The 2005 honda pilot appears to have a rear main seal leak

black oil or red oil
if red it is a torque converter seal and the transmission will have to be removed
use a professional auto transmission specialist shop
black oil is sump oil and can be from a rear main seal or leaking from a rocker cover gasket and running down to under the bell housing making it appear as a rear main seal

Try running some of that high-mileage engine oil next time you do an oil change (it helps to swell engine seals slightly). If the problem clears up or is reduced, then it's likely that the rear main oil seal is starting to leak a little. The rubber seals will harden up and shrink a little with age.
I would also powerwash the entire area clean, so that way any leak will be easier to monitor and pinpoint.

If it's oil, it's coming from the rear main seal.. I would go with this idea.

The seal doesn't cost much but the labor to get to it does.

To give you an idea what is involved the procedure is illustrated below from the service manual:

Removal & Installation 3.8L Engine To Remove:

1. Drain the engine coolant.
2. Drain the engine oil.
3. Remove the oil pan.
4. Remove the engine flywheel.
5. Remove the rear oil seal housing and gasket. Rear seal removal 3.8L
   
   
6. Remove the rear main seal by placing the housing face down on 2 blocks of wood. Using a drift tool and hammer tap the seal out of the housing.

To Install:
NOTE: Do not lubricate the rear main oil seal or the installation tool. Do not touch the sealing lip of the rear main seal once the protective sleeve is removed.
NOTE: Use a clean lint free cloth to clean the crankshaft sealing surface. Remove sharp edges or burrs that could damage the rear main oil seal. Remove burrs or sharp edges with a crocus cloth.

1. Carefully remove the rear oil seal from the protective sleeve.
2. Install the oil seal onto the seal driver EN-47623 or equivalent by placing the seal at an angle and twisting until it is fully seated.
3. Install the seal into the housing using the seal driver EN-47623 or equivalent and driver handle J-8092 or equivalent. Apply downward force until the seal is seated. NOTE: Ensure that the housing gasket is installed correctly and that the oil passages are not blocked.
   
4. Using a new gasket Install the rear oil seal housing on the engine being careful not damage the rear main seal. NOTE: The plastic inserts are used in production and are not needed for assembly.
   
5. Hand tighten the bolts. Rear seal housing alignment 3.8L
   
   
6. Place a straight edge on the crankshaft rear oil seal housing flange and the engine block oil pan flange. Using a feeler gauge check that there is no more than .0004 in (0.10 mm) step on each side. Rotate the housing to make the steps equal on both sides.
7. Tighten the housing bolts 11 ft-lb (15 Nm) plus an additional 50 degrees.
8. Ensure that the housing did not move out of specification. Repeat step 6 if the oil seal housing is not within the specified range. Replace the rear oil seal housing if the specified measurement can not be reached.
9. Install the flywheel.
10. Install the oil pan.
11. Fill the engine oil and the cooling system.
12. Check for leaks

5.3L Engine To Remove:

1. Remove the flywheel from the crankshaft.
2. Remove and discard the crankshaft rear oil seal from the rear cover.

To Install:

1. Use clean engine oil to lubricate the outside diameter of the crankshaft rear oil seal and rear cover oil seal bore.
2. Install the tapered cone and bolts of a J 41479 or equivalent crankshaft rear oil seal installer onto the crankshaft.
3. Place the crankshaft rear oil seal onto the tapered cone.
4. Install the threaded rod of the J 41479 crankshaft rear oil seal installer into the tapered cone. Rear main seal installer 5.3L
   
   
5. Install the crankshaft rear oil seal by turning the handle of the J 41479 clockwise.
6. Remove the J 41479 crankshaft rear oil seal installer from the crankshaft.
7. Install the flywheel onto the crankshaft.

--- I'm not sure what the exact cost would be as the hours were not listed for this procedure on my online resource.

OIL LEAKS UNDER CAR COULD BE COMING FROM LEAKING OIL FILTER OR OIL PAN GASKET.CHECK FOR OIL LEAKS AROUND REAR MAIN OIL SEAL AND FRONT TIMING COVER CRANKSHAFT SEAL LEAKING OR LIP SEAL AT THE LOWER TIMING COVER TO OIL PAN.

First have to determine where are you loosing it from.
Possible engine oil leak areas : Valve cover gasket,oil pan gasket, rear main,oil filter. crank or cam shaft seal, oil pump. Pcv valve.
If its transmission oil leaking here are a few areas of interest: shell of transmission( depending where on the shell could be oil pump, or converter., vents, and axle seals.
If your not capable to jack the vehicle up and look for the leak , then take it to a repair shop.
Keep me posted

OIL IS LEAKING BY VALVE GUIDES.BURNING WITH FUEL OR REAR MAIN SEAL LEAKING. CHECK AROUND FLYWHEEL AREA TO THE OIL PAN .ALSO IF FRONT CRANK TIMING COVER SEAL LEAKS IT WILL LEAK WILL CAR IN MOTION.OIL WILL LEAK ALONG THE HIGH WAY YOU WILL LOSE OIL THAT WAY.

could be valve seal in engine vehicle still under warranty take to dealership and have it replaced.

First, do you see oil leaking on your driveway? Have you looked under the car and checked to see if any oil is dripping?A rear main seal will drip down the front cover plate of the transmission sometimes from the inside, appearing like a front seal leak on your transmission but the oil will not be red fluid you would expect if that were the case. I would not worry about rear main unless you see a leak there. Look your entire engine over and check for leaks everywhere. Several small leaks can add up to an overall large oil loss. Correct the larger ones first.
Generally all seals will last far longer if you change your oil frequently using a good quality lubricant. If you are loosing some oil, use one of the oils made for high mile engines. I suggest you use a mild additive like marvel oil 1pint with every oil change...it removes sludge, carbon and varnish buildup without the drawback of knocking it loose all at once, where it could plug up your oil pump screen. (it also smells good) Change oil every 3000 miles for the first three or four intervals, then consider using a good synthetic oil. Synthetics far outperform any other lubricant in every area! Avoid overheating your engine...overheating does more damage to seals than any single other item...When seals get very hot they harden up, crack and fail.
Good luck with your car!!!

hi from uk if your oil ? leak is from rear of engine area ? but you say oil level in engine is ok? and not needed to top up ? then i would check the gearbox/transmission oil level? for any loss? asap it may be your leak is coming from g/box/transmission front seal ? but either way gearbox will have to come out do be able to replace both rear engine crank seal and g/box front seal at the same time ? hope this helps you don;t delay in topping oil level in trans ?

Its clearly that you got oil leak...
here is a solution for you:
Could be your rear main seal...how many miles are on the vehicle? Sounds about right for a 10 year old car if you drive it a lot and the price sounds about right to fix it. Actually, it's a bit cheap as they have to pull the engine to replace it...usually...if they do it right, they do.