99 Ford Escort woes

Knock or tap?

A knock sounds like lightly rapping a hammer against the exhaust manifold... a tap sounds like a screwdriver blade against same.

And under WHAT conditions does it knock?

First startup.. aceleration, deceleration? alla time?

If the noise went away the first time with an oil change it might be a stuck lifter. They make additives that might help. An engine that is using twice as much fuel just might be dumping some of that extra fuel in the oil and thinning it out, thus causing noisy lifters or damaged ones plus more. You need to find the source of that fuel consumption first. You don't provide enough information to go on. You don't even state the mileage. The first thing you need to learn is that details are the key to making a diagnosis.

Sorry...the mileage is only 29k. The knocking is almost nonstop, starting maybe 15 minutes or so after startup. Sometimes its more of a softer tap, sometimes its a loud knock. As stated before, the only thing else wrong with it is the fuel consumption. Anything else you need to know?

If it's a knock, not tap, you may have bad bearings, then... and I would hook up a real oil pressure gauge to it.

Smell oil for gas contamination.

I'm surprised there's no other symptoms like rough idle, missing, or hesitation/jerking if there's gas contamination.

One of a few possibilities. The room fuse is blown 10 amp fuse The meter fuse is blown 10 amp fuse The park sense switch is bad The shift lock actuator Or the possibility of a connector that has come undone.