Performance Hypermiling with Mazda Miata's

5X Racing 1999 Mazda Miata Fuel Efficiency Research and Development Project

We not only use the Mazda Miata for fun at the track here at 5XR, we also use them everyday for our daily commutes. We have two 1999 Mazda Miata's within the 5XR family here, and both cars accumulate at least 300+ miles in a week as they take us back and forth during our daily commutes and errand running. When so many miles are driven every week, fuel mileage and efficiency are always a concern. Not only is the Miata a blast to drive, it is also does fairly well with fuel efficiency. But "how efficient" was the question we wanted to know. So, here's what we did to find out how efficient the Miata really is and how we went about our study, read on and we hope you find this informational!

Our Plan:

Well, we love Miata's (obviously), and two of us here drive them on the street everyday (John and Rick). We knew they were better on fuel than the Mustang GT's that we both drove before we got into Miatas, but the question was "How good?". Our plan is simple: to find out what is the best MPG that one could acheive in a stock Miata, and what modifications would help you (or hurt your mpg's) acheive better fuel efficiency?

The Research:

To research how good a Miata is on fuel is easy, one must drive a Miata A LOT and be willing to perform various modifications to the car in an effort to experiment! Well, we do that here! The primary test subject is a 1999 Mazda Miata driven by John, and is driven 350+ miles a week in not so consistent conditions. Rick's Miata is driven 500+ miles a week in ultra consistent conditions (we both have LONG commutes!). John's Miata is driven in 70% stop and go traffic with many starts and stops, while Ricks Miata is driven in 90% highway with hardly any stops, so we cover the whole range of the spectrum with our research. We used Ricks Miata as a reference point for a completely stock Miata and did not track the numbers on it, but have a rough estimate of fuel efficiency using the traditional "total miles on tank divided by gallons needed to fill up" method of fuel mileage calculations and have discovered some interesting things about the Miata with these two driving conditions, and have discovered some surprising facts about the Miata that might surprise you in the meantime. Please read on to find out what we've learned!

How we recorded our fuel mileage and the tools we use:

Figuring out your fuel mileage is as easy as topping off your fuel tank, resetting the trip odometer to 0, then the next time you fill up your car, you top off the fuel tank again and divide the total miles of your trip odometer by the amount of fuel used to fill up. Or something like this: 350 miles on tank/10 gallons of fuel used to fill up = 35 mpg average fuel mileage for that tank

OR, you can go a little higher tech like us and use some pretty neat tools. The first thing we use is a ScanGauge II Vehicle Monitor. In short, this awesome tool is basically a car computer that will display your realtime fuel mileage, your average fuel mileage, and a vast amount of information about your car as it is running. We use the ScanGauge II to show us our real-time mpg, our average mpg, our intake air temp, and our water temp. The ScanGauge II will also tell you how many miles you've driven, how many gallons of fuel you've consumed, how many gallons of fuel you have left, how many miles you have left to your tank, etc... In other words, it tells you EVERYTHING about your car! Whatever information your ECU is gathering, the ScanGauge will display it to you, and keep track of your fuel mileage in the meantime. It's a must have for any fuel miser or hypermiler!

The other little high tech gadget that we use is the Pocket Garage App for the iPhone. Pocket Garage is a great tool for keeping track of your fuel mileage as well, but it also can help you keep track of your service and maintenance performed/due on the car as well. We use it to log all of our fuel fillup's and log our modifications and maintenance work performed. It is perfect for us because it eliminates having to keep a handwritten log of your fuel mileage tracking, and we can keep track of our findings by creating nice reports such as these: Click here to view our Pocket Garage Fuel Mileage log from January 2012 - April 2012

Our Numbers:

  • John's 1999 Miata sport averaged 31.24 miles per gallon through 23 tanks of fuel
    • all tanks driven with the timing set at 14 degrees
    • all tanks driven with 93 octane, 10% E10 ethanol fuel (common pump gas)
    • all tanks driven with our experimental full length intake with high flow air filter
    • all tanks driven with a lightweight flywheel installed
    • all but a few of the tanks were driven with the top up, only once did we drive the majority of the tank with the top down
    • we used the air conditioning very little, and never throughout the course of a whole tank (you can see the differences in the numbers on the Pocket Garage Log between the tanks that where A/C was used and when the top was down, they are in the high 29's for average fuel mileage)
    • the majority of the tanks were driven below the 60mph threshold (see below)

Facts and Discoveries:

There are many things we've learned so far and are not nearly done with our long term tests. The easist way to explain our facts and discoveries is to list them and describe the reasons "why" we've figured these things out:

  1. Fact: The Miata does MUCH better than the EPA's rated 22mpg city/27mpg hwy/24mpg combined. (more below)
  2. Discovery: The Miata acheives better fuel economy in stop and go traffic then it does in highway conditions.
  3. Fact: Driving with the top down results in a loss of about 5mpg over the course of a tank of fuel
  4. Fact: Driving with the air conditioning on all the time results in a loss of 3-4mpg over the course of a tank of fuel
  5. Discovery: 60mph is the breakover speed at which the Miata becomes inefficient. Driving over 60mph continuously will net averages of 28-30mpg. Driving under 60mph will net averages of 30-33mpg. 
  6. Discovery: Advancing the ignition timing of a 1999 Miata will NOT decrease your fuel mileage, and in fact advancing it to 14 degrees BTDC will actually help your fuel mileage

Primary Test Subject:

John's 1999 Mazda Miata Sport Edition

Specs and Modifications: