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Mildmay Automotive

Driving Smart


Every culture has its ideological blind spots.  In time, these ideas become so profoundly rooted in its psyche that they’re rarely debated and are eventually accepted as factual.  Such is the case with a number of questionable and even humorous gas saving myths.  So we decided to compile a list of the 10 most commonly held misconceptions: 

Myth #1 – Newer Gas Stations Have More Accurate Pumps

Since every state has a Weights and Means department responsible for regulating the proper measurement (fuel volume), vapor recovery and quality of motor vehicle fuels, the age of the pump does not make a difference. Field officers regularly examine fuel dispensers. Once the dispenser passes the inspection and meets all legal requirements, officers place a dated seal on the dispenser.  If the dispenser does not pass the test, the department will take enforcement actions to ensure the dispenser is repaired and recalibrated before it can be put back into service.

Myth #2 – Gas is Denser in the Morning 

The time of day has absolutely no effect on the volume of gas a pump dispenses.   Density is defined as the ratio of mass to volume and while it’s true the density of a liquid will increase when temperatures drop below 40 degrees F, the gasoline being pumped out of the ground is dispensed at a uniform (ground) temperature which is independent of the ambient air temperature.  Also, gas pumps measure volumes of gas, not densities of fuel concentration.  In other words, you are charged according to "volume of measurement" not the density of the liquid.

Myth #3 – Using the Air Conditioner Will Worsen Fuel Economy

Remember hearing your father say, "Turn the A/C off! It wastes gas!"  While the A/C compressor does pull power from the engine thus using more gas, the effect appears to be fairly minimal in modern cars.  Furthermore, putting the windows down, especially at elevated speeds, tends to increase drag thereby canceling out any measurable gain from turning the A/C off.  According to an Edmunds.Com test, driving with open windows produced roughly the same miles per gallon as using the A/C.

Myth #4 – Avoid Filling Up When a Tanker is On Site

There’s no arguing that when a tanker fills a station's underground tanks, it’ll stir up any deposits at the bottom of the tank.  However, the gas station’s filters should remove any sediment well before it reaches the nozzle so it will not clog your car’s gas filter.  Also and as described in Myth #1, the Department of Weights and Means not only inspects the pumps, but it periodically takes fuel quality samples for chemical analysis to ensure that the station meets state and national legal requirements.

Myth #5 – Only Buy Brand Name Gas

It’s important to note even before addressing this myth that simply stated, octane is a measurement of how hard it is to ignite the gas and has nothing to do with the quality of the gas.  With that said, one prevailing Internet theory holds that “top tier gasoline stations” provide a higher quality gas which will yield better economy.  The fact is that most brands of gas come from the same refinery for a given region – only the company’s specific additives are different.  So check with GasBuddy.Com and buy from the least expensive source which is usually found at an independent station. 

Myth #6 – Parking in the Shade Will Stop Gas from Evaporating

We don’t know where this one originated, but it’s totally bunk too.  Modern cars have closed loop systems so gas from a regularly used vehicle will not evaporate from the tank thus XX poorer gas mileage. 

Myth #7 – Using a Higher Octane Will Improve Fuel Economy

When deciding on what grade of gasoline to use, we recommend first reading the owner's manual to determine if a particular grade of gasoline is "required" or if it’s "recommended."  If it is recommended, a lower grade of gas could be used if you’re willing to accept a slight reduction in performance.  Most modern cars have a sophisticated engine management system which is the equivalent of having a laptop under the hood your car.  The EMS controls the knock sensors and will protect the engine from pre-detonation that can cause internal damage.   Therefore, we recommend using the lowest octane gas that won't make your engine knock. 

Myth #8 – Keep Wheels Aligned for Better Mileage

It is important to regularly inspect suspension and chassis parts for damage and misalignment.  In addition to just being unsafe, bent wheels, axles, bad shocks, broken springs, etc. will increase fuel consumption by creating a drag on the engine.  But while a misaligned car will ruin a perfectly good set of tires, it has minimal affect on fuel economy. 

Myth #9 – Additives Don’t Work 

For the most part, this is a true statement.  However, bogus gas additives that promise phenomenal performance and improved gas mileage – often referred to as “snake oils” – should not be confused with legitimate products like Chevron’s Techron or BG’s 44K which are designed to clean the entire fuel system.   Normal wear and tear, high temperatures and poor quality gasoline can contribute to a buildup of olefin wax, dirt, and carbon on the fuel injectors, all of which inhibit performance.  Using a proven fuel injection cleaner at least once a year will remove these deposits and help improve the efficiency of your engine. 

Myth #10 – A Clean Car Will Provide Better Gas Mileage 

While the remains of a thousand bugs plastered across the front of your car isn’t very attractive, it really won’t adversely affect the aerodynamics or the fuel economy.  As an aside, by regularly cleaning your car, hopefully you will notice things like underinflated tires, dirty or clogged air filters, or other gas-robbing issues which will ultimately affect fuel economy.