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Old 05-29-2011, 10:45 AM
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MPG problem

I bought my 8 for almost 1 month, and everytime when I fuel up it full, I check the miles for each 13 gallons, still 190 miles =.=', even after I change oil. That's really bad because I calculate it only 14.6 mpg =.='. I know I'm new with stick shift and it's a big waste of gas, but that too low MPG. The light on the upper of ABS light is on, and I don't know What I should do with it.
Old 05-29-2011, 11:10 AM
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are you driving with ur ebrake on?
Old 05-29-2011, 11:18 AM
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definitely no sir, I use e-brake only when go to the hill ( only 1 time with this 8).
Old 05-29-2011, 11:32 AM
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Don't forget to do the "first $100" and post $100. Cleaning MAF, replacing spark plugs, replacing coils, replacing cables. See where you are after those things are done. You should see an improvement. Just from cleaning the MAF alone my MPG jumped up about 2mpg.
Old 05-29-2011, 04:07 PM
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Originally Posted by Lancifer
Don't forget to do the "first $100" and post $100. Cleaning MAF, replacing spark plugs, replacing coils, replacing cables. See where you are after those things are done. You should see an improvement. Just from cleaning the MAF alone my MPG jumped up about 2mpg.
Just to make it a bit clearer for him, if he changes the spark plugs and coils he will be looking at a little less than $300, not sure on the wires. Definitely search for that "first $100" thing though, there are free or next to free mods you can do in that same thread that can help the car.


OP what are your driving habits? Do you keep the rpms low or are you redlining it everywhere you go? If you have a heavy foot then 13-14 mpg in the city wont be uncommon for you to get.
Old 05-29-2011, 05:40 PM
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I always shift gear at 4,5k or 5k rpm. The Coil is new, clean, but I've not changed and check the spark plug yet. But for 100$, I think it's not enough for a set of spark plug =.=', anyway I will change it soon!
Old 05-29-2011, 05:48 PM
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sounds pretty normal for city driving
Old 05-29-2011, 06:05 PM
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I get 15mpg in the city. I shift at the same rpms too. Seems normal...
Old 05-29-2011, 06:15 PM
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yep, very normal for me as well... I get around 270km to a tank in the city thats based on 51 litres of gas
Old 05-29-2011, 06:29 PM
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When I got my 8 a few months ago I was getting around 13mpg city and 17-18 highway and had a slightly rough idle. I cleaned my MAF which immediately fixed the idle and over several tanks my mileage crept up to around 15-16 city and 20-21 highway.
Old 05-29-2011, 09:30 PM
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How many miles do you have on the car, is this 04 with 77k miles your trying to currently sell? I think you should pop out at least one of the front rotors spark plugs and see how it looks. Post a picture in this topic if you are not sure about it. Just when you thread it back in make sure you screw it in by hand and then tighten with a ratchet.
Old 05-29-2011, 09:36 PM
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Originally Posted by rotary's dream
I always shift gear at 4,5k or 5k rpm. The Coil is new, clean, but I've not changed and check the spark plug yet. But for 100$, I think it's not enough for a set of spark plug =.=', anyway I will change it soon!
The spark plugs n such are post first 100.

The first 100 consists mostly of free things to do like cleaning your MAF which will improve things for you.

Here is the link dude:

https://www.rx8club.com/new-member-forum-197/congratulations-you-got-8-a-202548/

It works.
Old 05-29-2011, 11:50 PM
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Mazda should improve the rotary engine, starting from the miles per gallon of the car. When driving the rx8, it's like driving a gas guzzler like those big and heavy suv's and trucks.
Old 05-30-2011, 12:13 AM
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@Monchie: I like your reply :D.
@Xexok: Yes it is , I will try to clean the spark plug tomorrow when I have no car on front ground, and will check everything soon.


