Synthetic oil myths part II - it causes leaks

[big x]

I thought I'd test this claim out on my 120k BMW 740i V8 M60 an engine known for oil leaks and bore wear.
I refilled with a mix of Mobil 1 10W40 and Mobil 1 15W50 both fully synthetic blended to be close to Castrol GTX 15W40 high mileage mineral oil.
Four leaks started almost straight away,both sides of the cam covers dripping straight onto the exhaust down pipes...very noticeable.Left side of the oil sump and a slight weep from the crankshaft pully seal.The inside of the V underneath the intake manifold also started to fill with oil which over time will work it's way into the rear spark plugs holes.Over night perhaps 4 or 5 seperate patches will be left on my drive.
After 500 miles I refilled with Castrol and all leaks have stopped.I also noticed that slight tapping you typically get with hydraulic tappets and synthetic oil when first started went away.I changed again after 500 miles with the saved Mobil and the leaks started again.

On my 100k C180 97 I have been using fully synthetic.It has the common oil weep on the front left of the head gasket where the timing chain runs however the undertray catches it so it's of no concern.With mineral oil the seep is slightly less.The use of synthetic in this application clearly outweighs the leak.

Conclusion....on higher mileage cars synthetic oil will find out any older gaskets and may leak even if it is the same viscosity as mineral oil. There are plenty of threads on the US BMW forums to back up my findings.

adam

 

[Dieselman]

So fix the leaks. The leaks are a result of the synthetic oil cleaning out the gunge stuck in the seals.

If the engine had been run on better oil and flushed every now and then it probably wouldn't have the build up in the first place.

I hate leaky engines.

 

[big x]

So fix the leaks. The leaks are a result of the synthetic oil cleaning out the gunge stuck in the seals.

If the engine had been run on better oil and flushed every now and then it probably wouldn't have the build up in the first place.

I hate leaky engines.

The golden rule with running bangers(the cars worth circa £800) is to spend as little as possible.It's cheaper to change the oil type rather than spending time and money on gaskets and seals on a complex V8 !

adam

 

[Dieselman]

The golden rule with running bangers(the cars worth circa £800) is to spend as little as possible.It's cheaper to change the oil type rather than spending time and money on gaskets and seals on a complex V8 !

adam

Hmm. Even on old cars I have still changed gaskets and seals to stop leaks. The parts cost next to nothing and the result is very rewarding.

 

[big x]

Hmm. Even on old cars I have still changed gaskets and seals to stop leaks. The parts cost next to nothing and the result is very rewarding.

My last BMW an E28 (the old shark nose one) I bought with 140k up and kept for 10 years before the sills and jacking points rusted out and it went to car heaven.It did 280k on mineral oil and the engine was never touched.The point being the rest of the car wore out first.On modern cars most of which should have longer lived bodies synthetic makes sense for sure.I was amazed those Impreza guys with turbos weren't using fully synthetic.
One major cause of leaks on the BMW E32/34 is people putting the wrong type of hydraulic fluid in the brake/steering booster system.CHF11s is the correct stuff a green fully synthetic oil which is only £6.50 a litre from ECP.Even though it says that on the resevoir I've seen so called specialists

put ATF in which is a different and will leak!

adam

 

[stever]

I have a 1979 w123 280CE running on Comma 10W/40 fully synthetic (MB spec), and no leaks. It also burns very little, maybe 150ml/ 1000 miles at most. Mileage is 143k.