Observation – Anyone else experience this?
 

I made an interesting observation on my RX-8 today and wanted to see if others experience this. When I first start the car and drive it for about 10 minutes the gas gauge drops about a 1/16 of a tank, it is a very noticeable drop.

At first I wrote it off to a glitch in the gauge, maybe after it warms up it registers different. Then this morning it hit me that this is not the gauge but the car is consuming huge amounts of gas during the warm up. I’m in Chicago and it has been 24 to 40 degrees over the last few weeks. The car is also in its break in period. This would also fall in line with the very poor gas mileage 12 mpg I have been getting.

Any one else experience this?

I have not noticed that, but I am one of the owners that have always gotten within EPA MPG. The fuel gauge also is not really a great way to track fuel consumption. Take a look at the pic; there are 21 marks on the fuel gauge. When I am around that low it takes about 14 ½ gallons to fill up. That means one notch is less than a gallon and it is not inconceivable to use ½ gallon in the first 10 minutes on a cold engine.

I notice this all the time. Warm up does seem to consume quit a bit of gas. Dont know why but it does and does it often. Expo's theory seems to make sense as well.

the guage always drops a little after start up. the main reason for this is the shifting of fuel from one side of the saddle bag to the other

Why would it shift any more after start-up then before the last shut down?

i dont know why it just is. it may be that the fuel equalises when you shut down and it does the evap test and the guage just doesnt change until you start it again. its been noted before by many people. some times people note that it goes up a little.

but let me correct an impression i may have left. i did not mean to imply that the car isnt usign alot of fuel in your situation. the car is in open loop until it gets to normal operating temperature. it uses much more fuel in open loop then it does in closed loop. thats why alot of short trips during the day (driving around the corner and back) can have such a huge impact on your normal city mpg.

Just a thought, but you might try noting down where the needle is at after you get home and are done driving for the day, then compare that to what you see in the morning.

Like expo said, though, those fuel gauges aren't very accurate measures. :)

I swear when I leave my car in the morning to go to work and come back to it in the afternoon the guage is lower than when I left it.

I don't think the guage is real acurrate. I experienced the above as well as it being higher upon my return then when I left the car..