new engine same bad mpg..??
05-13-2011 | 03:43 AM
#1
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new engine same bad mpg..??
I bought my 04' At.. 5 months ago.. Drove it for a week was at Mazda for 4+ months.. Finally have it back and all previous reving and grinding noises or gone due to new engine plugs wires and coils.. (car runs beautifully and has been flashed with 'N') but I'm on my 6th tank and I'm still getting 170-220miles to a tank. 10-13city 14-15mpg highway. Air filter is clean.. Doesn't matter driving hard or soft. It got the same mpg before it went in..It just sucks.. Please help... Thanks
05-13-2011 | 07:28 AM
#3
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From: Colorado
Was the CAT checked, as in looked at visually while the teardown was in process? Dealer often "won't" look at the CAT unless directed by MNAO techs, which is dumb and stupid, but true, even if there is a good chance it's bad. And is it an auto or manual. Tell us how you drive, that is, what gears you use mostly in city and highway. How do you calculate mileage? Not trying to be silly or demeaning, but there are big differences in what people do/how they drive their cars.
05-13-2011 | 07:50 AM
#5
Some stuff to check, and points about making a topic about it.
Gas Mileage:
If you are considering, or have purchased, an 8, you will likely have one of 3 opinions on gas mileage:
1) I am buying a sports car, or won't be driving this regularly, so I really don't care about mileage
2) I care a bit about mileage, but I think what I get is fairly reasonable
3) WTF, I am getting terrible mileage, these car's suck! All RX-8's are gas guzzlers.
If you have the first or second opinion, then congratulations and join the club. If you have the 3rd, then keep it to yourself, we aren't interested in listening to it. Gas mileage has been discussed, killed, resurrected, killed again, reincarnated, burned alive at the stake, beheaded, cremated, and BURIED AT SEA. Please leave it there.
The reality is, a healthy RX-8 will get 17-18mpg city, 22+mpg highway. But 'healthy' means completely healthy: healthy coils, wires, plugs, O2 sensors, carbon free engine, good compression, healthy cat (or no cat), good transmission/diff fluid. Let even one of these slide, and your mileage WILL drop, and it will drop fast. If you believe that RX-8s simply can not get this mileage because you have never seen it, then there is only 1 person to blame, and that is YOU. If you don't get this mileage, then there is something wrong with one of the above points. Or with your foot. Your right foot can make the mileage drop quite a bit as well. And I don't mean granny driving as the answer to good gas mileage. Smoothness is more important than speed. Smooth and fast is better mileage than unstable and slow.
People also tend to point at it being a 1.3L engine, and assume that a 240/238/232 hp rotary "2-stroke" engine is as efficient as a 1.3L 4-stroke piston engine (which is probably in the 70-90hp range). This simply is NOT the case.
So if you can't get this mileage, start poking around for what is wrong.
For reference, here is 8,330 miles of mileage data from my Sevenstock trip around the country in September 2010. The lowest tank was 13.99mpg (14mpg basically), and that was in non-stop tight curves on the Pacific Coast Highway where I was having fun blasting along. Note the 4 tanks over 23mpg, 11 tanks over 20.00mpg. Also note how the highway mileage drops as speeds go up. Once you cross the ~70mph range, the wind resistance does start stacking against you more and more. It's easily a several MPG drop going from a cruise of 70 to a cruise of 80+. And those were probably closer to 85-90. The 18mpg in northern NV wasn't really highway, but it was alot of really straight empty terrain, and speeds that I won't talk about publicly
If you are considering, or have purchased, an 8, you will likely have one of 3 opinions on gas mileage:
1) I am buying a sports car, or won't be driving this regularly, so I really don't care about mileage
2) I care a bit about mileage, but I think what I get is fairly reasonable
3) WTF, I am getting terrible mileage, these car's suck! All RX-8's are gas guzzlers.
If you have the first or second opinion, then congratulations and join the club. If you have the 3rd, then keep it to yourself, we aren't interested in listening to it. Gas mileage has been discussed, killed, resurrected, killed again, reincarnated, burned alive at the stake, beheaded, cremated, and BURIED AT SEA. Please leave it there.
The reality is, a healthy RX-8 will get 17-18mpg city, 22+mpg highway. But 'healthy' means completely healthy: healthy coils, wires, plugs, O2 sensors, carbon free engine, good compression, healthy cat (or no cat), good transmission/diff fluid. Let even one of these slide, and your mileage WILL drop, and it will drop fast. If you believe that RX-8s simply can not get this mileage because you have never seen it, then there is only 1 person to blame, and that is YOU. If you don't get this mileage, then there is something wrong with one of the above points. Or with your foot. Your right foot can make the mileage drop quite a bit as well. And I don't mean granny driving as the answer to good gas mileage. Smoothness is more important than speed. Smooth and fast is better mileage than unstable and slow.
People also tend to point at it being a 1.3L engine, and assume that a 240/238/232 hp rotary "2-stroke" engine is as efficient as a 1.3L 4-stroke piston engine (which is probably in the 70-90hp range). This simply is NOT the case.
So if you can't get this mileage, start poking around for what is wrong.
For reference, here is 8,330 miles of mileage data from my Sevenstock trip around the country in September 2010. The lowest tank was 13.99mpg (14mpg basically), and that was in non-stop tight curves on the Pacific Coast Highway where I was having fun blasting along. Note the 4 tanks over 23mpg, 11 tanks over 20.00mpg. Also note how the highway mileage drops as speeds go up. Once you cross the ~70mph range, the wind resistance does start stacking against you more and more. It's easily a several MPG drop going from a cruise of 70 to a cruise of 80+. And those were probably closer to 85-90. The 18mpg in northern NV wasn't really highway, but it was alot of really straight empty terrain, and speeds that I won't talk about publicly
05-14-2011 | 12:44 PM
#6
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Maf sensor was dirty thanks for the tip, cleaned it with Maf cleaner.. And still the same mpg... Cat was checked not to mention replaced in 07.. Plus no black smoke and the front and back of the cat are the same temp... Ohyea.. I Love my rx8 I drive a ship lot of miles that's why I would like get my daily driver to its full potential... 
.. Few things.. There is an annoying noise coming from the rear around 65-68 mph I swear its a wheel bearing but tech said its not.. And tires are in good cond. . So help with my conundrum please ,thanks..
.. Few things.. There is an annoying noise coming from the rear around 65-68 mph I swear its a wheel bearing but tech said its not.. And tires are in good cond. . So help with my conundrum please ,thanks..
05-16-2011 | 08:28 AM
#8
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It sounds like a wheel bearing in the rear.. Maybe differential.. a few tech guys believed it to be tire chatter and a few agreed with me and said it sounded like metal.. It is a droning sound from the rear which changes pitch upon differentiating speeds. . U joint? Differential?
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