Oil analysis

[Fred W]

On a carbureted engine changing the air filter *does* result in better fuel economy. Thats where the old convention came from. But it no longer applies to a fuel injected engine, even your diesel.

As for reduced performance being caused by a restrictive filter, the throttle plates are by far the greatest restriction to intake air flow in anything short of wide open throttle. So, yes, at WOT a restrictive or dirty filter will cause the engine to be somewhat restricted in air flow. Unless you are at the drag strip, how much time is your throttle actually pinned wide open; how important is it to get those extra couple of horsepower at WOT? Most of us would be better served by pushing back from the dinner table more often to improve our power to weight ratios.

 

[Redfish Hunter]

Fred, I am extremely bothered by your unwillingness to address the real issue here. Will a K&N filter increase my...size?

I semi-disagree with you about the carbureted engine's fuel economy suffering. Does the fuel not still follow the air? If the air flow is not there, the fuel will not flow more than the air flow can pull can it? I can see a loss of power... but as far as the fuel flow, to the carburetor wouldn't a dirty air filter be just like not opening the throttle fully? Be patient with me here, I am asking not arguing.

My diesel does not have a throttle plate so it sort of throws the discussion in a different direction.

And I PROMISE I am not being contrary and arguing with you but... I have seen a very dirty air filter "release" some of its dirt into a Cummins diesel. The turbo was doing what it does and the clogged filter was the weakest point in the system. The truck was brought in for service because it was running very badly. My cousin (the owner) graciously allowed the shop to put his crushed and sucked in air filter on display as a What Not To Do on their counter.

But I do agree with you that a dirty air filter usually keeps its dirt.