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MPG Experiment

Old 04-09-2012, 11:55 PM
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Default MPG Experiment

Ive seen a lot of "mpg" threads on here, basically "what can I do" and "whats the problem" type questions. Well by accident, and a month long "experiment" Ive found a way for better mpg's. I know this will sound crazy as did I, but so far it has proven correct. I get 15-17 mpg, I had to stop and get mower gas and while I was at it, top off the 3/4 tank I had in the Jeep. Something didnt seem right so I figured the milage and I had got 20 mpg,WTH! So I started topping off anywhere from 1/2 to 3/4 and so far Ive got 19,21, and 20 mpg's! I told you it would sound crazy. For some reason, a full tank runoff only gets me 15-17 mpg. All I can figure is the engine is somehow running more efficient with the extra weight.
I would like to have some volunteers with their daily drivers to try this for a month and report back your results, or offer up some explanations,hope to hear from you all on this, Thanks!
Also, this is a stock 2000 XJ with 135k and auto tranny

Last edited by trakr; 04-09-2012 at 11:58 PM.
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Old 04-09-2012, 11:58 PM
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it is true that less weight is gonna get you better mileage.

but idk bout 2-3mpg..
im guessing it has more to do with the type of driving your doing
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Old 04-10-2012, 12:18 AM
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I heard that cars tend to run better if there is more fuel in the tank. Don't know why, but I heard that before.
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Old 04-10-2012, 12:22 AM
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Any chance you pump has a bad check valve? Does it take a while cranking the engine in the morning to get the engine to start?
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Old 04-10-2012, 12:40 AM
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I've actually read this elsewhere and have to say, I've noticed that I get better mileage using only the top half of the tank as well (rather than using the whole thing). It makes no sense at all, weight is the enemy of mileage and dragging around 60-120 pounds of liquid should result in poorer fuel economy than dragging around 0-60 pounds... but it doesn't.
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Old 04-10-2012, 12:41 AM
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Black magic!
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Old 04-10-2012, 01:08 AM
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Originally Posted by 96rokee View Post
it is true that less weight is gonna get you better mileage.

but idk bout 2-3mpg..
im guessing it has more to do with the type of driving your doing
You misunderstood, Im getting better milage keeping the tank full than running the tank from full to empty
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Old 04-10-2012, 01:10 AM
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Originally Posted by F1Addict View Post
I've actually read this elsewhere and have to say, I've noticed that I get better mileage using only the top half of the tank as well (rather than using the whole thing). It makes no sense at all, weight is the enemy of mileage and dragging around 60-120 pounds of liquid should result in poorer fuel economy than dragging around 0-60 pounds... but it doesn't.
Common sense tells me the same thing, but its not happening in this case.
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Old 04-10-2012, 01:12 AM
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Originally Posted by DualSportDad View Post
Any chance you pump has a bad check valve? Does it take a while cranking the engine in the morning to get the engine to start?
Nope, starts first cank,purrs like a I6 should
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Old 04-10-2012, 03:03 AM
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The only remotely, possible conceivable explanation is that the rip off artists that have us by the ***** selling us this crap, designed there pumps/tanks so when you are not "receiving a full load" less of the undesirable portion is being pumped into the rear of your Jeep. The ethanol/water portion separates.
Attached Thumbnails MPG Experiment-101_0023.jpg  
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Old 04-10-2012, 03:40 AM
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topping tank off actually adding more than gauge goees like 1/8 to 1/4 more fuel try stopping on full mark every time then check numbers...
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Old 04-10-2012, 04:21 AM
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Originally Posted by freegdr View Post
topping tank off actually adding more than gauge goees like 1/8 to 1/4 more fuel try stopping on full mark every time then check numbers...
Gauge has nothing to do with miles driven divided by gallons used. I filled up, drove 120.1 miles and it took 5.995 gallons to top it off. If the guage didnt work at all, those numbers wouldnt change. I use to always fill up at around 240 miles, which it took a little better than 15 gal. to refill, thats about 16mpg. Yesterday I filled up with a little over 7 gal. at 143 miles, thats right around 20mpg. Like I said, I know it sounds crazy, but the #s dont lie.
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Old 04-10-2012, 04:28 AM
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Originally Posted by trakr View Post
Gauge has nothing to do with miles driven divided by gallons used. I filled up, drove 120.1 miles and it took 5.995 gallons to top it off. If the guage didnt work at all, those numbers wouldnt change. I use to always fill up at around 240 miles, which it took a little better than 15 gal. to refill, thats about 16mpg. Yesterday I filled up with a little over 7 gal. at 143 miles, thats right around 20mpg. Like I said, I know it sounds crazy, but the #s dont lie.
what im saying is stop when needle hits full then drve then fill to same spot on gauge it will be more acurate
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Old 04-10-2012, 05:21 AM
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Originally Posted by freegdr View Post
what im saying is stop when needle hits full then drve then fill to same spot on gauge it will be more acurate
Hows that different from doing a complete fillup? A complete fillup is easier to obtain than trying to monitor when gauge reads full.
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Old 04-10-2012, 05:25 AM
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Originally Posted by trakr View Post
Hows that different from doing a complete fillup? A complete fillup is easier to obtain than trying to monitor when gauge reads full.
are you filling to exact same spot in tank every time?
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