How do you calculate the MPG for your car? Follow these instructions and use the calculator below.
1. First, fill up your gas tank to full.
2. Reset your trip meter (next to your odometer) on your dashboard to 0.
3. Travel 100 miles or more (the more miles the better). Try to isolate driving between traveling on highways/freeways only and street/intersection conditions.
4. Then refill your gas tank to full and enter your values below and click on calculate.
I have heard that reducing your speed helps conserve fuel. But how much of this is really true? To run a simple test, I looked at the RPM meter while driving 80mph and 40mph. At 80mph, it appears I'm consuming enough fuel to spin the engine at 3500 revolutions per minute. Theoretically if I were truly saving gas, I would think my RPM should be less than 1750 RPM while travelling at 40mph.
My actual RPM results at 40 mph? about 1750.
Evidently, slowing down didn't seem to reduce my RPM relatively but instead only reduces the time it takes to get to my destination.
An argument maybe that wind resistance slows you down at higher speeds. If that were true, wouldn't my traveling speed then be reduced to 75 mph if I were to maintain 3500 rpm? I suppose that would be true if I had a box-like car. Fortunately, most Honda Civics have aerodynamic characteristics.
Maybe putting this to the real test will show different results. While driving consistently between 70 - 80 mph along a 22.7 mile freeway, it appears I've consumed 0.55 gallons of gas which equates to 41.27mpg.
Next, I'll run the same road while driving around 60 mph to see just how many gallons I consume. After driving the same road for 22.7 miles while maintaining a 60 - 70 mph speed limit, it appears I had consumed 0.61 gallons of gas which equates to 37.21mpg.
So there you have it, no gain in miles per gallon if you drive slower.
Here are a few ideas that might make more sense.