Mine drops off a mpg or 2 when doing 60+ in 10th gear. It's happiest in 8th at those speeds. Barely makes any boost unless going up a small hill.Fyi sport mode on an auto 3.73 bronco locks out 9th & 10th gear. This is actually lower gear ratio than 10th gear with 4.70 on sasquatch broncos. Mileage doesn't dive off as bad as people seem to think, I have been a solid 17-18mpg with both my broncos.
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