@All: If 15mpg is normal for an 8, I think I have nothing to do after clean up everything like the "first 100$" thread :D. Thanks everyone.
Old 05-30-2011, 02:00 AM
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The first $100 thread really has some great ideas. If you want to check at least 2 spark plugs very easily just jack up the drivers side of the car and turn the wheel all the way right, remove the little cover that blocks you from seeing the engine from the wheel well and you will be able to see your front rotors spark plugs. A good size extension(24"+) is a VERY nice thing to have here, just remove the plug and check it. Should not take you very long to do at all. Just be careful when tightening them since the plug is steel and the block is aluminum bad things can happen if you go he-man on it.


As far as mpg though, on a trip to colorado(700+ miles) all highway I got around 22 mpg, which is pretty good I think. My old car was a 2.5L v6 and I usually got around 30ish mpg all highway, so not a huge drop and I have much more fun in the rx8. In the city only you will probably be right at 14-17 mpg depending on how you drive it. I pretty much drive it like I stole it so my mpg is beyond horrible. I don't even check to see what I get because it would probably ruin my day.
Old 05-30-2011, 10:29 AM
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^^This
Old 05-31-2011, 05:52 AM
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Fuel consumption yesterday: PS to LA

Don't hate
I know... hard for me to believe too - see attached pictures of scangauge trip display, and dash tripmeter vs fuel guage.
And, it's time for new spark plugs - daily commuting average is down from 24 mpg to 23 mpg...
Attached Thumbnails MPG problem-rx8_28mpg_trip_3.jpg   MPG problem-rx8_28mpg_2.jpg  

Last edited by PeteInLongBeach; 05-31-2011 at 06:04 AM.
Old 05-31-2011, 07:47 AM
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Oh hells no.. I am all about hatin' on you with that MPG. LOL. Is it all highway? Mine is stop and go for an hour+ highway and residential and I burn up a tank a week. Sitting idle sucks. Gotta find a better route to work.
Old 05-31-2011, 07:27 PM
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Originally Posted by Lancifer
Oh hells no.. I am all about hatin' on you with that MPG. LOL. Is it all highway? Mine is stop and go for an hour+ highway and residential and I burn up a tank a week. Sitting idle sucks. Gotta find a better route to work.
2 tanks for a week, just drive to work and back home about 18 miles away, 15 miles on freeway and 3 miles local, but cost me 3 gallon each day .
Old 05-31-2011, 07:56 PM
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thats just about what i get.
Old 05-31-2011, 09:31 PM
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Originally Posted by rotary's dream
2 tanks for a week, just drive to work and back home about 18 miles away, 15 miles on freeway and 3 miles local, but cost me 3 gallon each day .
You only drive that much and its 3 gallons a day? You really should check you plugs, coils, maf, etc. Maybe even check your air filter and see if its super dirty, 12 mpg mostly highway is pretty bad or even 15 mpg if your "18 miles" or 3 gallons is off a bit.
Old 05-31-2011, 09:42 PM
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My commute is 7 miles, 14 miles total. It's the sitting idle and the stop n go that kills my mileage. When I "clear the pipes" during weekends by going long highway distances it gets better. But once I am in that stop n go it drops right back down. I am sure if I was not sitting idle it'd be much better. Yes 1hour+ to go 7 miles. Mostly because people in MA have no idea how to merge so traffic comes to a halt at merge zones.
Old 05-31-2011, 11:23 PM
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Originally Posted by Lancifer
Is it all highway?
Sorry, I should have been clearer. It was Palm Springs to Los Angeles, about 110 miles / 1 hr 50 min, on freeways, 2009 automatic.
Old 05-31-2011, 11:27 PM
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Originally Posted by rotary's dream
2 tanks for a week, just drive to work and back home about 18 miles away, 15 miles on freeway and 3 miles local, but cost me 3 gallon each day .
With that freeway-to-local driving ratio, you should be getting better fuel consumption. Try all the maintenance items previously mentioned here and you should do better.
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