9krpmrx8

iTrader: (46)

Like I said, I have done the trip to my parents house 170+ miles away a few times where i have hit no traffic late at night and had the cruise at 70-75 the whole time and I got 20MPG once and close to that a couple of times.

I never add 5-10 bucks of gad here and there, I always wait until the light is on and fill up with at least 13-14 gallons. The only time I do not is when we do our canyons runs and then I just fill up half way through the trip because gas stations are scarce.

justgr8t

my little experiment is over and I think the culprit has been short trips/ratio of cold starts to miles driven. I have two types of trips since I work from home, very short pick up the daughters from dance or school trips where the engine just reaches operating temp or lets go play on some back roads where I'm shifting at 6 to 8k rpm.

I drove 141.7 miles on 6.97 gallons of gass all highway or 20.3 MPG. I kept the cruise control on 71 MPH which = 3600 RPM in 6th. It was painfull, especially when the elderly lady in a minivan with go grdma vanity plate passed me but with the help of god and cruise control, I managed not to step on the gas. So just in case some future unfortunate is looking at 12 or 13 would recommend they go all highway and see what they get. NOt that 20 highway is bragging rights but beats the heck out of 12.

DocBeech

iTrader: (1)

You should be getting better fuel mileage in the cold. You get more oxygen in the engine with the denser air.

Also keep in mind they use different blends of fuel for winter and for summer. So hopefully you are getting a winter blend.

We should also note if we are running E10, E15, and Ethanol free fuel. There is a huge difference. I drove from Houston to Dallas on Ethanol free 93 octane fuel and got 22.5MPG, but on E10 93 octane I was only able to get 20.5 so keep that in mind.

York

Yeah as far as I know all the gas stations I use here (I've been exclusive to Shell V-Power) is E10.

DocBeech

iTrader: (1)

I went through all of your fuel logs and I did notice something. The guys getting higher fuel mileage are running 93 ocatane highway miles. I also noticed that some of us, like mine reads 20mpg is the annual average, but 9K reads 21 is the average (per EPA). So I will email them about it and see why. We both have GT 04 models.

neXib

My best (real) mileage is in the 24-25 range, and that's both long highway trips and spirited mountain driving. I drive a lot of shorter stop and go trips, try to avoid them or make them longer, but that's what I do anyway. So all things considered the mileage is pretty good. If anyone had my car and commuted without standing in a queue all day I think they'd have a damn good mileage tbh. (considering the rumour of the car). I use 95 octane (RON)

paulmasoner

iTrader: (1)

nice to see another who can be one of the few of us to attain mileage that good. I'd say 25 was my highway average, though as mentioned elsewhere I have done 26-27. It was nice while it lasted, but the speed where I drive(live) now is more fun

PeteInLongBeach

So, what are you suggesting? Are we lying, massaging the numbers, or just too stupid to calculate fuel mileage properly? I've been collecting and restoring cars for almost 40 years, and I work in IT. I know how to do a simple fuel consumption calculation.

Did you think to consider that the owners you have encountered at various meets are mostly a demographic of enthusiasts who might drive their cars more aggressively than I do? Or, perhaps that demographic of enthusiasts mostly drive the lower geared manual transmission models, which generally use more fuel on the highway than the higher geared automatics. Oh, and by the way, I appear to be averaging the EPA highway rating for the A/T model, so there's that.

What do you want? Notarized fuel receipts, maps of where each tank was driven, trip computer showing speed data, a hired professional to ride along and swear to it all? What?

I only watch fuel consumption as one tool to help confirm whether the car is running normally. For instance, lately it has dropped to between 22 & 23 mpg, instead of its previous 24. This might be attributable to colder weather, oxygenated winter fuel, etc. But at 25,000 miles, and considering the idle is not quite as smooth as new, I'm assuming it's time for plugs, MAF, and air filter service.

paulmasoner

iTrader: (1)

i understand his disbelief, its simply because there are apparently very very few of us that get mid 20s. I've only ever seen 4 or 5 people besides myself state 25+

Flashwing

I averaged 26mph once and only because the altitude of the car caused the tune to lean out to 15's and 16's. Cruising speeds were ok but I had problems when climbing some hills. This was on a road trip through New Mexico.

Other than that, 19mpg on average and it's fallen to about 14mpg with the turbo. Blah!

neXib

I have a 38mpg fill up but I also have a 9 and 0 before and after, so it makes sense "averaged" I believe. Dunno why it turned up like that though, may have been when I changed some things in the program. Everything else is exact, entered at the pump. My engine has 34000 km on it if it matters.

REDRX3RX8

Doc, You're thinking out of the box here, but IMO you'll get better mileage during mild dry weather like fall or spring (less air going in per compression means less fuel to even the ratio).

The winter blends have more butane for better vaporization, and the ethanol blends are taxes on us serfs for tribute to the kings.

My best average for a whole tank (27.1 @ average 75mph) was achieved with 91 oct (no alky here) in October with some A/C and a 20mph wind mostly behind me from Midland to Weatherford.

I can drive out of San Antonio (93 oct with alky) going home at about 75mph, and get 24mpg only, so I think you're right about the 2 mpg loss with alky.

DocBeech

iTrader: (1)

I have been doing research on the effect of ethanol for years now. Mostly to the disbelief of the majority. I believe it causes poor fuel mileage, and I started looking into it on my drives to and from the ranch in Llano Texas. We have a 2500HD farm truck that we drive back and forth. On the trip down to Llano its filled with Dallas fuel. On the trip back its filled with ethanol free 89octane fuel from the ranch. Now the trip from Llano to Dallas is down hill. The airport there is 1040 ft and Dallas is about 440ft. I only know this because sometimes we choose to fly the Cessna. So its a down hill trip back of only 700 feet. But my fuel mileage increases by 3.5 mpg. This has been tested over the course of 250,000 miles put on the truck. 700 feet over the course of 220 miles.

