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Old 07-19-2011, 05:14 PM   #14 (permalink)
graydonengineering
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Join Date: Jul 2011
Location: Tucson, AZ
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Frontier 2wd 2.4L 5 speed - '98 Nissan Frontier XE
90 day: 27.87 mpg (US)
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Quote:
Originally Posted by WVengr View Post
Well may have found the problem. I was reading the user manual to see if there was a thing in maintenance that I had forgot. Instead I saw "Fuel: Recommended 91 RON" Since I had a 150 mile trip to make I topped off the tank with 93 octane just to see if the recommended made a difference. I filled up again when I got home 159 miles later and shattered my old mileage record

EDIT: I thought I got 32 MPG, since that's where the gas pump shut off. However this morning I noticed that the gas gauge was down a bit even though I had just driven a few miles back to my house after filling, so i filled up again this morning, this time at the same station I had used when i left, and got a little over a gallon more in, so it is looking more like 26 MPG, but still a marked improvement.

It wasn't knocking so I hadn't thought about octane, but for some reason it made a difference. Not sure why though. Further research is needed to see what octane gives me the lowest $ per mile. Not exactly sure how to do scientific testing on this without draining the whole tank though.
Higher octain is more important in the summer as the higher temps encurage pre detonation. You may be able to get away with running lower octane in the cooler months and swithcing back to high in the spring.
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