but but... the fan uses gas right?

Actually, if the O2 sensor is malfunctioning, the fuel consumption greatly increases because there's no sensor to confirm how much fuel your engine is trying to get from the tank.
An O2 sensor is the secondary to your A/F sensor

:haha: thx, you are the master :)

hold it right there, uninformed ricArs!!! j/k ;)

Having the heat on WILL affect gas mileage if you don't know when to use it/not use it. If you turn on the heat BEFORE your car reaches operating temperature, it will draw heat away from the engine, therefore prolonging the warm-up process. Since the warm-up process is what's responsible for most of the gas mileage drop you see, if you have the heat on TOO SOON it will, in fact have a negative effect on your gas mileage.

No, the heater motor does not use any gas, it's a freaking electric motor...damn.

Actually, the fan motor uses gas, indirectly. Where do you think the electricity comes from...

Ok, but the fan motor does not use significantly any more fuel than if it were idling. The alternator belt is still spinning and charging. Its not like you're powering some high powered amps or subs, its a small fan.

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im on the same boat as pwp type-s. my 97 EL (176,000km) only gets about 400km per tank, in the winter only about 320km, on straight highway driving then over 500km. ive done all the suggested and regular maintenance and nothing has changed. my transmission was rebuilt last year and timing belt was changed too. other than my mileage issue my car runs great.

im starting to think the culprit may be a faulty sensor. which sensors should be checked or replaced? will a faulty O2 sensor always throw a code? how can an O2 sensor be tested? what are the best brand of sensors to buy, i heard that NGK is best for honda/acuras.

wow my modified type-s gave me 450 last full tank.. and thats will moderate aggressive driving

dead babies?

are you not going to use the fans if you don't use the heat? :rolleyes:

surprised no one mentioned tire pressure...
potential flat with low air pressure would cause loss of gas mileage.

Some of the really old old cars from the dinosaur era uses gas for the heater. Today's modern car uses an electric fan.

Sorry. Someone beat you to it.

Not absolutely true. I can turn on the heater fan with the motor off. I don't think that will use any extra gas.

It still does, indirectly, as it will reduce the charge on the battery, which later needs to be replenished by the alternator when the engine is running.

First Law of Thermodynamics, conservation of energy: energy can be neither created nor destroyed - it just changes forms. Anything electrical you run in the car will eventually require more gas be burned to generate that electricity, whether it's pulled directly from the alternator or from temporary storage in the battery.

That said, the energy required to run the heater fan (actually, usually a blower) will cause so negligible an impact on your fuel economy that it's not even worth mentioning. We could calculate it all out, but I wouldn't expect it to affect your mileage by more than about 0.1%.

Factor in the lights (which are on more often due to shorter day), defrost (front turns on the a/c compressor, rear draws a lot of electricity), heated seats, wipers, etc. it adds up.

^True that! Anything with electric heat - rear window, mirrors, seats, etc. - draw a pretty substantial amount of current. Check your fuse block, the rear window defrost probably uses a 15A fuse... heated seats the same.

can anyone answer these questions...

On older OBD1 cars, no. OBD2 (post 1995 cars IIRC) do.
If the car has over 80K km's and it is the original O2 sensor, then that might be it. I believe you can test the output voltage on the O2 sensor to see if it is still good, but I have never done this. Another way to test is to go to air care and see if the emmissions are normal or out of range.
For the O2 sensors, I usually go back to OEM. The OEM and aftermarket O2 sensors are NOT a wideband O2 sensor, so they are not that accurate when compared to the wideband O2 sensors that are used for tuning purposes.

My uncle has a mazda truck with a coolant temp sensor that reads cold even after driving for an hour. That could def affect your mpg.

^Is he sure it's not the thermostat being stuck open? Takes forever for a vehicle to warm up, especially in the really cold weather.

Up north, once it got below -10 or -15, we'd put a big piece of cardboard in front of the radiator, too, to help keep things warm... even with a winter thermostat it would take forever to warm up and KEEP warm with that super-cold air flowing through the rad.

so does my horn and I'm pretty sure it's not an electricity hog...fuse amperage is not really a good indicator :p

Try putting a 5A fuse in for your rear defroster wires and see how that works out :IDL

you don't press your rear defrost on and immediately turn it off either, Using the horn as a comparison is not a good example :p

logic pwnz you. I didn't say the rear defroster doesn't use much electricity now, did I? I simply said that just because something has a 15A amp it doesn't necessarily mean it uses a lot of electricity. You follow?

It's a perfect example to illustrate my point that you can't say that something uses a lot of electricity because of the fuse's amperage.