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Old 02-01-2019, 10:37 PM   #7 (permalink)
Master EcoModder
Join Date: Aug 2018
Location: USA
Posts: 299

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)
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They weren't necessarily falling apart, but they weren't great either. There are lots of variables in play which are hard to measure. It is kind of hard to do ABA testing most of the time, so I try to deduct what I can from my fill ups. I suppose I should pay attention to confirmation bias. That being said, I think they did make a difference.

The roof racks did make a nice difference when I took them off. I think it was about ~1mpg.

That's fair to say it probably wasn't 12%. I think I do remember reading that larger spark plug gaps require more electricity to maintain. I did gap them larger because I've seen sources saying that a larger gap will cause better combustion, but it isn't very clear if I've seen an improvement in FE because of it.
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