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gas mileage suffers with tune

2252 Views 8 Replies 3 Participants Last post by  WHY
i am definetly not seeing the 1-3 mpg increase. the one time a few years ago that i gauged it was 19 mpg on the freeway with cruise control. i have recently cleaned the throttle body, changed my spark plugs and did a seafoam treatment. on top of that, i ordered the custom tuned pcm. i'm lucky to get 18 mpg freeway mileage with cruise control. i get about 15 in the city. i'm going to swap it out with the original this weekend, tank up and see how my mileage is on the next fill up.

except for the hit on the mileage...i love the tune for the performance. i have nothing bad to say about that. even my bro likes the difference from stock.
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did you do the core program or the loaner program. if so did you did a CASE relearn? if not you gas millage will stink
did that at the dealer.
core...i have the original.
i am not sure then:weird:. hopefully some will else will come up with a better idea. my other idea about the cause would be that with the tune you are harder on the car on accelerations and driving in general because of the new found performance and this is causing the mpgs to decrease
not so much...on a few road trips that i have taken, i was careful and not to gun it for a full tank of gas. i set the cruise to like 5 or so above the posted limit and just cruised.
it's a mid-year 2004 and only have 66k in mileage
not so much...on a few road trips that i have taken, i was careful and not to gun it for a full tank of gas. i set the cruise to like 5 or so above the posted limit and just cruised.
how fast were you going? the optimum speed for the good mpg is about 55/60 if you were going 75 the most of the way even with cruise control it would hurt mpg
i probably had it set to 75 most of the way.
that is ten over them I 5 high limit and twenty over the open road like 99 E or W no wonder
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