So is black normal?

 

would a dirty filter affect gas mileage? I ordered a new filter today as my truck has 23K on it and I have never changed or checked my filter, I know, I know...... bad cummins owner.

 

Yes.

But more important, it will affect "Diesel" or "Fuel" mileage even more.


phox

 

You know what I meant. Thanks!

 

Yes, a dirty filter will affect mileage, but not in the way you suspect. If anything, mileage will improve.

 

I beg to differ.

Dirty filter will result in less power,
one tends to floor it more to make up for it,
hence, worse mileage.


phox

 

Hmmmmmm. Then were does the fuel go?

A dirty filter could (potentially) result in less power per a given distance of throttle travel due to filter restriction. Simply stating that more right foot leads to worse mileage is incorrect when talking about filter restriction.

Unless the fuel is hitting the ground and is not going to the injector rail, then mileage should be equal....To a point where the truck wouldn't run.

Now if your talking about mashing your right foot because of restriction, and thus holding it there until 6th (or 5th) gear...Well that's a different story!

-D

 

Feel free to differ.

But the fact is that you can't 'make up for it' by flooring it. As the last poster said, the fuel isn't going anywhere beyond the dirty side of the filter, regardless of throttle position. If it can't get to the engine, it can't get burned. Trying to get more fuel to flow through a restricted filter by 'flooring it' is pointless.

A restricted filter acts as a power reduction device, limiting the amount of power the engine can produce. You will have a difficult time pulling anything with reduced power, but mileage will increase simply because you don't have the power to overcome a lot of aerodynamic drag which is by far the biggest consumer of fuel. You'll have the full amount of torque at low rpm, but not at high.

BTW, that is the only way you'll ever know if you have a restricted filter--lack of power.

 

But there is more than just fuel quanity, there is pressure and timing. Put your foot in it and you'll get longer injection durations but with less fuel flow. I'm not a combustion expert, but I could see this impacting more than total power output.

 

Nope. Pressure and timing are not affected. Only the quantity of fuel injected is affected, and it's just as if you put a stop under the accelerator pedal. As the filter gets more and more restricted, it's as if the block gets thicker and thicker. Finally, all it will do is idle. Then, nothing, if you let it go that far.