Overview and Goals:
When the time came to replace Brittany's daily driver 2000 Mustang GT, as Mazda racers we were naturally drawn to the Mazda RX-8 for it's looks, handling, usefulness, and super cool rotary engine. While we knew the rotary powered RX-8 did not get Mazda 3 gas mileage, we were still surprised to find out that the rotary got around the same miles out of a tank as a the V-8 Mustang GT it replaced. This is quite acceptable being a sportscar, as you sacrifice fuel mileage for power, ride quality for superior handling, creature comforts for weight savings, etc... In other words, we knew what we were getting into when we bought the car.
After the first tank of gas came and went, and the next, and the next, with about 275 miles squeezed out each tank (20.5 mpg), it left me thinking that there had to be some way to get better gas mileage and at the same time not sacrificing power, but GAIN power. There are several ways to save mpg's, but some will reduce performance, such as reducing gear ratios and unspirited driving. We want to preserve the spirit of the Mazda RX-8, and at the same time see if we can increase power output while getting better gas mileage.
What we will be doing with Project MPG is performing simple modifications at every oil change for one year and logging the gas mileage to see if what we did had any effect on mpg's. The modifications will be simple at first, such as: using different engine oils, installing a Green High performance air filter, using different spark plugs, upgrading the spark plug wires, replacing the transmission and rear end oil with lighter weight equivalents, etc...
Follow along with our project and hopefully it will help you get better gas mileage out of your RX-8, or any car for that matter. I hate to think that many RX-8's get traded in shortly after being purchased because people expect the car to get 30 mpg, perhaps because it is "Japanese", "has a 1.3L engine", or is a "lightweight sportscar" and forget the fact that it has a rotary engine that consumes more fuel than a piston engine. We will be adding information to this page continuously, so check back ofter for updates and planned modifications.
Modification: The strict useage of Castrol GTX 5w20 non-synthetic oil
Modification: Addition of a ScanGauge II 3-in-1 Automotive Computer (special thanks to project sponsor Linear Logics) added to monitor fuel efficiency during the project duration
Modification: Addition of a Green High Performance Air Filter
Modification: Installed Magnecor KV-85 Racing Spark Plug Wires and NGK Laser Iridium Spark Plugs
Modification: The use of ethanol free gasoline for several tanks in comparison to normal E10 fuel
Our goal was to monitor and evaluate the fuel mileage performance of our RX-8 and determine if there was anything that could help us acheive better fuel mileage. After a year of monitoring and logging fuel mileage, and adding certain subtle modifications, we concluded that the rotary engine is just not meant to be as efficient as a small piston engine. The engine is meant to be a fun, high revving, small liter powerplant meant strictly for purists. The racecar drivers, tuners, corner carvers, and enthusiasts are who this car is made for, not the soccer moms, gas misers, or "a to b" type driver. Although it is a shame it doesn't get better fuel mileage, it doesn't matter because the car is just that much fun! Hope you found this educational, and I hope it didn't sway you from purchasing an RX-8. The car will average out to around 20-21 mpg, which is better than any truck out there and about the same as a Mustang GT. Not too bad when you look at it in that light!
Linear Logics: Manufacturer of the ScanGauge II 3-in-1 Automotive Computer