Dash instrumentation has become more and more precise over the years.  Complex, informative data can be displayed with near pinpoint accuracy.  Digital readouts have become commonplace in everyday automobiles over the past decade.  Engine temperatures can be observed to the single degree as can speed, engine RPM, manifold pressure, boost pressure, transmission temperature and much more.  In the average vehicle, these multitude of real time data information readings are of little value. In most cases “Idiot Lights” would probably suffice.

However, for large vehicles, like heavy motor homes and truck trailer combinations, this information can be vital and of great value.  Observing various data trends and digital readout behavior while travelling, can reveal issues that require attention.  That attention may necessitate an operation strategy change, or, if necessary, a physical investigation.

But, there is one instrument that every vehicle has and is used daily.  It has not really evolved operationally over that available when we were born.  While some sensor changes have been made, it is still about as inaccurate as they were 30 years or more ago.  That instrument is the fuel gauge.

All vehicles seem to have the same inaccurate tendency.  It stays on “Full” for many miles after topping it up, then, finally starts to drop. This is understandable given the float is held to the tank roof until enough fuel is removed.  The reading is then steadily decreasing until it gets below half full. The decent then increases speed, not proportionally, seemingly twice as fast.  Soon the need for fuel goes from soon to now!

This is an irritation if you are driving a car.  You can usually easily get to a fuel station, even in very rural areas, on the couple of remaining gallons.   Not so with a large rig.  Two gallons might only get you 12 miles or so.  Adding to the inaccuracy of the displayed fuel level is the unknown, burnable fuel level?  How much fuel is unburnable in the tank?  This is fuel that is in the bottom of the tank below the intake tubing end.  Now throw in how level the vehicle is, as that will also affect it.   So, bottom line, you can’t be 100% sure how much fuel left in your tank is burnable.

Well, I don’t know how the unburnable fuel issue could be eliminated.  But, I do believe this would be far less an issue if you had an accurate proportional level readout.  This would go a long way to determine non-fuel starvation risk fuel stops.

Perhaps the only solution would be to have a fuel gauge that could be user calibrated on a linear scale that could be set to best indicate the true level value.  There just seems to be a need for a far more accurate way to determine how much fuel there is in your vehicles tank.

So, keep your tank full and enjoy.

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