Ok, I've read many of these threads about MPG, and I see that several people are getting the 18-20 that the car sticker is rated. And some of those people aren't even "babying" it (ie. shifting at 5-7k, having some fun).
It might sound like a stupid question, but, why am I getting less than 13 mpg?

I have an 04' model with 60k miles (just hit it yesterday), upgraded ignition, changed oil not too long ago, I neutral roll into nearly every stop, shift between 3-4, and i don't idle long before i take off in the mornings. I put premium gas in my car last week. Its traveled 130 miles and i have a quarter tank left. This has been the case for the last month or so. I'm at the point, where I don't watch my speedometer, I watch my fuel gauge. =[

I'm tired of reading people say, "just get rid of it," or "you don't buy it for the gas mileage." I love the car, and I didn't buy it for the mileage, otherwise, I would have bought a Cr-z or some other hybrid. However, I'm just baffled at the mileage. Is there anything that I can do to improve this?

 

Adapted list from the previous page:

Gas mileage will drop if any of these are not top notch. How much it drops depends on how many of these are not working at their peak and how far off peak they are. Many just a bit off could be just as bad as 1 severe failure.

- coils
- plug wires
- plugs
- engine compression
- Front O2 sensor
- Rear O2 sensor
- clogged cat
- clogged air filter
- engine block grounds
- fuel trims
- vacuum leak
- MAF fouling
- ESS fouling
- brake pads dragging
- tire pressures far too low
- engine coolant temps at cruise
- Driving style


What haven't you checked yet?

 

I took the car to the dealership about 3 weeks ago, where I got a full check-up from bumper to bumper, and the only thing that came back was the power steering rack, which I then replaced the following weekend. I don't know if the dealer checks for all that, but I paid $100 for a full check up, and they said it was running perfect (minus the steering).

 

In that list, the only thing the dealer would have actually checked is the tire pressures, brake pads, and maybe the air filter.

That kind of "inspection" does not get deep enough to actually cover the rest. Largely, dealers rely on the computers within the cars to tell them if something is wrong with how the car is running. The problem with that is that there are TONS of things that can go wrong and the ECU isn't equipped to identify all of them. Not even a majority of them.

 

How do you think I should go about and check for the rest of them?

 

If you're putting it into neutral chances are you are missing any (minimal) benefit of throttle overrun. It'll actually burn less fuel if you let it throttle down with your foot off the gas and down shifting to a stop.

The only time I've ever gotten 18+ mpg is on the highway. If you're in stop and go city traffic 13 mpg isn't that far-fetched... although I tend to get closer to 15.

You should always be putting premium in. Anything lower than 91 and you may hear a knock.

Please don't just fire her up in the morning and drive. You need to let the 8 warm up to operating temperature before putting any kind of meaningful load on the engine.

 

Thanks, I'll start down shifting to stops more.
And in the mornings, I usually give it roughly a minute, which is around the time that the rpm drops from around 3k to 1k. Then I drive it light, barely touching the throttle until the engine warms up. But even after it's warmed up, I still drive it pretty light.

Thank you guys for the advice, I'll work on my driving style more, and I think I'll devote this weekend to checking out the list RIWWP put up.

 

Hey guys I have an interesting mpg numbers...in town I averaged 15.7 mpg short trips but I did 300 miles on the highway and avg 15.9 going around 70 mph. Any one else had this happen?

 

Well it also depends on what gear/rpms you were driving in. If your doing 70 in 3rd gear don't be surprised to get crappy gas mileage. I get shitty MPG in general since all I do is stop and go city driving and I redline the hell out of my car any chance I get.

 

I guess you didn't read a few posts back? If you can't get at least 20mpg with 100% highway then there is something wrong.

The list of possibilities was posted 6 posts before yours:

 

Fixed it for you!

 

Whoops! Thanks. Fixed the original as well.

 

Thanks RIWWP for that list already looking into the DIY. Still learning the car and this one loves being driven hard ; I did almost 18 mpg driving on the highway yesterday driving her in fun spurts.

 

Update: I just calculated today (miles driven/gallons of gas)....18 mpg right on the dot.
Seems like it's starting to break in. Now, to replace the air filter (it's at 15k miles).

 

Just finished an 800 mile drive and ended up averaging almost 23 miles/gal. 70-90mph interstate driving.

 

Just wondering....... Why is everyone worried about gas mileage??. The rx8 is not a daily driver car. It's a fun car that has the drive ability like no other. If you need gas mileage buy a Honda. The rx8 wasn't made for mileage. This was the big mistake Mazda made with the rx8 was to satisfy the emissions etc , the rx8 was miss labeled as a daily driver( Not saying you can't drive daily). It really isn't a stop and go sit in traffic type of car, besides how can any one expect gas mileage at 7,000 plus rpm's, in other words how the car is designed to drive (Hard)?.
Just wondering why any one is discussing gas mileage?.

 

Because even though generally low, and the car isn't purchased for efficiency, a car's gas mileage is a pretty good indicator of how healthy it is. For example, a completely healthy RX-8 should be able to get 22mpg highway easy. Less than that and there is something wrong that could be improved. 14mpg highway or less, and there are either many things wrong, or one or two that are quite severe. All of these problems would also mean a loss of engine power, which IS of interest to us.

So yes, whining about 20mpg is worthless, discussing why your mileage is under where it should be certainly has value.

 

++ RIWWP.

I teach my kids to watch mileage, they tell me when it drops, then it is time to look for a problem..

 

They HAD to meet emissions testing to be able to sell them (depending on that countries rules)

 

Oh no! I've been doing it all wrong....
71,000 miles, 23 mpg average.

 

There is no wrong or right, other wise we would all agree on what oil to use. Milage iis as pointed out a barometer of sorts to gauge thing on, however there are many more so I don't get preoccupied or wine as it was put about fuel economy as long as fuel economy stays in a general area. Of course if I all of a sudden start getting 10 mile per gallon, I am not going to blessfully keep driving but I suppose by that mileage I would notice some thing else wrong ....maybe. he he.

 

@SLIDIN8: Enter the politic!. Enter the confusion. Enter the disagreement, tempest in a tea pot.

 

The R8 is a performance based car so milage is secondary, if you are worried about milage get a tiny 4 cyl. With my 06 Shinka I average 16 to 18 mpg, I upshift at 6000 to 10000 rpm and also match revs downshifting (Surprisingly when I don't match revs my milage will go up 3 to 4 mpg for a total of 19 to 21 mpg.) Just my two cents worth.

 

Ah men.

 

Gilbert, you shift at 10k ? You dont have a the OEM engine in your car ?