The other day, a friend of mine told me he was saving money on gasoline.  He said he noticed that where he lives,  93 octane premium gas, cost him $4.30 a gallon, but 87 octane regular gas cost only $3.99.  The way he figured it, he was saving 31 cents a gallon.  “Premium gas, just isn’t worth the extra price”, he said.  Well, I wouldn’t disagree that gasoline has become pretty expensive these days and saving every cent possible makes sense.  But I couldn’t stop thinking whether my friend was correct.  So, I grabbed a pen and a calculator and decided to test his theory.

I simply used the calculator to divide the premium grade gas price that he switched from, by the regular grade gas price, that he switched to.  In my friend’s case, the calculator said he was paying about 8% less per gallon.  This information alone did not help me.  I had to find out how many miles per gallon my friend was getting on both grades of gasoline.  So, I gave him a call.  He said he knew he got about 30MPG on premium grade gas and regular grade seemed to be a little bit less, but not so much.  He needed to test it.  A week later, he called me to let me know his gas mileage was about 26 MPG and felt vindicated in his choice of a lower grade of gas.  I was less certain and out came my trusty calculator and pen.

I did some more division.  Dividing the 30 MPG using premium gas by the 26 MPG using regular gas, I estimated his miles per gallon had declined by about 15%.  Now, I had all the information I needed to let my friend know he was actually spending more money on gasoline, not less, by switching to a lower grade.  He didn’t believe me, so I had to prove it to him.

I showed him that the relative difference in price for both grades of gas, about 8% was less than the relative difference in mileage, about 15%.  But I wanted to make the difference more tangible.  So, I asked him, “Approximately, how many miles do you drive in a year?”  He said, “Around 15,000 miles.”  I said, “Great!  Let me show you how much of a difference this is going to make to you.”

“If you drive 15,000 miles a year, getting 30 miles per gallon, you’ll buy 500 gallons of gas.  But if you get 26 miles a gallon, you’ll need to buy 577 gallons of gas to drive the same 15,000 miles.  At today’s prices, you’ll be paying an additional $307 for the extra 77 gallons of gas you’ll need to buy.”  My friend was blown away and thanked me for the advice.

Before you switch grades of gas, here are a few things to consider:

  • First, consult your owner’s manual.  Some vehicles cannot use certain grades of gas because they are harmful to your engine.
  • Next, keep track of how many miles you get per gallon at each fill up.  If you switch grades of gas, this will make the comparison of prices and mileage quick and easy.
  • Don’t drive to the next county because there’s a gas station whose prices are a nickel cheaper than the gas station down the road.  Often, the small difference in price isn’t worth the trip.
  • Get a pen, paper and a calculator and see whether the lower grade is more economical or not

Here’s how:

Is changing grades of gasoline worth it?