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My friend has an 04 sxt with an r/t head and internals and a built block with rods JE pistons, the works. We did his oil change with synthetic mobil oil and after 1300 miles we had to ad 2 qrts because it was dry. any ideas?

Some cars will do that. I can't remember why (maybe there isn't a for sure reason...), but change it back to either dino or semi-syn and see what happens if it keeps it up.

How many miles were on the rebuild when the synthetic was put in?

Synthetic oil has much smaller molecules, so it will get past places the conventional oil won't go. If the rings aren't fully seated, or there is still a good crosshatch on the cylinder walls, the synthetic will get into those tiny grooves better than conventional oil, and be burnt in the combustion process. I would not recommend synthetic until at least 6 to 10 thousand miles just be be positively sure everything has mated well. Even normal oil is much better than it was 20 years ago, so it may take a bit longer for a rebuild to break in. Especially if the rings are of a harder material than the standard cast iron rings.

Yeah, at first I was thinking it was a rebuild, but then it never really said it was rebuilt recently so I changed my reply.

+1 to the above if it was in fact, just rebuilt.

As already mentioned, DO NOT use synthetic on a rebuilt motor until the motor is broken in. Synthetic oil are so good that a rebuilt motor will not properly break in if using synthetic oil.
Get some basic 5-30w oil in it and drive it for 1500 miles of course keeping an eye on the oil level as during break in it will consume some oil while everything is seating. At 3K change the oil again then push the interval 3K so your changing it at 6K. At this time it should be ready to switch over to synthetic.
Most modern engines will go almost 10K miles before breaking in properly....

the motor had 40k before building the block and swaping the head. it has been 6k since since the built. We have been using synthetic every since. Today, I was driving behind him and i noticed that every time he would punch it a lil he would let out black smoke. The motor has no leaks, everything is in perfect working order. We will try the regular oil 5w30 and see what happens. any more input?

Black smoke is generally from the engine running rich. If that's the case, I'd be concerned with fuel being dumped into the oil. Perhaps it is from a poor tune? Maybe a leakdown test should be done as well just to check the internals. Perhaps I'm playing devil's advocate with all of the above, but if some simple checks can save a bigger problem later...

^^^
He's correct,
Black Smoke = too ruch
Blue Smoke = oil burn
White smoke = coolant burn
You may actually be running rich enough to where you could be washing the cylinders down with excessive fuel and contanimating the oil thining it with raw fuel which inturn could get sucked into the pcv system easier and right into the intake manifold...
Drain the oil and put in some Walmart SuperTec 5-30, it's cheap oil by the price but it's a relabeled name brand oil so your not buying junk either. In the meantime find out what the fuel richness problem is.....

Try different oil. With Mobil 1, I had a quart per 1000 miles disappearing on me with a very healthy engine. I switched to Castrol Syntec and had less than one quart gone in 5000 miles.

An engine will break in with synthetic oil, it will just take longer.

Also, it only takes a couple thousand miles to break in an engine.

yea you are right, we did noticed the oil to be very thin and watery, not over filled but very liquity. I guess the fuel might be mixing. thank you for the information guys, i'll keep you posted

unleashedcc wrote: he would let out black smoke.
.
.
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everything is in perfect working order.

apparently not.

haha...............not obviously, i meant leaks or any other common problem

This info is going to be unrelated to his certain situation but after a customer complaint at work yesterday about his 2007 Jeep consuming 2quarts of oil in 3000miles I learned something new:
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NORMAL OIL CONSUMPTION:
Below are industry standards for normal engine oil consumption:
Mileage below 50,000: Normal oil consumption is one quart for each 1,000 miles driven.
Mileage above 50,000: Normal oil consumption is one quart for each 750 miles driven.

TEST TO DETERMINE ENGINE OIL CONSUMPTION:
Operate engine to normal operating temperature. Fill engine oil precisely to FULL mark on dip stick gauge. Use paint pen to mark the engine oil drain plug to prevent tampering. Check engine oil level after 1.000 miles driven. Refer to normal engine oil consumption listed above.

POSSIBLE CAUSES FOR EXCESSIVE ENGINE OIL CONSUMPTION:
PCV OR CCV SYSTEM: Check the crankcase ventilation system for proper operation. Oil may accumulate in the throttle body or intake manifold. Also, rocker arm lubrication oil flow returns to oil pan through drainback holes in top of cylinder head. Plugged or restricted oil drainback holes may contribute to excessive oil in crankcase ventilation system.
SPARK PLUGS: Examine all spark plugs to identify the affected cylinder(s). Spark plug on the affected cylinder(s) will usually be fouled or wet with engine oil.
VALVE GUIDES AND VALVE STEM SEALS: Inspect valve guides on the affected cylinder(s). Replace valve stem seals on the affected cylinder(s).
PISTON RINGS: Check piston rings on the affected cylinder(s). Piston rings may be too tight / worn / broken / carbon build up in the oil control ring.
CYLINDER WALL: Examine the cylinder wall on the affected cylinder(s). Cylinder wall may be severely scuffed. Perform hone procedure on the cylinder wall or replace cylinder block / short engine assembly as required.
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Never knew an engine would consume that much

Those have got to be Dodge's "industry standards." I don't ever recall seeing anything that crazy. One quart every 750 miles, even 1,000, is ridiculous and completely excessive. That would mean in a Neon, before a 5,000 mile oil change, you will have already changed the oil completely at 4,500 miles and then some at 5,000. Very poor standards from Dodge in regards to their own engines.