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Old 07-17-2009, 05:07 PM   #4 (permalink)
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micondie's Avatar
Join Date: Mar 2009
Location: Western Mass
Posts: 104

moby van - '03 Dodge Caravan SE
90 day: 19.74 mpg (US)
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The only time using premium makes sense is if you can advance your timing on premium and get better mileage. I have a Trans Am that calls for premium but it will run on regular. The computer just backs off the timing to compensate. This loss of power is noticeable when you drive it. I haven't done any mileage checks one vs the other but I would assume the mileage also drops. I remember reading a new car test back in lthe 80's when no-lead gas was first introduced, and they tested two Oldsmobiles, one needed high test, the other has it's compression reduced to run on regular unleaded. The high compression one got better mileage, more than enough to compensate for the extra cost of the high test.
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