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Old 08-08-2012, 07:42 AM   #29
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Originally Posted by kam327 View Post
We're talking about 2 different things then; I was always referring to the myth of long term mileage increase due to slow and steady break in. In your statement "it takes the PCM a while to 'learn' our styles and habits" I took "a while" to mean many months and thousands of miles. Like the 3rd poster on this thread who said "At about 1,500 miles I started seeing a steady, noticable increase in MPGs." I did the non-scientific analysis to look into long-term break in which many on this forum believe in, in other words a steady increase in mileage over the first 5,000 to 10,000 miles. Doesn't seem to happen with any consistency across the board.

And that's what I meant by Craigsfocus's graph supports my theory. If you were to apply a trendline to his graph it would show a pretty flat average of 30-31 mpg over his 3 months or so of data.

I see what you're saying now, but everyone should just throw out and ignore their first tank's mileage. Most dealers "fill up" a tank for delivery but who knows how full they filled it, and if they drove it around some after filling it up. You'd have no way to know and it would throw off your first tank mpg calculation, and probably your 2nd tank's as well.
Yeah, I think we are saying roughly the same thing. I don't believe that mileage gets better with engine break-in. I give my vehicles a hard break-in (a different discussion/argument) and that would lead to me having my maximum mileage by 100 miles on the odo.

As for the PCM/ECU, that I can actually vouch for. I hand calc my fuel mileage out of old hyper-miling habit, and every time I've had my vehicle reset (mft, 12B37, mft, mft again) my mileage immediately drops back down to 26. The total mileage on the car has always been irrelevent to the mileage- my last reset was at about 3k miles.

Final note worth mentioning (if I haven't already, idk because I'm on my phone) is that changes in driving style will affect the next tank also. I have noticed this a few times-once on a long trip that I took, once with a tank with about 5 total hours of idling in the parking lot (non-ac hangar), and once after a day with 15+ dyno pulls. Each time, after a full tank of 'normal' driving, the car would climb back to my average fuel consumption.
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