220 miles is 1,161,600 in terms of feet. So that means I am traveling 1 foot down for every 1700 feet forward. Or about 3 feet a mile. Thats not enough to make a significant difference.

Secondly I think its the cause of the poor performance of our water pumps.

Ethanol is a well known and common cause of airplane engine failure. We had to learn all about it when I was getting my pilots license. Its extremely harmful to engines despite what the EPA says it destroys engines.

SpeeD_TeaSe

I live in canada and I never really knew what my mpg was i was getting maybe 300km in a tank so i finally calculated it and divided by 1.6 then divided by 12 for the gallons wich gives me about 15mpg, i always let it warm up before i go and now for winter it takes awhile to warm up in -30C which sucks up a lot of gas, minus mostly city driving and the redline because 'A redline a day keeps the mechanic away' but i am getting around 11-13mpg for winter and im not redlining it like crazy only one time in a ride and shift it at maybe 3-4rpm

Tiler02

I just started recording my milage but the best I have had was 20 with all hiway miles, I also have a heavy foot

Old Rotor

If you let it sit there warming up you lose mpg. If you have a good tune on the stock engine, start it up and give it thirty seconds. The idle will have started going down and it's safe to drive away easy. No revving and keep your foot out of it till it gets to normal temp. You will be fine.....relax.

Grace_Excel

iTrader: (5)

I agree, I moved to a new job closer to home where I only take four miles on the street, my mileage have decreased from 18 to at least 14 mpg. I normally start the car, let it idle for 30 seconds to a minute then take it for a drive. I'll shift before 2500 rpm until the engine's at normal operating temperature.

HiFlite999

iTrader: (2)

Did it:

http://www.fuelly.com/driver/hiflite999/rx8

Now how to I get the cute summary box to appear??

In plain English, 29 fillups, 21.7 mpg (seeking more)

DocBeech

iTrader: (1)

click on the vehicle, then look at the bottom of the left side. You will see the tiny badge and a link that says Fuelly Badge. You have to be inside the vehicles profile.

justgr8t

Doc, you think I should be getting better mileage? What would you suggest as next steps. I checked into three local dealers. New plugs 270 to $320, air filter $70 to 120 quoted. Hook up to see if any codes are being thrown, advice I got was that check engine light would be on if any codes were activated?

Seems like I'd be taking some pot shots at making mileage better without really knowing what the problem is. Everyone sounds knowlegeable, do I just start plugging things in to see if mileage gets better. Still getting around 14 when not highway driving, and yes I've been taking it easy on the rpms, rarely over 4k (still redlining once per day though).

At the end of the day do I just accept the mileage is what it is or, if not, what would you look at first?

DocBeech

iTrader: (1)

14 is on the lower end, but I average lower than that on the track. Coils plugs and wires you can get much cheaper at o rielys. Visually inspect your air filter, if you don't see any discoloration you should be ok.

You can start off by cleaning the throttle body and idle port. Including the SSV. After that try seafoaming the engine. Don't idle the car for more than 30 seconds. Thats where we loose a lot of fuel. Just start it up, wait for the needle to drop to say 1500 and go.

If all else fails we would need to know the miles, and other information to suggest a compression check or not.

Grace_Excel

iTrader: (5)

I just installed my set of new ignition coils from O'Reilly's for $35 each. Ordered and shipped the next day. I think the idle-for-30-seconds approach it good to cut down on use of fuel; however, it doesn't mean that you could redline the engine immediately. I try to shift below 3000 RPM until the temp's at an appropriate level.

DocBeech

iTrader: (1)

It takes a lot of self control on my part to redline before temps read at least 180 lol

DocBeech

iTrader: (1)

Reviving an old thread here after a successful experiment. I broke my own habits of redline driving to do this so I sacrificed for you:P I was able to get 25.9mpg. No thats not a mistake (I record MPG by odometer). I drove 271 Miles this last fill up and filled up on 10.4970 gallons of fuel. It really comes out to 25.88 but fuelly rounded up. How I did it.

I drove using the vacuum gauge as my only guide. Ethanol Free Fuel. No traffic 96% highway. The rough estimate but I only drove about 24 miles city (highway to my home is 3 miles). Using only the vacuum gauge I ignore my speed. 70mph was my zero. When I went up hill I completely ignored the speed decline and when I went down hill (limiting to 10mph) I let the car do its thing. Two of the keys to note, Ethanol Free Fuel/Vacuum Gauge Driving. Redlined only once per 1/4 tank. Now I never made it below the last 1/4 was just about right at. My fuel light comes on at a little over 13 gallons even though we have a 16 gallon tank. So Gauge wise I drove three full redlines (Redline through 3 gears) 3 times. Redlined only at safe temps. All other shifting was done between 2-3K. No launches, no hard acceleration. All acceleration was limited as much as possible to slightly over cruise vacuum levels.

I will do this experiment again with city blend (E10) fuel in the future. But I think the fuel had a ton to do with it. I was expecting to hit 22 or so, and was just shocked when it read almost 26.

mdm9421

I get a little over 20 mixed and about 26.8 on the highway. I was getting about 16-18 and I took my car in for it's first oil change and then the mileage jumped is this normal?