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I just want to say I have a SG that could help me answer my question if I just knew how to work it entirely... I have seen miles left in tank and that sort of thing.

Anyway, I just filled up today and was very surprised. Every time but today I have gotten a pretty consistent warning at a certain point (I just asked Wiki Answers and the capacity is about 12 gals.) so I am thinking that at about 9 gals I get a blink off and on warning light.
It will esp. be lit when I get to that point and also as I am going up a steep hill. At a certain point I get a light that stays on.

Today I fueled up and it was already at almost 10 gals and I only saw it blink off and on a few times. I even asked the guy at the station about it. He couldn't believe I didn't know the tank capacity of my car! But anyway, he said they check them once a year.

I could sure find another station but heck they are the cheapest around and also they trust me so that I can fill up and then pay after I fill. Anyway, I could really check this?
I want to know if my gauge is off or if it might be them?

--des

Hi Des:

___The 03 – 07 Corolla’s tank spec is 13.2 gallons. From MT, they will hold ~ 15.x something IIRC. I top off everything because I do not have any confidence in accuracy from a first click no matter if it’s the same pump at the same station on the same day. Not that I would expect anyone else too given there are a number of caveat’s but over 5 + tanks, it doesn’t matter if you are over or under by a gallon or two at each fill. It all averages out after a few tanks are complete.

___You can find your tank cap in the owners manual and from MT, you will probably be able to add another 2 - 4 gallons over listed cap. Other then the North American Prius-II owners and that #$% ^)@$ Toyota bladder :angry:

___Good Luck

___Wayne

I think this is the key info. Also knowing I have about 13 gal tank helps as well.

Thanks,

--des

Hi Des:
it doesn’t matter if you are over or under by a gallon or two at each fill. It all averages out after a few tanks are complete.

____Wayne

My experience is that fuel gages are not linear. You read full until you have used 90% of your tank. Then a reading of 1/2 is really 65% left in the tank. By the time you are at 1/8 of a tank by the gage it is really about 17% left in the tank. This is with GM cars.

I think this is a way to force consumers to fill up sooner to prevent them from running out of gas. I usually wait until I see the warning light (1/8 tank by the gage).

I was wondering about that. I usually wait til I see the warning light too. Since I have not run out of gas in recent memory nor come anywhere close to the 13 gals for fill, I gather I am ok,
even if the gas light seemed a little slow. Another thought occurred to me: That I actually had a warning light sooner. And that I was not really aware of it as I was looking more at the SG.
Since it is off and on initially, I could have looked at the gauge exactly when it was not lit up.
I knew what day I was filling up so no harm done.


BTW, I know SG will tell you how much gas in your tank-- I have gotten to it accidently. How do you get there on purpose?


--des

My experience is that fuel gages are not linear. You read full until you have used 90% of your tank. Then a reading of 1/2 is really 65% left in the tank. By the time you are at 1/8 of a tank by the gage it is really about 17% left in the tank. This is with GM cars.

I think this is a way to force consumers to fill up sooner to prevent them from running out of gas. I usually wait until I see the warning light (1/8 tank by the gage).

BTW, I know SG will tell you how much gas in your tank-- I have gotten to it accidently. How do you get there on purpose?


Go to the screen that shows the mileage for the tank and then cycle through the different readouts under that. You'll find such things as tank mpg, average speed, max speed, max coolant temperature, gallons used, gallons left, distance traveled, and distance left (extrapolated from the current tank mpg using the gallons left).

If you are not sure how to get to that, press the home button, then the button next to "Trip". The only two I usually use are "Current Trip" and "Tank", but you also have "Yesterday" and "Today" (among others).

I'm not a fan of running the tank too low. The fuel pump is at the bottom of the tank, and is cooled by the fuel sloshing around it as well as flowing through it. Running on empty (there's a song in there somewhere) shortens it's life.

Disclaimer: Haven't tested yet, so check back to see if I change my answer.

Go to the screen that shows the mileage for the tank and then cycle through the different readouts under that. You'll find such things as tank mpg, average speed, max speed, max coolant temperature, gallons used, gallons left, distance traveled, and distance left (extrapolated from the current tank mpg using the gallons left).

If you are not sure how to get to that, press the home button, then the button next to "Trip". The only two I usually use are "Current Trip" and "Tank", but you also have "Yesterday" and "Today" (among others).
That will tell you tell you how much is left if the Tank size is entered correctly. If you want the raw numbers from the car's computer (since you have a ScanGauge) try sending the OBD-II command to read current fuel level (from the fuel sensor) if it's supported over OBD-II on your car.

MORE>MORE>CMNDS>(MEMORY 1)EDIT>012F>OK>SEND

What you should get back is something like:

412F8B

The last two digits (in this example "2B") is the tank-full percent in hex 0xFF is full 0x00 is empty. Here's the decoder ring:

FE-F0 = 99%-94%
EF-E0 = 94%-88%
DF-D0 = 87%-82%
CF-C0 = 81%-75%
BF-B0 = 75%-69%
AF-A0 = 69%-63%
9F-90 = 62%-56%
8F-80 = 56%-50%
7F-70 = 50%-44%
6F-60 = 44%-38%
5F-50 = 37%-31%
4F-40 = 31%-25%
3F-30 = 25%-19%
2F-20 = 18%-13%
1F-10 = 12%-06%
0F-00 = 06%-00%

Now that is really interesting! I'll have to try that. Too bad we can't program that into the SG for easy readout. :(

So looking at the range we have 240 unique readings for level. Dividing 100 by 240 gives 0.4166(repeating) as a multiplier...

So taking the example above (the top one) where the significant characters are 8B, conversion to base 10 gives 131 * 0.4167 = 55% (rounded up)

Likewise 2B would be 41 * 0.4167 = 17%

Have I got it right? If so I can write a small program to plug the number into... if I can remember the code to put in every time. Much better than my current process of estimating from needle placement on a gauge with only 3 marks on it anyway! (F, 1/2, and E are not very fine markings on that gauge. :()

Well the trick is support. I'm not certain my car supports it.

The return you get back must start with 412F if it doesn't, SGII is reading a return from another request instead of 012F

The process (for CANbus cars) is documented here:
http://en.wikipedia.org/wiki/OBD-II_PIDs

ohh, and the multiplier is 0.3922 or 100/255

<11011011>

Fuel gauges in my experience aren't that accurate inasmuch as a previous poster said they're not linear; but I've found them to be pretty consistent. In other words, on the same commute, you'll go about the same amount of miles to get to the same readout on the gas gauge from tank to tank.

Wow! A decoder ring for the SG. I'm not sure I'm fully awake enough to handle all that. :-)

--des

Well the trick is support. I'm not certain my car supports it.

The return you get back must start with 412F if it doesn't, SGII is reading a return from another request instead of 012F

The process (for CANbus cars) is documented here:
http://en.wikipedia.org/wiki/OBD-II_PIDs

ohh, and the multiplier is 0.3922 or 100/255

<11011011>

I've not tried it yet...

LOL I used base 15 instead of 16 for the conversion to base 10! Oops! I was mighty confused there for a moment!