reserve fuel tank in mazda 3

Well, if you fill it up whne the light comes on, how many liters does it take?

My expereinece has been at least 8 to 10 liters are left, except for a Ford LTD company vehicle. It would mark 1/4 tank left when it was dry.

Agreed, you are trying to measure fuel consumption in an odd way. This is how to do it.

1. Reset the trip odometer, (or write down the number on the main odo)
2. Fill the tank to the brim.
3. Drive around until the "low fuel" light is on.
4. Refil to the brim. Take note of the reading on the fuel pump, this gives the quantity of fuel consumed. (F)
5. Write down the trip odo reading, or subtract the recorded trip reading from the current one. this gives the distance traveled.
6. Divide one by the other, to give fuel consumption. (either MPG or L/K)

"Mal Osborne" wrote in news:448becd9$ snipped-for-privacy@quokka.wn.com.au:

Correct and if you want to know your real fuel consumption, do the above for an entire year. That will give measure of driving in all types of weather and conditions and will tend to average out the variations in how full you get the tank each time.

I can see doing it for a while to get an idea of gas mileage, or as a diagnotic to see if the car is using too much fuel, but if my friends & family saw me writing in a book and doing mpg calculations every time I filled up with gas for an entire year, I think, (and hope), that they would step in for my own good.

It's called obsessive compulsive disorder, and there are drugs to treat that. ;-)

Pat

You don't need to do the above every time. You only need to record the odometer reading twice: once at the start of the experiement and once at the end. Likewise, you only need to do on calculation:

mpg = (OdoEnd-OdoStart)*(total gas used)

I would think that calculating average mileage over 4-5 tankfuls ought to be sufficient to get an accurate number.

If it's not hurting anything, why worry?

I was just giving him a hard time, as usual. That's what the wink was about, the statement was purely tongue in cheek. :-)

Pat

Grant Edwards wrote in news: snipped-for-privacy@corp.supernews.com:

Yes, it will give you a fairly accurate number but that's not why you keep a check over the life of the car. You need a running check to tell you of impending trouble, sometimes a drop in fuel economy is the very first sign of needing new spark plugs, plug wires, clogged fuel passages, leaky injectors, etc. Even serious alignment problems will show up as a drop in economy before you'll see tire wear, some brake problems will also show up first as a change in economy.

You start the log to establish normal economy and continue as a maintainence tool, one of the very best there is for early detection of problems. It takes only a couple of minutes when you fill up to keep track.

There are way too many variables there for me. I would have to track highway versus city driving and how hard I was using my foot for that gas tank full versus the last one.

A heavy foot in town will result in a lot worse gas mileage, but even that could not be measured with any accuracy because it becomes a matter of how hard you hit that gas pedal and how often. Trying to keep up with something like that would be impossible unless you drive the same way all of the time.

I have gotten well over 300 miles out of a tank full. I have also gotten well under 200 miles. This was an indication of my driving habits far more than it was an indication of the condition of the car.

BTW, I am going to notice a serious alignment issue on a miata before gas mileage or tire wear becomes an issue. There isn't a problem that is much easier to notice on a miata than a bad alignment.

As far as plug wires, in over 7 years of reading posts on here, I have never seen even one diagnosis of bad spark plug wires based on fuel economy. It is always someone wondering why their engine has started hesitating at low rpm's, every single time.

New spark plugs? That is normal maintenance. Clogged fuel passages? That will result in a noticeable lack of power, no writing in a manual at fillups required. Leaky injectors? Gasoline has a very strong smell, my nose has always pointed me towards fuel leak problems anywhere on the car. If it is leaking enough to affect your gas mileage, the smell is going to be very strong.

Pat

pws wrote in news:%TEjg.24314$ snipped-for-privacy@tornado.texas.rr.com:

That's why you run a check over a long time. It works, I've done it for many years. I used to have an old VW that was a perfect example, over a period of time it would drop exactly one mpg, new plugs, set valves and timing and it went back up. There were no other symptoms, before a tuneup it ran like a total piece of crap and after a tuneup it ran like a total piece of crap but with better mileage.... :-(

Broad, consistent differences will be obvious, though. The replacement of pure gasoline with E10 resulted in a ~10% mileage decrease across the board. I noticed when both my best and worst cases dropped 3 mpg. Ethanol is for drinking, not burning.

Lanny Chambers wrote in news: snipped-for-privacy@newsclstr02.news.prodigy.com:

Now if people would just stop polluting it with olives and vermouth and other unhealthy things...... ;-)