Loss of fuel economy - Ford Powerstroke Diesel Forum
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Old 07-17-2008, 05:54 AM
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Loss of fuel economy

Been reading on here about loss of fuel mileage, seems like the first question is always, have you changed fuel filter? Seems to me like if fuel filter was bad, it would suffer from lack of fuel and run bad. If it runs good not starving then how does a new filter help? Just trying to get my head around this. I ask because like so many others I have seen my mileage drop from about 18 down to about 12. I have a 01 with superchips, afe intake, 4" exhaust and 220,000 miles. I just did a tranny but the mileage drop was before that and did not improve after. I have been blaming it on the low sulpher fuel but after reading on here starting to wonder. I checked for codes and not showing any. I do drive it like I stole it , but I always have, so not sure why it would change so drastically. One thing I have noticed is at low rpm acceleration I get a good bit of black smoke. Like if i get on it a little hard at a light or if I get into it alittle hard at 50 in overdrive, don't remember it having this much smoke before. Clears up as soon as the rpms come up alittle. Turbo boost is still showing about 21 on hard acceleration running empty and higher under aload so think turbo is ok. So I guess after reading all that I have I am going to check ebpv for soot build up and change fuel filter. Still can't get my head around how the fuel filter would decrease mileage, seems if it were dirty it would allow less fuel to flow and decrease it, but since I have'nt changed it in over 100,000 miles I think its probably due. I'll post back as to what happens.
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Old 07-22-2008, 12:52 PM
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Quote:
Originally Posted by shock41 View Post
Been reading on here about loss of fuel mileage, seems like the first question is always, have you changed fuel filter? Seems to me like if fuel filter was bad, it would suffer from lack of fuel and run bad. If it runs good not starving then how does a new filter help? Just trying to get my head around this. I ask because like so many others I have seen my mileage drop from about 18 down to about 12. I have a 01 with superchips, afe intake, 4" exhaust and 220,000 miles. I just did a tranny but the mileage drop was before that and did not improve after. I have been blaming it on the low sulpher fuel but after reading on here starting to wonder. I checked for codes and not showing any. I do drive it like I stole it , but I always have, so not sure why it would change so drastically. One thing I have noticed is at low rpm acceleration I get a good bit of black smoke. Like if i get on it a little hard at a light or if I get into it alittle hard at 50 in overdrive, don't remember it having this much smoke before. Clears up as soon as the rpms come up alittle. Turbo boost is still showing about 21 on hard acceleration running empty and higher under aload so think turbo is ok. So I guess after reading all that I have I am going to check ebpv for soot build up and change fuel filter. Still can't get my head around how the fuel filter would decrease mileage, seems if it were dirty it would allow less fuel to flow and decrease it, but since I have'nt changed it in over 100,000 miles I think its probably due. I'll post back as to what happens.
For one, when it comes down to any kind of filter for any kind of engine, it's all about flow. Over time, your fuel filter accumulates all sorts of foreign debris in it's media. When the fuel filter(or ANY filter)isn't changed on regular basis, the debris will cause a restriction in flowing the fuel, causing you to get crappy mileage. Another thing that'll cause poor fuel mileage is when you "drive it like you stole it". Just like any engine, it's gonna get crappy mpg if your constantly standing on it. I'm not saying to drive like an old lady on her way home to watch Matlock, but tone down the speed & you'll notice a slight difference. Your smoke: it's probably from the SuperChips. It's doing it's job. It's just increasing your fuel intake to the injectors. The black smoke @ low RPM is just unburnt fuel. And for your turbo; you really don't wanna "guess" if your turbo's ok. If you're really concerned, take your intake arm off & look @ the condition of your compressor wheel. If you want to anal retentively check your turbo, pull it off & check your bearing, oilers, turbine, etc. My advice to you: if you want to keep your truck in "drive it like you stole it" condition, give it a little more love. Change all of your fitlers regularly. It's sounds like you're beating the snot out of it.
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Old 07-22-2008, 01:08 PM
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if you have not changed fuel filter in 100,000 miles you are gonna have a lot more problems than just fuel mileage.that is called lack of maintenance,and is horrible for that truck.I would never purchase a truck that you have owned!!!!!!!!
