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Old 05-19-2012, 04:13 PM   #1
Scooby Specialist
Member#: 3251
Join Date: Dec 2000
Chapter/Region: NWIC
Location: Buckley, WA
2009 WRX Hatch

Exclamation Fuel brand sensativity? 76 wins.

I like checking in on my Fine Learning Knock Correction table every once in a while just out of curiosity (my wife attributes it to paranoia).

Normally I fill up with 76 as they are the only station left in my neighborhood that doesn't have the "May contain up to 10% Ethanol" stickers.

On my way out of town I filled up with Chevron, I don't recall ever having an issue with them. However, after our trip, I checked the table and hmm... there's one cell starting to show a correction. Normally my car is all zero's across the table and IAM is always at 1. I'm on a stock tune apart from lowering the values for the OL/CL delay, which the car has always been happy with.

So then after the tank of Chevron, I filled up with Shell on my way home...Maybe the marketing got to me.

My question then is does 20% more "Nitrogen" in their new formulation = 20% more knock? I think the numbers speak for themselves. Could this have just been a bad batch? I don't really want to ever try again to find out.

Here is my log of condensed Learning View readouts. Ever since I switched back to 76, my FLKC table has stayed at 0 in all cells.

04/18 Chevron
04/24 Chevron -1.05 @ 2.0-5.0 @ 4400-5600
04/26 Chevron -1.05 @ 2.0-5.0 @ 4400-5600
04/29 Chevron -1.05 @ 2.0-5.0 @ 4400-5600
04/30 Chevron -0.70 @ 2.0-5.0 @ 4400-5600
04/30 Chevron -0.70 @ 2.0-5.0 @ 4400-5600

Fill up with Shell

05/02 Shell -0.70 @ 2.0-5.0 @ 4400-5600
05/03 Shell -0.70 @ 2.0-5.0 @ 4400-5600
05/04 Shell -0.70 @ 2.0-5.0 @ 4400-5600

05/07 Shell
-1.05 @ 1.3-1.6 @ 3200-4400
-2.10 @ 2.0-5.0 @ 4400-5600

05/08 Shell
-1.05 @ 1.3-1.6 @ 3200-4400
-2.10 @ 2.0-5.0 @ 4400-5600

Mileage on car readout is 19.2.
Normal for me is 22.5

05/08 Shell - RESET ECU after 1/4 tank.
05/08 Shell 0 FLKC after 2 drives.
05/09 Shell 0 FLKC
05/10 Shell -1.40 @ 2.0-5.0 @ 4400-5600

05/10 76 Reset ECU add Gumout Fuel Injector cleaner and fill up on 1/8th of a tank with 76.

05/11 76 0 FLKC
05/17 76 0 FLKC 3/4 tank through.
05/19 76 0 FLKC

Does anyone else see this kind of fuel sensitivity between brands? Chevron, Shell and 76 are all considered "top-teir". While 76 does contain cleaning additives, my car appears happier with them. It seems to me like the less additives, the better. I'm almost considering trying Safeway or Arco (no additives) as a test, but I'm pretty sure they are all using 10% Ethanol as well, which could be unrelated though. Ethanol is supposedly what they use to control octane anyway.
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