[lateapex911]

Originally Posted by Jeff Higgins

Engines simply do not lose horsepower over the years. Not unless there is actual damage causing that loss. Normal wear and tear does not lead to a loss of power. If the rings are shot and it has no compression, if a lobe or several are wiped flat on the camshaft, then you will see a loss of power. If it "runs well" (as you state) and has no such clear mechanical issues, it has not lost power.

If properly cared for, 146k is about halfway (or a bit more) of the service life of the 3.0 liter motor. They commonly exceed 200k miles by a good deal, many of them reaching 300k before a rebuild is required. Yes, they have issues with broken head studs, and that would be an expensive fix, but it does not require a full rebuild. Yes, they do leak oil from a number of places, but those repairs are well documented here and elsewhere, and likewise do not require a full rebuild. As a matter of fact, most of those repairs can be affected with the engine still in the car (the notable exception being the "triangle of death", to which your CIS effectively blocks access).

So, no, you will not notice any improved performance after a rebuild. That is not how this works if the engine is in good running order prior to the rebuild. Performance upgrades are another matter entirely but, again, a stock rebuild will gain you nothing.

So, at this point, simply repair the oil leaks and keep having fun driving your car. You have a wonderfully robust example of the 911 (some say the 3.0 is the most robust overall) that has many, many happy miles left in it. Just enjoy it. And, for now, save a ton of money that wouldn't buy you a thing.

So, his OP stated he was burning oil, if so that suggests that he's either got worn rings, or valve guides. If the valves are seating well, yes, he's fine. Worn rings will cause loss of compression and some power.

Is it noticeable?
Hard to say, but probably not. (One because it's probably slight and two, because it's been slow in happening.

Glad to read your comments about the 3.0 and it's longevity, I'm far from an expert but I was going to mention that the 3.0s are among Porsches stoutest engines.