Engine bay + terminal

[oldskewel]

It's 0.67 Amps, not 0.67 mA that you are reading.

You should read the same value (within experimental error) on both the positive and negative cables to the battery. If you are not able to get that, I would get that issue solved before worrying about what the numbers are telling you. Otherwise, you might be chasing theories based on wrong info.

With a 3.0i, the only way measuring up by the engine bay terminal would be helpful is if there is a short in the alternator or starter. Possible - and it does happen (often the very last place someone would think to look when tracing a parasitic drain), but I expect if they exist they'd be higher than the 0.67 A. For the 3.0i (different in this regard vs. the V8s or diesels), the jump port in the engine bay comes from the battery, goes to the starter (where the engine block is used for the ground), and then continues to the alternator, where the cable ends (and the engine block is used for ground).

Cool test you can do with your clamp meter up in the engine bay (for 3.0i) - clamp on the cable coming out of the jump port (going to the starter) and start the car. It should immediately jump to a couple hundred Amps (the starter draw) while the starter spins, then immediately following that, it will probably swing to about 80 A negative as the alternator replenishes the charge the battery just used up. That 80 A should then drop to around 20-30 Amps over the next few seconds as the charge used in starting is restored and the alternator just needs to power the car as it runs.

I would not suspect a bad starter just based only on age. When I had my engine apart a few years ago, I took the starter apart to refurbish it. 186k miles and 17 years old. I replaced the brushes, etc., and they had about 70% of their life left. But my experience on starters in all my cars is that they last forever until you have a problem where the engine won't start (fuel issue, etc.), and then while figuring out that problem, the starter will burn out from all the failed start attempts that cook the windings, brushes, etc.