neit_jnf

iTrader: (17)

Taken from the rx8club:

INTRODUCTION

Well, as promised, here are my data on 20 tanks during my long distance drive from Los Angeles to Atlanta to Jacksonville, FL, to Houston to Austin and back. Sorry for the delay, but I've had a lot of things to take care of since I've gotten back home. I don't know if anyone else has done a trip of this size, but if not, I believe this may be important FIRST-TIME information for all RX8 owners and would-be owners.

Every tank is with DSC off and TCS off (some people have surmised that mpg may be better with both off). Unfortunately, I did not test with DSC and TCS on, so those comparisons can not be made. Every tank was on the highest octane offered at that gas station in that region of the country. CRUISE CONTROL WAS USED continuously unless otherwise noted (e.g., in city driving in Atlanta or Austin or wherever). A/C was off unless otherwise noted. At the start of the trip, my odometer was at about 12,000 miles. My car had run one full tank with the "L" flash before the trip began. I had not made a comparable trip without "L" flash, so those comparisons can not be made, unfortunately. Every tank included 1 to 3 quick pit-stops either for bathroom (I apologize for my passenger) or rest area (sleep for me). 60, 65, 70, and 75 mph were tested. Please have your atlases ready, guys!

*** Edit ***

My car is a 6-speed manual and was built in September, 2003.

*** End Edit ***



FIRST LEG: LOS ANGELES, CA, TO ATLANTA, GA (interstate 10 to interstate 20, which becomes the 20/59 from Meridian, MS, to Birmingham, AL)

** Note: the date is when I filled up the tank and the mileage is what followed on THAT tank. **

1. Sun 3/21: 368.2 mi/13.878 gal = 26.531 MPG @ 65 mph
91 octane, Shell, Los Angeles to Phoenix, AZ, mostly 82-102 degrees Fahrenheit, 70 degrees at the end
very slightly uphill, I believe

2. Sun 3/21: 323.5 mi/14.567 gal = 22.208 MPG @ 75 mph
91 octane, Union 76, Phoenix to Deming, NM, mostly 50-60 degrees
very slightly uphill, I believe

3. Mon 3/22: 320.4 mi/13.867 gal = 23.105 MPG @ 70 mph
91 octane, Chevron, Deming to Pecos, TX, 55-65 degrees
very slightly uphill, I believe

4. Mon 3/22: 305.3 mi/13.185 gal = 23.155 MPG @ 70 mph
91 octane, Chevron, Pecos to Eastland, TX, 65-70 degrees
very slightly uphill, I believe

5. Mon 3/22: 334.6 mi/14.421 gal = 23.202 MPG @ 70 mph
93 octane, Chevron, Eastland to Shreveport, LA, 45-55 degrees
very slightly uphill, I believe

6. Tue 3/23: 312.2 mi/13.855 gal = 22.533 MPG @ 70 mph
93 octane, Texaco, Shreveport to Meridian, MS, 35-45-55 degrees
got off hwy at Jackson, MS, to look for food/bathroom and did some hard accelerations

7. Tue 3/23: 337.3 mi/13.542 gal = 24.908 MPG @ 65 mph
93 octane, Shell, Meridian to Atlanta, GA, 65 degrees
quite a bit uphill, at Meridian the interstate 20 becomes the 20/59, which goes northeast up to Birmingham, last 37 miles were city driving

Comments: none at this time



FIRST LEG: ON THE ROAD WITHIN ATLANTA

8. Tue 3/23: 286.1 mi/14.725 gal = 19.430 MPG @ various speeds
93 octane, Chevron, Atlanta, GA, 70-75 degrees
city driving and fwy driving, no cruise control, LOTS of hard accelerating

Comments: saw a titanium and a silver RX8, waved to both, and got waved back by both; the most beautiful city in America; couldn't help pushing my car to the limits in Atlanta, which is unsurprising if you have ever experienced Atlanta roads, which are incredibly narrow and winding and are perfectly suited for the RX8



SECOND LEG: ATLANTA TO JACKSONVILLE, FL (interstate 75 to the highway 23)

9. Thur 3/25: 56.1 mi/2.022 gal = 27.745 MPG @ 60 mph
93 octane, Shell, Atlanta to McDonough, GA, 75 degrees
slightly downhill on the interstate 75, no stops, got caught in bumper-to-bumper traffic in the last 10 miles and got off hwy in McDonough, GA, to refill tank and gauge mpg gotten because I knew it would be my highest ever

10. Thur 3/25: 330.9 mi/13.501 gal = 24.510 MPG @ 60 mph
93 octane, McDonough to Jacksonville, FL, 55-65 degrees
the hwy 23 is a winding country road and oftentimes going slightly uphill, had to break out of cruise control often and slow and speed up again

Comments: The leg from Atlanta to Jacksonville is around 350 miles, which is short enough such that differences in mph mean very little difference in arrival time, which gave me the perfect opportunity to test 60 mph and try to get maximum mpg. However, I met with two unfortunate circumstances. First, unbelievably, I got in a traffic jam on the interstate 75 going south out of Atlanta (tank 9). I don't know how much mileage was drained from 10 miles of traffic jam but at least I chose to get off the hwy at McDonough, GA, to refill and calculate my highest mileage to date: 27.745 mpg. Second, instead of taking interstate 75 down to interstate 10, I made the extremely unfortunate decision to take hwy 23 at Macon, GA, which looked like a much more direct route from the atlas but wound up zapping my mileage (tank 10). But this tank from McDonough to Macon, according to my car's gas gauge, would have topped the 27.745 mpg. And it would have been a significant difference, too. What a shame. I should have taken the 75 all the way down.



SECOND LEG: ON THE ROAD WITHIN JACKSONVILLE

11. Fri 3/26: 50.8 mi/2.529 gal = 20.087 MPG @ various speeds
93 octane, Shell, Jacksonville, FL, 60-70 degrees
city driving, no cruise control

Comments: nothing to do except watch Dawn of the Dead; 28 Days was better



THIRD LEG: JACKSONVILLE TO HOUSTON, TX (interstate 10)

12. Fri 3/26: 349.3 mi/13.729 gal = 25.442 MPG @ 60 mph
93 octane, Shell, Jacksonville to Pensacola, FL, 55 degrees
slightly uphill

13. Sat 3/27: 321.7 mi/12.384 gal = 25.977 MPG @ 65 mph
93 octane, Shell, Pensacola to Baton Rouge, LA, 70-80 degrees
slightly uphill, last 25 miles were city driving in Baton Rouge

14. Sat 3/27: 300.2 mi/13.565 gal = 22.130 MPG @ 75 mph
93 octane, Shell, Baton Rouge to Houston, TX, 75-85 degrees
last 20 miles were city driving in Houston

Comments: Again, my efforts to get maximum mileage @ 60 mph are thwarted by a less-than-ideal fwy that gradually inclines (tank 12).



FOURTH LEG: HOUSTON TO AUSTIN, TX (hwy 290)

15. Mon 3/29: 168.8 mi/7.284 gal = 23.174 MPG @ 75 mph
93 octane, Shell, Houston to Austin, TX, 65-75 degrees

Comments: beautiful, straight country road with farms



FOURTH LEG: ON THE ROAD WITHIN AUSTIN

16, Mon 3.29: 157.5 mi/8.764 gal = 17.971 MPG @ various speeds
93 octane, Chevron, Austin, TX, 75-85 degrees
city driving, no cruise control, lots of accelerating

Comments: an unusually high percentage of Mazda cars of all kinds on the road. Can anyone explalin this? Aranda's has the best REAL Mexican food I have EVER had at super low prices.



FIFTH LEG: AUSTIN TO LOS ANGELES (hwy 290 to interstate 10)

17. Tue 3/30: 278.3 mi/12.132 gal = 22.939 MPG @ 70 mph
93 octane, Chevron, Austin to Sheffield, TX, 45-55 degrees
quite a bit of gradual uphill, put in 1 quart of Castrol 5W20 before leaving Austin

18. Wed 3/31: 309.4 mi/13.677 gal = 22.622 MPG @ 75 mph
92 octane, Phillips 66, Sheffield to El Paso, TX, 55-65 degrees

19. Wed 3/31: 347.2 mi/14.253 gal = 24.360 MPG @ 75 mph
91 octane, Shell, El Paso to Tucson, AZ, 70-75 degrees
gradual downhill, A/C on all the way, traffic accident caused bumper-to-bumper condition just outside Tucson

20. Wed 3/31: 366.7 mi/14.409 gal = 25.449 MPG @ 70 mph
91 octane, Tucson to Cathedral City, CA
gradual downhill, A/C on for the first 60 miles

Comments: I had gotten used to gauging reference points on my car's gas gauge but it seemed the tank (tank 17) coming out of Austin threw everything off. The only change I can think of is that I added a quart of oil just before leaving Austin. Surprisingly, A/C appears to have little or no effect on mileage (tanks 19, 20). Any comments on these two issues?



CONCLUSIONS

1. 75 mph: hwy cruise: 22.1 to 24.4 MPG (avg 22.9; 5 samples: tanks 2, 14, 15, 18, 19)

2. 70 mph: hwy cruise: 22.9 to 25.4 MPG (avg 23.4; 6 samples: tanks 3, 4, 5, 6, 17, 20)

3. 65 mph: hwy cruise: 24.9 to 26.5 MPG (avg 25.8; 3 samples: tanks 1, 7, 13)

4. 60 mph: hwy cruise: 24.5 to 27.7 MPG (avg 25.2; 3 samples: tanks 9, 10, 12; however, all three tanks were from highly compromised portions of the trip)

5. The lowest realistic speed for hwy driving is 65 mph, although most people drive 70 to 75 mph. Driving 70 mph instead of 65 appears to cost 2 mpg, whereas driving 75 mph instead of 70 costs 1 mpg. People who prefer to drive under 70 mph should feel good about the gains in MPG. People who prefer to drive around 70 mph should feel good that they lose only about 1 MPG when pushing it up to 75 mph.

6. It is clear to me that, if not for the compromised conditions in my 3 samples at 60 mph (tanks 9, 10, 12), my car would have gotten significantly above 27.7 MPG. This may lend support to others in the forum who have claimed 29 to 31 MPG.

7. Air conditioning (A/C) appears to have little or no effect on MPG (tanks 19, 20).

8. Adding oil may affect the rate at which the gas gauge falls, which makes no sense to me (tank 17).

*** Edit ***

9. It should be noted that, before this trip, in Los Angeles commuting mostly on the fwy, I had been averaging right around 21 MPG, with a handful of lows in the 18's and several high 22's and one in the low 23's. Hence, the mileages from this TRUE long-distance trip on CRUISE CONTROL is HIGHLY IDEALIZED and are different from fwy driving in one's city area.

*** End Edit ***

peejay

Big woop. My FB gets mileage like that as long as I stay out of 5th gear.

tjgosurf

I'm glad to see you werent using exxon. thats almost as good as just hooking the hose up to your cars tank.

WaveMagnet

Great stats, neit_jnf! My 08/03 build RX-8 GS6speed, just turned 75k & I have mpg stats for all but a few tanks, but no time to analyze the results. I run 110-130 mile daily commutes at 80-85mph, when allowed, and seem to be averaging ~19.5. One or two blasts to 9K+ on each tank. Mostly 87octane. I'm sure if I dropped down to 70-75 mph speeds my mpg would shoot up, but the only way to keep steady speeds in LA is to stay in the #1 lane where "do nothing to place in jeopardy the safe and customary flow of traffic" is THE only rule, which means 75-85. Getting ready to install an RB airbox and ram intake, so hope that will help on mpg at hi-way speeds. One of these days I'll get around to posting the full lifetime results here and on www.rx8club.com (I'm "MPG > HP" over there). I log octane, weather, flash version, and general driving conditions, so the results should be pretty telling, as my commutes are fairly routine. - Gary, Newport Beach, SoCali

jic

iTrader: (1)

nice!

WaveMagnet

Forgot to add, my previous RX-7s (84GSL/SE, 86GSX, 87SC), all got ~22 mpg on similar routes that I'm running the 8 on, so quite a downer on the mpg scale. But then the increase in NA HP is significant, so no complaints, especially as this car is so much more refined than the SA or FCs. Aside from perfect design balance and great handling, the most noticeable difference in the 8 is seen on long road trips. After 6-8 hour the older version seats get to be a pain, but the RX-8 makes you want to keep zooming and zooming and z....! No experience with the FD, so would like to hear a comparo from someone who's owned both FD and RX-8.