More MPG ??

[Diamond B Ranch]

I know, it gets asked all the time, but here goes mmy rendition. Our 2000 crewcab 4x4 auto has lost mileage from a previous of around high 17 to 14 MPG. The truck is stock with no mods and the fuel filter has been replaced twice in the last 6 months since we noticed the slip in mileage. My wife drives it as her daily driver and her habits have not changed. We currently have BFG AT's that are about 1 inch taller than stock and the truck has 189k on the odometer. We just got it from the shop. They got no codes and said the sensors all seem to be reading. The mechanic ran the engine self diagnostics several times and occasionally got "#8 cylinder not contributing". He emphasized that this was not a continually thing. AS far as I know the engine has had no work done to it so everything except the water pump is original (minus filters, oil...). Could the #8 cylinder thing be a precursor or indicator of bad injectors or is there another possibilty to explain the loss of mileage. The only other contributing factor I can think of is, that I ran a re-useable air filter for a while and when I cleaned and re-oiled I think I over oiled it. There was excess oil in the bottom of the air box. Could this be causing the sensors downstream of the filter to be sending bad data and not showing as bad?

 

[Sleeper Diesel]

as far as the #8 cylinder is concerned. the stock fuel system on the 7.3 is a dead end system and usually the #8 cylinder is starved for fuel. which is on all 7.3. i dont know were you are from but i know its getting colder and the trucks need longer to heat up and the hotter it gets the more effiicent it runs. that is why some guys run a 203 degree thermostat in there trucks. im new to this stuff. but this is what i gathered hope it was helpful

 

[Scarlet_Nape]

DBR,

There are several things you can try, depending on how much money you want apply to the mileage improvement.
One of least expensive is to upgrade the intake using the DIY (Do It Yourself) Tymar. The stock airfilter/boxes are not the best filters, and several experts advise against using any K&N filters, or similar products. Now, if you are willing to pay more money the AFE Stage II intake is considered one of the best on the market. Server users on this board have one and love them.
The second option is upgrading to a chip/programmer. DP-Tuner and Tony Wildman are considered two of the best. Call 'em and they can tell you what they can do for you. As soon as I get some gauges for my truck, I will be calling them. (Mod money is hard to come by, these days! )
Lastly, I have heard of some pretty good mileage increases by adding a regulated return kit. This could help with your #8 falling off.

Hopefully, this will help you with some direction. I'm sure some more of the guys will offer their opinions, shortly!

I hope this helps, but be forewarned...once you get PMS (Powerstroke Mod Syndrom) it's impossible to cure. You will only be able to maintain it with a fat wallet!

Welcome aboard, and please post all of your questions, and we'll happy to answer what we can.

 

[DaveBen]

Winter Diesel fuel gets less mileage over Summer fuel. I don't know it they are running winter fuel where you live. They are not here yet.

Dave

 

[hheynow]

I'm not too familiar with the super duties, but in the 94-97s there is a steel screen inside the fuel pressure regulator that can get clogged with debris. Once cleaned out, many see improved mileage.

You mention tires. Have you changed the psi?

 

[Diamond B Ranch]

Sleeper and Dave,
As for the winter thing, I am in North Florida and we run the same fuel year round.
John,
As for the mod syndrome, I also am into Jeeps (Just Empty Every Pocket) so I understand that as well. I will look into the fuel return. The other mods are on the list.

My primary concern is to get the mileage where it should be before I upgrade too much. The plan will be for a improved air intake, chip/program, exhaust and digital gauge/monitor. If there is something amiss, I would like to fix it before I upgrade and possibly exagerate the issue.

Any other thoughts on what would cause the drop off. The automatic has not been rebuilt, but I do not feel any slipping. I don't know if there is something else that could be an issue, like the TC not locking up or something.

 

[bigdiesel99]

you could be sucking air into the the system, there are kits out theere to fix it ITP diesel sells a pre pump filter kit that will help it cost about $110 if you want the better fix and have the money get a FASS or a airdog... this will deffinatly help.. if you were getting 17 before and it got worse with out reason an intake and programmer will not fix it, get back to where you were and then get those things.....

 

[fgtex]

.. if you were getting 17 before and it got worse with out reason an intake and programmer will not fix it, get back to where you were and then get those things.....

Make sure that the hubs are not locked in.

I have only noticed 1 mpg gain with my intake, chip and exhaust.

How you fuel up will make a difference in your mileage from one tank to the next. If I stop at the first click, it is 2 mpg more than if I take 10 mins to fill it up all the way.

 

[Diamond B Ranch]

you could be sucking air into the the system, there are kits out theere to fix it ITP diesel sells a pre pump filter kit that will help it cost about $110 if you want the better fix and have the money get a FASS or a airdog... this will deffinatly help.. if you were getting 17 before and it got worse with out reason an intake and programmer will not fix it, get back to where you were and then get those things.....

This sounds like a very viable option. I will look into it as it is much more financially viable at the time than the regukated return.

My wife fills up the ssame way each time and is good about calculating the mileage the same way each time.

for all the ideas.

 

[whatabudro]

ULSD in combination with new larger tires.