4.6 bad mpg?.... - F150online Forums


4.6 bad mpg?....

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  #1  
Old 07-04-2011, 09:16 AM
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4.6 bad mpg?....

Hey guys, i have a 99 xlt 4.6 2wd
in the past 3 months, ive replaced the fuel filter, had a full fuel injection cleaner service, full tune up with all new spark plugs and wires, switched to ethanol free gas, and the Gotts Mod, but i still cant get above 14mpg... i know that since i cruise to and from work about 30 miles a day at 75mph that cuts it down but i wouldnt think by that much.. any help?
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Old 07-04-2011, 11:24 AM
glc
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Did it USED to get better mileage driven the same way? if so, how much?
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Old 07-04-2011, 12:46 PM
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you have larger tires than stock? added weight to the truck? keep those rpm's under 2k and you should get a little bit better gas mileage.
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Old 07-04-2011, 02:56 PM
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the only added weight is a 10 inch sub and 1200watt amp and the tires are 255/70/16 instead of 235/70/16 so only like half an inch bigger
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Old 07-04-2011, 02:56 PM
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its never gotten good gas mileage since i got it in february
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Old 07-04-2011, 03:17 PM
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Just keep your foot out of it. I'm currently getting 17mpg when hauling close to 1000lbs with a combo of city and hwy, but I also have a cai, custom tune and exhaust, and I'm lowered too.
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Old 07-04-2011, 06:19 PM
glc
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Quote:
Originally Posted by ZW1991 View Post
its never gotten good gas mileage since i got it in february
Then you don't KNOW that something has happened to cause the mileage to be bad. What you are getting is not out of what may be normal. My son in law has a 98 4wd with a 4.6 and the best he's EVER seen is 15 on the highway at 65. He gets 12 commuting.
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Old 07-05-2011, 01:21 AM
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i KNOW that. thats why im asking for help to figure out what it might be
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Old 07-05-2011, 04:31 AM
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It might be NORMAL for your particular truck and driving habits.
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Old 07-06-2011, 08:11 AM
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the tires throw your speedometer off a little bit so its not completely accurate.
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Old 07-06-2011, 08:12 AM
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i know, but its not by very much
i can explain how i hope i figured it out, but if i calculated it right, im actually getting .58846mpg more than it shows due to tire size dif if that was the only factor, but there's also rolling resistance, tire tread, and weight.. all things aside that means i still havent gotten any better than14.6mpg

Last edited by ZW1991; 07-06-2011 at 08:55 AM.
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Old 07-06-2011, 11:49 AM
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I get about 15.6 mixed city and highway '97 4.6 4x2 3.55LS. Might just be your particular truck if its been maintained ok...
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