I switched to synthetic 10W30 last week. I drove 500 miles after that in one freeway trip. I haven't driven the car for the last 4 days. Does that make a difference? Tonight I noticed puddle of fresh oil under the car. This car has never leaked oil before. I read somewhere that after switching to syinthetic the car will leak for a while then stop. Is this true?
I was afraid this might happed with the switch. I haven't had a chance to see where its coming from. I'll look during the day. If its the rear main seal how fast does it leak? How hard is it to replace on a 960 at home? I know i have to drop the transmission. Whats the special tool i need? Can i make the tool myself? This is the first problem i have had in two years of ownership. I guess I was lucky for a while. Thanks for your help.
Justin
94 965 88k

Its not uncommon for a leak to appear (or an existing leak get worse) after changing to synthetic oil. There have been many previous posts on this subject. Regular (non-synthetic) oil tends to deposit a certain amount of gummy "crud" inside the engine and if one of your seals is already worn, this stuff can help plug up a potential leak (at least that is the theory). If your seals are all good, synthetic oil will not cause them to leak.
The first thing you will need to do is find the source of the leak. Could be the drain plug, like NJ960 says. Could also be the filter is not tightened properly. Other common leak points on these cars are the distributor seal (if you have a camshaft mounted distributor), front camshaft, crankshaft and intermediate shaft seals, or the rear seal. The rear seal is going to be the most difficult to replace due to the fact that you have to R&R the transmission to get at it. Before you do anything though, it would be worth your time doing a thorough check and cleaning of the flametrap, oil separator and associated hoses and nipples. If this system is not providing enough vacuum it can cause a seal to leak, or cause a poor seal to leak much worse than it would otherwise.

As to how much the rear seal can leak, could be anything from 1 drop per week to 1 quart per week. Depends on how bad the seal is.

By the way, I changed to Mobil 1 synthetic in my 940 a couple of months ago. Before I did it the car had a very minor leak from the front seals. After I changed to synthetic it has continued to leak at about the same rate (less than 1 qt in 3k miles) but it has certainly not gotten worse.
Good luck.

Kev
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Current: '95 945, 95k miles; '90 BMW 325i, 90k miles. Former Volvos, gone but not forgotten '85 245, 250k miles; '91 744T, 150k miles

If you had the car serviced at a Jiffy Lube, I suggest you return and ask if they used a washer on the drain plug. You should replace the washer each time the plug is removed.

Thanks everybody for all your comments.
NJ960: Good point on the Jiffy Lube places. I learned my lesson with those places a while ago when they lost 2 of 4 screws for the plastic cover under the engine. I do all my own oil changes now. I used a new washer on the drain bolt. That area is clean. The oil filter is clean too.
I'm down 1/8 of a quart from full. Thats about the same as my usual oil consumption. There was no new oil underneath the car today. The only oily spot on the engine is the rear intake cam seal. And thats on the head cover, not below. Its been there for a while. I've never really worried about it before because it was so slight.
The area below the rear main seal as well as the transmission pan look clean. Now im more confused than ever.
Justin
94 965 88K

You may have just been seeing some oil that slopped onto the frame rail while doing the change that took a while to drip off.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel