So I bought this 04 RX-8 2 months ago, thought it'd be fine with the car running on a full tank everytime for 160 miles, but as i read on, other people seems like getting much more than 13 mpg, so can anyone tell me what could be wrong with my car?
Sparks plugs? tires? uh... idk... What could be wrong??

And please for those people who are just trying to tell me what gas milage they are getting, you are not helping...

O, and btw, sometimes it takes about 2-3 seconds to start
just a thought it might help u guys figuring it out...
Thanks

 

I get 25 city and 33 highway.

 

Coils. Spark plugs. Spark Plug Wires.

24mpg city/highway mixed.

Period.

.

 

I just Seafoam my car.
And I got 210 miles before the empty tank light is on with 50/50 city & highway drive.

I didn't have 200 miles per tank for a while already.

 

meh i get 150 to the last quarter, with new engine, new coils, new plugs, and a rebuilt transmission thats making a new weird noise

i also can get to 200, driving style makes a massive diffrence, sad this new engine seems to get worse hwy mpg then my last one.

clogged cat?

 

d00d, guiz, I once went 600 miles with only a quarter tank. TOP THAT!

 

Coasting ftw?

 

clean the maf sensor

 

I just drove two nights ago on a full tank of gas and got 345 miles to the tank. Personally, I don't think that is all that great for windows up, straight highway driving at 75 mph and the air conditioning off half my drive. I think that is what, 23.8 miles to the gallon?

 

bah, after i installed HKS racing suction and legamax exhaust, 1 full tank is now 250 miles, don't know why, and don't care! lol

 

I go along with Shazy's recommendation to check the ignition stuff. 2-3 seconds of cranking is excessive. With the original ECU, these cars start almost instantly. After the 4206f flash, they'll start after a couple of revolutions.

What kind of driving do you do? Highway? City? Meek? Spirited? 13 sucks, but it's not outside of the range that people talk about here.

Ken

 

i usually fill up whenever i reach 1/4 tank left and i do 100% city driving with a LOT of spirited driving every day i drive and get about 160 miles to 3/4 of a tank.

the 2nd day i had the car i drove to dallas, tx and back and averaged 85 miles to each 1/4 tank i used

 

Honestly, what I've been observing lately.. especially since I've been tracking my gas mileage...

Tune up (normal plugs, coils, etc) will help a pretty good amount, depending on how bad it was in the first place
Assuming your engine is running fine, It's really just driving style

I can also easily hit 160 miles on a tank, if I constantly drive at school where it's pretty much stop and go. You're not going to get much better without hitting the highway.

I honestly think.. after nearly 70k miles, that about 22 mpg+ is only reserved for the highway.

BUT surprisingly, I found that (at least in MY 8) when i speed, I get BETTER gas mileage vs. 65. Honestly, I can hit 75+ miles per quarter tank when cruising at a higher speed while I will only get 55-60 going a lower speed.

Not endorsing speeding, but it's something to think about.

 

Ignition system...Coils ,Leads, Plugs.

Tires..make sure you have enough air in them, can make a 5-10% difference.

MAF Sensor Clean.
Blocked or dirty air filter element?

Have you tried Pre-mixing, IMO you get better compressions because of better sealing between your metal seals, etc. (apex, side and corner seals).

Fuel grade or quality...use premium, I get better mileage when I do.

Engine oil, yep, this can also have a slight effect on MPG, how long ago was the oil and filter changed?

 

Pre-mixing ftw

 

i got an ignition upgrade, changed the plugs about 10-12k miles ago (same time as the ignition upgrade), highflow cat and i still can only get 160-180miles on a tank of gas, car seems to run fine i dont notice anything strange, i def wish i could get an extra 30miles to a tank or so

 

What's your tire width? That makes a big difference too.

I get 16-17 mpg with a Cobb tuned motor, AEM CAI, Greddy Evo TT exhaust, and 245/40/18 F 275/35/18 R. Plugs and coils have about 8k miles on them.

 

my first two tanks after buying the car were 170 miles per tank. Now, using 87 octane I see 240-250. Using 92/93 it's about 215-220.