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I know I don't have the scangauge dialed in exactly yet, but I'm seeing some pretty wild fluctuations in its accuracy. Now, some things I think may effect this are:

1) Two different drivers with different driving styles and driving conditions (me = hypermiling & highway, wife = normal & city).
2) Large variance in weight of the car because the wife uses it to haul things during the day.


I guess what I'm asking is will these two things effect the scangauge's accuracy that much? How accurate are your scangauge numbers from tank to tank? I've seen swings of 10%.

Hi, Daox! There can be rather large differences based on fill variation, but that does seem extreme. How much FASing are you doing? I saw a fair difference in miles shown on the SG when Laurie borrowed my car for a bit... but I think she may have forgotten to turn the key back to the on position a few times. The distance seems to be about 8mi short...

Are the swings centered about the midpoint fairly well? If not you may need some long term trending to get it sorted out.

I'm really not sure how having another driver with radically different driving techniques in the same car will affect the numbers (since I'm generally the only one who drives my car), but I do know that you aren't the only one sharing a car. Some other people can hopefully chime in here?

For the first few tanks (3-5) I saw about 10% fluctuations, but as I slowly dialed in the calibration it decreased. My last tank had a difference of 0.2 MPG between the SG and the calculated value. I have noticed larger differences when I have long highway trips versus my normal city driving.

Changing BTU levels in the gasoline at this time of the year may affect things.

I've actually had the scangauge for a few months now. So, its not the gas being reformulated for winter. Since the wife drives it during the day she usually fills it up in the city where its cheaper. She was adjusting it for a while, but only to the exact amount of the fill up every time. This gave me readings all over the board. I am doing more FASing, but I really don't go through many lights each day. I have 5 on the way to the highway which is about 1 mile. I can usually time most of the lights, if I can't I let it idle to warm up the car. These aren't long lights. Then, once I get off the highway I only have 2 lights, and I FAS for them. I guess I'll just have to start tweaking until I get it closer.

Here's a few things to consider or check.

On my Tacoma if I a FASing my fuel usage still will show .1gph instead of zero, but on my Element it shows 0gph correctly. The more I FAS my truck the more it produces a discrepency which if I'm consistent in my FASing from tank to tank will be compensated by the tank adjustment, but If a end up traveling a long highway tank with no FAS I will be way off.

If you do a lot of ICE on engine braking it will also incorrectly show significant fuel use even though you are most likely in fuel cutoff.

See if you can look at injector time instead of gph. If you
can and you see that go to 0 during FAS, then Ron still has
work to do. Unfortunately some ECMs report nonzero even when
they're in fuel cut, so it's not entirely his fault.
.
_H*

I did recently change it to Hybrid mode. But, before that I wasn't doing any engine off anything.

My understanding from the instructions is that you are only to do the tank adjustment ONE time, the second time you fill up. This may explain it! :)

My understanding from the instructions is that you are only to do the tank adjustment ONE time, the second time you fill up. This may explain it! :)

Woah hold up, my understanding was that you do it every time you fill you. So if you put in 14.3 gallons of gas and the scangauge thinks you put in 14.6, you turn it down some and fix that.

Seen this: http://www.cleanmpg.com/forums/showthread.php?t=6074 ?

It might be of some help.