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Old 07-22-2008, 01:11 PM
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i have an 02 and notice similar conditions. i have 268k, at around 230-250 i got between 15-17mpg in the city and drove pretty normal, a little fast, nothin serious, now w/ a chip intake exhaust and drivin like slow as crap, i cant get better than 15. maybe compression loss, or injector o-ring leakage!!! in the mornings, florida mornings, at 8 or 9, she starts rough and spits out white smoke kinda thick for 20 or 30 seconds, once shes warm she runs good. i know some people say on cold starts, they blow a little smoke, but ive never seen it before on mine except in the real cold winter. its july i live in south florida, its friggin hot!! whats the deal!!
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Old 07-22-2008, 01:34 PM
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I noticed mine has dropped mpg over the last few months as well. Everything runs fine and I change the oil and fuel filter on time everytime. I pulled a 16' utility trailer empty about 3 months ago doing 70mph aver for about 600 miles and got 11 mpg. I just recently intalled a AFT Stage II intake, 4" TB exhaust and a TW chip. I'm making the same trip I did a few months ago this weekend and hope I get some better millage if not I have no idea. I would like to think I could get better mpg than that pulling an empty trailer.
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Old 07-22-2008, 04:34 PM
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you will get better mileage for sure,my truck with almost the same mods gets 20-22 at 65 or 70 mph that is empty of course.
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Old 07-23-2008, 04:41 AM
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Ok I have changed the filter and went ahead and put on a new air filter too. Ran a tank of fuel thru it, checked the mileage manually, topped the tank before and after and divided mileage by gallons. 12.3 miles to the gallon. As for maintenance, I change all fluids at or before recommended intervals, oil every four thousand with synthetic. Antifreeze and tranny every 50,000, and fron and rear differentials every 100,000. Have replaced both front wheel bearings, all new brake calipers and rotors at 200,000. As for drove it like I stole it, I say that because I have always drove the truck the same, I don't worry about getting over 2000 rpm I drive it like I would any other automobile. This is my third powerstroke, I have gotten well over 300,000 miles out of all of them and I did not do that by abusing or not taking care of them. My first two I changed the fuel filters every 15,000 miles religously. For some reason on this one I havent. Both of my old ones I did see a decrease in mileage after they had high mileage but only a mile or two to the gallon not 6-7 like this one. As for the fuel filter, my original question was if the fuel filter is bad "media full of trash" it seems like it would flow less fuel causing a running problem or starvation of fuel so how does that equate to more fuel usage?
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Old 07-23-2008, 07:34 AM
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Quote:
Originally Posted by shock41 View Post
As for the fuel filter, my original question was if the fuel filter is bad "media full of trash" it seems like it would flow less fuel causing a running problem or starvation of fuel so how does that equate to more fuel usage?
It's basic science, brother. You have fuel trying to makes it's way through a clogged filter. The resistance from the ca-ca in the filter is going to decrease your fuel flow. You still have fuel going to the combustion chambers, but a smaller volume due to the decrease...ya with me? In turn, your engine needs to compensate for the demand of however much throttle you give it, making it work harder & decreasing mpg. When you have a consistent flow with a clean fuel filter, it needs little to no compensation. I'm sure a REALLY clogged filter would cause starvation, but the earliest warning signs are decrease in mpg. There's no other way I can explain this unless someone else knows more/can describe better. Take my word for it, bro!
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Old 07-23-2008, 08:22 AM
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it also is extremly hard on fuel pumps and the whole fuel system,take for example if you put in a chip you are dumping more fuel but if you dont drive it on the floor you will get better economy because you are using less throttle to drive the truck,same with a clogged filter you are not getting adequit fuel burn,therfor you are more in the throttle to go up the same hill that you were going up before but before you were using less throttle.
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Old 07-23-2008, 08:35 AM
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I don't know if this applies to Diesel computers but it does in Gas engines. Computers pick up Throttle position to determine timing, shift points and fuel. If your filter is clogged and your are using 20% more throttle position to get the same power the computer may be adjusting the shift points and timing affecting your MPG. Just a guess from a gas guy.
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