Oil leak seem to come from starter. What can it be - main bearing oil seal?

Give more information. What car, what year model? If there is oil where the flywheel is, chances are you have a leaking rear main bearing oil seal or leaking gear box primary shaft oil seal. Coil packs? They should be there to make the car go.

This may be from excessive pressure in the sump from blow-by from the compression process . It is from a blocked PCV valve that is not equalising that pressure. I have also known oil leaks to happen because the rear main bearing cap is leaking oil past the join around the bolts (loose) or no sealing compound used in assembling the rear main bearing.. I would look at the PCV valve as it is the cheapest test first.. Check that the oil is not coming from the front gear box seal or torque converter 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.

Dear Sir,
Here is the oil leaking Problem Identifying Technique

Engine oil leaks from the valve cover gasket are common.

The intake manifold plenum gasket may leak and cause increased oil consumption/burning and a spark knock during acceleration; the gasket should be replaced.

External oil leaks from valve cover gaskets, intake gaskets (front or rear), and the rear crankshaft (rear main) seal area are common. The rear main seal is an unlikely source. Normally, the bearing cap mating surfaces (as well as the sealing surface between the oil pan and bearing cap) are the source for the leaks.

Engine oil leaks at the distributor can be misdiagnosed as leaks from theintake manifold seal, oil pan gasket, or rear crankshaft (rear main) seal. A revised distributor is available if oil is found inside the distributor.

If the oil filter casing shows signs of distortion from excessive oil pressure, theoil pump should be replaced.

Often misdiagnosed as a leaking oil filter gasket, the oil filter adapter can seep from between the adapter and engine block.

Carbon buildup on the top of the piston is common. As the buildup increases with mileage and over time, symptoms may vary from light ticking, to ticking/hammering, to hammering/knocking noises. Fuel injector cleaner often solves the problem.

I think it helps to analyse u r Problem

You don't say what engine it has. The 4-cyl was a better than the V6 for oil leaks.

The V6 had oil leaks from

-rear bank cam cover gasket

-distributor o-ring seal

-oil filter bracket o-ring seal

-crankshaft nose oil seal (less common)

-rear main bearing oil seal (expensive, just leave it)

The 4 cyl leaked oil from

-distributor o-ring seal

-camshaft cover gasket

-rear main bearing seal (expensive, leave it)

The Rear Main Seal is the main area for an Oil Leak on the Transmission Side. You will need to drop the transmission to remove the old rear main seal and install the new one.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

A more common leak is the oil filter adapter,so here is an inspection trick to find your leak.lower or remove the flywheel cover and look at the side of the flywheel that faces forward.Is it dry and slightly rusted or oil soaked?If it's dry the adapter is leaking.If it's wet the oil pan,rear main or oil pressure sender, intake or distributor sealing could be the problem.Use a GM o-ring&gasket if you seal the adapter...better o-ring will last longer.The rear main seal is pretty good on these engines,if it is leaking you may also have a worn rear bearing (or more bearings) which lets the crankshaft vibrate and wobble so that a new seal may still leak.If there are multiple leaks or just a big mess,UV dye and a black light are very useful in pin pointing the worst leak.

no definitely not you probably have a bad rear main oil seal a very common problem on those cars

Hello, this is probaly your rear main seal on the back of your crankshaft. I would check and see if it is a two piece or a one piece main seal. You sound like a knowledable mechanic so this would not be to heard if you have taken a oil pan gasket off a ranger. I have a ranger and did an oil pan in a parking lot without jacking it up and removing the motor and shock like the manual says so I know that takes some skill. So, look up the seal in your Haynes or Chilton Auto Manual and I would replace this seal. Oil near your starter and the back of the oil pan is a classic sign of a rear main seal. Now, to get the seal in out you can refer to your manual and just remember to torque your rear main bearing cap to the proper torque when your done and also try to clean the bottom of your oil sump screen while your down there that would be a benefit later on. A tip to get a stuck seal out is to take an old wire tester the one that looks like an ice pick; this can push out a stuck rear oil seal very easily. I hope this helps your problem and I wish you the best of luck. If you have any other questions just email me ok.

time to take it to the dealer for an estimate only.  Then get the repairs done as you can afford them at a independent garage.  Sadly it may be time for a replacement auto if the rear main seal, or the crank seal is leaking.