Premium vs. Regular


When gas prices rise the cost difference between premium and regular gas becomes much more noticeable.   Being the frugal Scotsman that I am, I couldn’t help but wonder at what point does it make more sense to buy a car that gets lower miles per gallon, but uses regular gas, as opposed to the higher miles per gallon that some cars get with premium?

The good news is not all that many cars require premium, it is merely recommended.  If your owners manual recommends premium, according to experts such as “Click and Clack” (the Car Talk guys – Tom and Ray Magliozzi), you should be okay using regular, unleaded gas much of the time.  According to Click and Clack most manufacturers that recommend premium do so because they are using a high compression engine.  These engines provide increased power out of a same-size engine.  These engines run best with higher octane gas which prevents engine “knocking” or “pinging”.  The knocking/pinging sound is created when the fuel ignites too early.  To prevent the knocking manufacturers (since about 1996) build into the car an knock-sensor that retards the spark.  This causes the fuel to ignite at the correct time and thereby eliminates the knock or ping in most instances.

Click and Clack warn to be sure and check the owners manual but if it says that premium gas is recommended, not required, you can safely use regular gas.  If the engine does start to knock, you can always switch back to premium with no harm done.  The change from premium to regular shouldn’t have any affect on your gas mileage but could have a minor impact on engine performance.  For the record, if your car’s engine is designed for regular gas, putting premium gas in it will not improve performance or gas mileage.

Now, if you are considering the purchase of a car that requires premium (such as the Mini Cooper or Countryman) then the question is, is the advantage of higher gas mileage wasted because it require the more expensive premium fuel?  For example, the Cooper averages about 32mpg, the 2012 Volkswagen Golf uses regular but only averages about 26 mpg.  So, from a cost of fuel standpoint, which car is the better purchase?

Lets say you drive your Golf 12,000 miles per year and gas is 3.75 for regular.  In this case your annual cost is approximately $1,730 for the Golf.   If premium is selling for $4.02 and your Mini Cooper averages 32mpg its annual cost is 1,507; a $223 dollar difference.  The fact is, better miles per gallon can be fairly quickly offset by higher fuel cost.  If the Golf were to average 29 miles per gallon instead of 26 you would save money with the Golf; not much money, about 44 dollars per year.  Of course, if the price difference between regular and premuim fuel increases you will need to get better mileage from your Cooper to make up the difference.

So, based on my rough analysis, if you are deciding between a car that uses regular gas and one that requires premium, all things being equal, buy the car that uses regular gas.  Of course, all things are never equal so buy the car that makes sense for you and is the most fun to drive.  Life is to short to worry about a few pennies per gallon.  Happy motoring.

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