tank to 16 gallons.  The odometer of the car tracks how many miles I’ve gone since the last fill-up.  Using those two numbers, I get an accurate fuel consumption measurement.

But it does bring up an interesting point.  How different is the computer air measurement estimate from the measured calculations.  Let’s see:

It seems that the Corvette DIC (Driver Information Center) over estimates the fuel efficiency.

It seems the VW Jetta TDI computer also slightly over estimates the actual efficiency.

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