According to the 2008 EPA ratings your 26MPG doesn't sound too bad. My mileage drops off in the winter here in northern Illinois also. It takes a lot of effort to get decent mileage in winter driving. Those that live a bit more south have it better than us. Be glad you don't live in Alaska where the four seasons areJune, July, August, and winter.

http://www.fueleconomy.gov/feg/calcu...1&id=20710

 

Watch for some gas pumps that say they pump more than they do. Happened to me - 1 pump give me 30 mpg while after gives me 43 mpg, which is about right for my HX.

So actually, some stations rip you off on gas with poorly calibrated pumps.

 

The top few sources I found on google suggest that warming up the car helps circulate oil throughout the engine, providing better lubrication. My sources:

http://www.stretcher.com/stories/970320e.cfm
http://www.popularmechanics.com/auto...o/4213313.html

On the discussion of expanding metals between EJ8 and 95civic--I was first inclined to agree with EJ8. On second thought, I realized (with my limited classes in physics, correct me if I'm wrong) that different metals have different thermal expansion rates. What does this mean? You can have 3 scenarios.

1. A steel piston inside a steel cylinder will maintain the same tolerance between the cylinder wall and the piston at any temperature. Assuming the temperature of the two parts are the same (which isn't going to happen when the car's running, but they'll be pretty similar), then the piston will expand as much as that hole (the cylinder) will. From what I know, cylinders and pistons are made of different materials because two same-metal parts moving against each other will tend to grip and sieze each other

2. An aluminum piston inside of a steel cylinder will have a decreased gap when the temperature rises. Aluminum has a coefficient of thermal expansion of 23, stainless steel 17.3, meaning that aluminum expands more (near 20 C) than steel does. The piston will be expanding at a rate faster than the "hole" in the steel will be expanding. I recall learning that a 1" circular hole in steel will get bigger at the same rate as a 1" circular disk of steel, so that's what I'm applying here.

3. The reverse of 2. A steel piston inside an aluminum cylinder will have an increased gap as the temperature rises, because the outside jacket is expanding faster than the piston is.



Sorry to jump off the thread topic, I didn't want to see this thread go in a different direction. In addition to what people have said earlier, you may also want to check how long it's been since your o2 sensor has been replaced. I would place an optimistic upper-limit on the sensor's life at 150k miles. Your o2 sensor can significantly affect your mileage as it tells your ECU when you're running to rich or lean. If you're running too lean, your ECU injects more fuel into the engine. One of the ways an o2 sensor can fail is to give leaner readings. That means your engine could be running optimally, but your o2 sensor says it's lean, so your ECU injects more fuel than is optimal. There's your lost fuel economy.

 

Oh boy... First off Jamned's research is supporting my arguments. The engine was designed to fit together based on the coefficients of thermal expansion. And your right the block expands at a different rate then the internal components, but another thing to note is that a Honda block is not pure aluminum, it's an alloy. Despite whatever its coefficient of thermal expansion is or how one metal compares to another, 95civic's argument is misleading and can lead other people to the wrong conclusion.

It is wrong to equate the meaning of compression with tollerance. Certain tollerances inside the engine are made to tighten up when they get warm and others are made to open up, this is all based off the coefficients of thermal expansion and it is the way the engine was engineered.

Perhaps were talking about the same thing, I just disagree with the verbage he used to describe it.

 

I only meant it uses fuel. It's up to you whether it's a waste or not. It certainly influences the MILES per gallon, which was the original question.

You still have to balance that against theliquid fuel wetting the cylinder walls for a longer time & providing more oil dilution.

If all the different materials had the same thermal expansion, then higher temperatures would INCREASE clearances. Since there's different metals, different values of CTE, you can't make that statement without knowing the details.

What's happening there is the skin temperatures are far higher than the internal structure temperatures. You don't get much of that in acarengine.

 

That was an example to explain the concept... I believe we are beating this thread into a pulp. Enough with the reiteration...

 

One other thing that hasn't been mentioned is weight. Are you carrying a lot of extra stuff in the car, like some subwoofers, heavy MDF boxes, heavy amps, or other audio equipment? Maybe a tool box? bike rack with a bike on it? bunch of junk? Aztec gold?

If the car has some extra weight, the engine has to work harder to get it up to speed, thus wasting more gas.

 

I've been getting 23-24 mpg in my 98 auto civic, I've heard something about companies watering down the gas

 

Yeah weight plays a factor too. I think by law gas companies have to post (somewhere at the gas station) what percentage of alcohol and what types of additives have been added to the gas. But yeah most companies do add alcohol to "water down" the gas, there might be a scientific reason they do this. If there is my guess would be to cut back on emissions considering alcohol burns a lot cleaner then petrol. In Los Angeles only a select few gas stations offer gas above 91 octane, which sucks if your running a high compression ratio or FI. I was wondering if this is because California sucks or if Los Angeles is too liberal (or both)? For people back east, what octane is available to you at a standard gas station?

This will date me a little but I remember when gas was leaded 100-110 octane.