The other, less obvious impact is the change from "winter" gas to "summer" gas...especially if they have a higher percentage of ethanol = lower mileage. Here in S. CA I can almost always tell exactly when they change to summer gas as my mileage take a hit (and conversely with swap back to winter gas).

 

Summer gas should have less ethanol, not more. I always get the best fuel mileage on good old fashioned gasoline. They started oxygenating fuel a long time ago with MTBE, but stopped using that because it seeps through the tanks at the gas station, and pollutes the ground. In more recent years, they oxygenate gasoline by adding ethanol. They say they do it, because it reduces emissions that come out the tail pipe.

I have never understood the logic behind that, because I am burning more gallons per trip. How can it be better for the environment to burn more fuel, and get less miles per gallon?

Up to a couple years ago, they would not use this oxygenated fuel in the summer time, because the ambient temperature was too high, and the unburned fuel in your tank would put out VOC's (in laymen terms, that's just another form of pollution that is caused by evaporation)

Here in Oregon, I was under the impression that it became a law that all gasoline sold at the pump contain 10% ethanol year round. This is due to economic reasons, claiming that this keeps gas prices down -however I think this is one factor that may be driving up our grocery bills too!

Myself, I need to do some research to find out if it really is a law here, if there are any exceptions, or if it was just a temporary thing last year. Real gasoline is more efficient than the winter stuff, and I'd rather do my part for the environment by being more efficient (and having more power LOL) -than to be less efficient with fuel consumption whilst artificially inflating the price of corn as a commodity. (Ok, I'll stop ranting now)

AlexQS

 

I thought I should post a retraction, as after some research I discovered that I was not 100% correct.


I had thought that this requirement was a law, because a couple years ago I received a recall notice from Subaru, and took my Impreza to the dealer to get a free computer re-flash which optimized the fuel map to run more efficiently on E10 fuel, which as the dealer correctly told meat the time had become a law in Oregon.

I had believed that this was because of the economy, but in Oregon, it was because we failed an air-quality test. Now (in 2013), since we have passed that air quality test in Oregon for at least 2 consecutive years, we can legally run ethanol free premium fuel (-at least in the summer time, not sure about winter yet). It is hard to find information about it, and seems like its being kept quiet, and I know most gas stations around here are still selling E10 blends.

I found a gas station close to me, and I telephoned them. They have zero-ethanol 92 Octane Premium gasoline at the pump (though their website only advertises that they sell E85, Biodiesel, and other alternative fuels.). You can legally put this zero ethanol gas in your car in Oregon, whereas not long ago you could only legally burn it in an airplane, a boat, or farm equipment.

The current info on EPA website is lacking, and other information on many .gov websites seems to be outdated.

This link was helpful to me, and I found the info I needed for my state by simply telephoning the gas station.

http://pure-gas.org/ Click on this link, then find your state.

I hope this may be helpful for those who are seeking zero-ethanol premium gasoline.


(and sorry about the misinformation in my previous post)

AlexQS

 

Mine has done the same thing, was easy to get 30-31 on the highway before 30kmiles on the car (cruise, 72MPH), now (88k) it's more like 28 (ish), sometimes lower.

Heard also from Detroit Tuned that the R53's tend to carbon up the valves, which gradually eats at mileage and performance. I had good luck with a treatment of Seafoam - follow the instructions - but others (Way) swear not to use it. (YMMV, your risk if you use it). I've noticed smoother performance, but have not had the chance to just do a long highway run except travel to the Dragon, which was slightly faster and towing the Brave little Trailer (essentially an 800-900 lb parachute).

"Wider tires have more rolling resistance and also less aero, plus a little weight. All bad for FE." = VERY true. Changing to 215/45/17 ate at my indicated gas mileage, but then I realized I was now running a 2% larger tire, which means 2% "reduction" just through the mathematics, let alone any rolling resistance/aero changes. I think the factory runflats were also better for mileage, as the sidewalls were stiffer.

Also, I had a chance to talk with the "Assembled Mini Knowledge of the Western Hemisphere" since Helix, Detroit Tuned, Way, and Group4's Lenny were all at MOTD last week. All agreed that some R53's are mileage monsters, and others struggle to break 30 on the highway, where the newer R56 engines (S and justa) are more consistent mileage-wise.

 

Around town I see 25-26mpg. On the highway 31-33 if I keep it under 70mph. I am running 215/45/17 Conti DWS on very light Enkei RPF1 rims. Going to a light rim will definitely help with fuel mileage.
Also everyone keeps mentioning tires and rolling resistance. Make sure your tires are properly inflated as this will help also.

 

A failing O2 sensor seems to describe my problem exactly. Is changing this a big project or what? Is there a thread on here about it?

 

Changing O2 sensor is not difficult.

Front O2 can be done from the hood, or underneath (way easier from underneath). Open-end wrench is the way to go, no need for (and barely room for) O2 sensor socket. They're spendy, though,. about $175 each, and I believe both are the same part number.

Remove old, CAREFULLY insert new, tighten to manufacturer's instructions. The plug unplugs from the wiring harness, then a 45 degree twist removes the clip itself from the engine mount. Replace clip on new O2 sensor, 45 degree twist, replug, re-run wires into clips, and you're good to go.

They're installed with anti-seize and mine came out no issues after 87kmiles. The new ones have pre-applied anti seize on the threads, do NOT get it on the sensor.

 

Could you define "properly" when it comes to tire inflation? I have Sumitomo 215/45/17s rated at a max psi of 51 so I usually keep the psi around 45 because that's just what I've always known. Am I way off?

 

but yes, 45 psi is fine, just dont want to run say 20 psi, that will make a noticable difference

 

The door jamb has pressures that mini reccomends. 45 is high. I run 35 ( pilot super sports )

 

I find 35-38 on the street is fine....track folks often adjust in 1 psi increments to tween handling....at 45 the car must ride like a wagon on wooden rims!! Sounds like it is a bit on the high side...look at your tires and check how the centers are wearing.

 

One other thing that sometimes pops up is having a dealer or someone else overfill the crankcase. Over filling it seems to make the mileage go down on mine (like when I get lazy and just pour the whole last quart in rather than adding a little and checking it -- not that I've ever done that, mind you).