Flex sensor off 6.6%

[marksrig]

I tested the fuel from my tank after a long drive to make sure it was mixed well. It's a return system and I put about 75 miles on it. My sensor reads 78.4% but my Super tester says I'm E85 and the fuel in my drums test to E85.
I've had to adjust the 100% and interpolate down to get my stoich on E85 to be correct. This is the second sensor I've tried and I don't think there is a calibration besides the stoich table.
Maybe this is why GM only goes to 80.03% in the tune.
My percentage is stable while I drive and adjusts with .1% difference so I don't think it's bubbles. The sensor is on the return line #6

LTFTs look a little rich on the log because the car soaked at the store before the log. Previously all were -1

Any ideas?

E67 ECM

Mark

TTTTTTTTTTTTTTTT.hpl

FINAL FINAL FLEX FUEL TUNE.hpt

[5FDP]

Beats me but if can notice a difference with 6%, you are one special person. Anything above like 65-70% is going to act the same when it comes to pump fuel. The E98 stuff in a barrel is a different story.

[marksrig]

Oh I wasn't noticing any difference in performance, just the discrepancy. I knew I was putting E85 in and seeing something else.
On a side note, I can get E98 for like $4 a gallon in Portland. Not sure if I want it tho LOL.

[Ben Charles]

Trust the sensor over those bottle testers…

[marksrig]

I would except the sensor hasn't given me a good reason to trust it. Displayed 10% exactly on pump, so did the bottle tester. 5 tanks later with E85 from a barrel and it reads 78.4%, bottle reads exactly E85.
Car LTFT were -1 on pump. 5 tanks of E85, LTFTs were well lean at over +10 before adjusted the stoich table to get it inline. Something just seems off.
I'll test the Hz output of the sensor if I can. I have a DVM with Hz function and access to an oscilloscope.