1/0 return ground wire to battery?
 

In my old car, my mechanic buddy suggested that the spot welds on the body of the car may be rusted, and that it would add resistance between the battery in the front and the amp ground in the trunk, so I ran a 1/0 from the amps back to the battery.

My new car won't have that same problem, and I already have the wire, so I am wondering if I should ground the amps in the trunk to the chassis, or use the 1/0 ground wire from the amps to the battery.

Any advantages or disadvantages?
Possible ground loop?

Is your new car "new" or "newer"? If so it will have crappy spot welds, glued together unibody panels and blended metals. You have the wire, it is nice and solid. I would use it. It is not about how big the sheet metal of the car is, it is about the buildup of resistance through all the crappy spot welds and glued together panels.

The new car is an 08. I definitely see your point in the whole composite materials thought.

Ever since I added in the ground wire on my old car, it created a constant volume whine that changed according to the RPMs. It was never there until the wire was added, which is why I'm concerned with a potential ground loop, unless that was something else.

It was drowned out at higher volumes, but low volume listening was not fun.

Grounding the amp to the battery like that wont cause a ground loop unless there is a problem at the signal source. Sometimes installing a new head unit using the factory wiring results in a poor ground. I'm not sure why but it happened in my old car too. I fixed it by running another wire to ground the radio chassis to the battery. That way the amp and head unit are guaranteed to have the same ground potential (voltage).

Personally, I think it would be overkill. A good solid ground will do the trick as long as its in a good spot that power can flow freely.

Run the (-) cable and ground it in the trunk, sometimes you will have noise if you don't ground it...

Having a 'possible' weak ground is underkill?

Run the ground direct and upgrade your battery to body ground and engine to body ground.

I'm a 'firm' believer that all 12vDC +'s and -'s should use the point of contact.

No point in taking chances if the ground is good or bad!

If you are willing to provide a 1/0 path for current to flow then yes, I know I did