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Fuel gauge: 1 mark = ? gallon

Old 07-31-2011, 02:54 PM
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Fuel gauge: 1 mark = ? gallon

How do you guys measure the gas consumption with your fuel gauge? I know it's not linear, but roughly, 1 mark on the gauge represents for how many gallons?

I try to keep note with MPG and after a 250 mile trip(hwy), the gauge point falls from 3/4(5 or 6 marks below F) to 3 marks above E, and the warning light comes up. So any one could help me with the math. LOL

Thx
Old 07-31-2011, 03:10 PM
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im not really sure, theres about 15 or 16 tics on the gauge and its a 15.9gal tank so youd kind of assume 1 tick per gallon but ive gone to fill up gas with my gauge at the very bottom line and only had to put a tad less than 14 gallons in.
Old 07-31-2011, 03:19 PM
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The thread title is accurate: 1 mark = ? gallon.

Each 8 is a bit different, and due to the hump in the middle of the tank, and the sensor only being on 1 side, it's easy to get very inconsistent readings.

For mine:
Doing 100% highway long distance traveling without noticeable lateral G, the 3/4 full mark is actually about 3/4s of the way to the light on. The light comes on at the 13.1g refill mark, assuming everything is level between the two sides. The 1/2 is usually a bit past the halfway mark to the light, and the 1/4th is more like 1/5th or so left to the light. My full mark is above the top of the gauge, the light comes on just barely above the bottom empty mark. I've run it to somewhere on the actual E mark once, filling up 15.5 gallons.

But, don't take this as gospel, yours is probably different. Only thing to do is learn your own.
Old 07-31-2011, 04:02 PM
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Some cars are equipped with this electronic thing that you could see how much more you could drive until your gas empties out. This is how you will know if you could reach your destination or not, without stopping for gas.
Old 07-31-2011, 04:06 PM
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That isn't very helpful, since it isn't in any of the RX-8 model years, and this is an RX-8 forum, so the guy that started the thread probably has an RX-8.



Logically.


I could be wrong.
Old 07-31-2011, 08:03 PM
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lmao ^^ He's trying to be the top poster on the forum, he'll probably be there in about a week and a half at his rate.
Old 07-31-2011, 08:09 PM
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He is over 15,200 posts behind Jedi.

And that is just the public post count. Jedi has 46,365 total posts including lounge posts, not including posts he has deleted.
Old 07-31-2011, 08:37 PM
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The only time I really keep an eye on my level is when I get to 1/4 cause that's when I usually fill up. My guage bounces around too much to give an accurate reading of what 1 line is. If you wanna calculate mpg do what I and a few other members have done, use a fuelly account. Check my sig
Old 07-31-2011, 08:48 PM
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The system is not linear... F is not actually full... E is not actually empty.

So, there is no direct correlation between each tick mark and used capacity.
Old 07-31-2011, 09:37 PM
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Exactly. The gauge is there to help you know about how you're doing, for general planning. If you want to know mpg, record how much it takes to refill the tank. Do that over several tankfuls to get a credible average.

Ken
Old 07-31-2011, 09:49 PM
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My needle can be totally below E and I end up with like 13.5 to 14 gallon fill..
Old 07-31-2011, 10:22 PM
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never cared about mine gas gauge. I just fill up when the light is on. and keep more than 1/4 tank when autocrossing.
if you try to calculate your MPG, best way is to fill up till the nozzle click, clear your trip computer, drive till you need gas, fill up till the nozzle click.
look at your trip computer and how much you just put in the tank, theres your MPG.
Old 07-31-2011, 11:25 PM
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Though I would be the first to suggest that the gauge is NOT linear, I have seen several that work like mine does and it is almost exactly linear - 1.5 gallons per 1/8.
Just as it crosses the "E" line, it will have about 2 gallons left.
1/2 tank is 8 gallons.

I've had many occasions to pump my tank dry into jugs while I tested fuel pumps and it has always worked out exactly like this.
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