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Discussion Starter · #1 ·
I was wondering if anyone has had experience with an issue similar to this:

Typically after hard acceleration/driving, and once in a while during regular driving or idling, I can smell buring oil. It does not seem to me like "blow by", because the engine revs and redlines flawlessly (or it at least seems to). This leads me to think I have a leak out of a gasket, or somewhere else, possibly dripping onto the exterior of the engine, but I can't see any evidence of this.

I picked the car up used a few months ago (currently has 107K), and this seems to have started in the last several weeks. It has had regular maintenance. The previous owner used regular 5W30. I decided to put in Mobil 1 Synthetic 5W30 on the one and only change I have performed. I have added approximately 1/2 quart over the last 3,000 miles.

Any ideas or suggestions on a proper diagnostic strategy? Is the switch to synthetic oil after years of regular oil a bad idea?
 

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synthetic is a good choose to switch to at any time. You might have a bad value cover gasket leaking in the back where you might not see it or leaking past the plug seals both very common. Also I remember reading a Car&Drive long trim test on a 90's M3. When new they where adding a qt every 5k
 

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Discussion Starter · #3 ·
I'm starting to think it is the valve cover gasket too, because although I smell the burning oil, the exhaust is not clear and normal. Anybody have any idea on cost? Is this a relatively easy DIY?
 

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Humble E34 lover
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Thanks for the info. I found out the head gasket may also need to be replaced, so I am evaluating my options
What makes you think head gasket may need to be replaced?
 

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Disagree strongly on switching to synthetic after years of dinosaur goo. It makes everything leak. For more detail, search similar posts.
 

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Discussion Starter · #8 ·
Jason,
I read the oil threads. With the exception of a quote from the valvoline website that switching back and forth is OK, the posts sounded convncing that I shouldn't have swithed to synthetic with 107K.

I now have a leaking valve cover gasket and possible head gasket - although I'm not sure this is what caused them.

Should I switch back to reg.? Or step up to a thicker syn? If I caused damage with the synthetic, is it reversible?
 

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Don't ask me, I'm a sofa.
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Both.
- There's no doubting the leak problem lies with the gasket.
- But IMO, the leaking will likely be brought on by the switch, where it was coping under your mineral oil.

Switching back will not help the gasket, now that the "seal's been broken". You also need to keep an eye out for other leaks appearing, also suddenly burning excess oil (blow-by from ring wear).
 

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Turn Burglar
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M cars burn oil, it's ok. When I worked for BMW, the official answer to "My M_ is burning oil! What should I do?" was for me to say "That's normal and perfectly fine. Keep your oil level within factory parameters and dont worry about it. If your M_ stops burning oil, then you need to worry."
Anyway, mine consumes a little too when I drive it. It's nothing to panic about. Try switching oils and see what works well for you. I've found that my car burns a lot of Rotella T Synthetic 5-40 (winter oil), but it burns less Mobil 1 15-50 (summer oil).
 

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Discussion Starter · #13 ·
Turns out it is both the head gasket, and valve cover gasket, and not simply a little oil consumption. The shop guy showed me where oil has been leaking all over my block.

I'm planning on having an indy shop do the work, to the tune of around $2400. Dealer quotes were closer to $3000. Any input on other parts that are "musts" to replace while I have the engine apart?

BTW - for what its worth, my mechanic was adamant that switching to synthetic oil did not cause the gasket to leak. He said it had likely already been leaking, and the finer synthetic oil simply leaks faster. Either way, he said the gaskets would have need to been replaced in the near future.
 

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Synthetic oil can cause leaks. This is because they tend to "wash" away the goo that had been stopping the leak in the first place. Now witch would you rather have a goo filled engine with no leaks or a clean one that has to have a few gaskets fix that where bad to start with.

A car dose not have to over heat, blow a cloud of smoke, have water in the oil, run bad, miss, ect... to have a bad head gasket! They can blow so they leak externally, just oil,just water, or both. Have had it happen to me.
 

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Turn Burglar
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Synthetic oil can cause leaks. This is because they tend to "wash" away the goo that had been stopping the leak in the first place. Now witch would you rather have a goo filled engine with no leaks or a clean one that has to have a few gaskets fix that where bad to start with.

A car dose not have to over heat, blow a cloud of smoke, have water in the oil, run bad, miss, ect... to have a bad head gasket! They can blow so they leak externally, just oil,just water, or both. Have had it happen to me.
That's a very common misconception. Synthetic oil does not cause leaks in your engine, but if there is a leak in your engine synthetic oil will find it.
 

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Discussion Starter · #19 ·
No, the car does not run rough or overheat. It does occasionaly stumble and drop below idle revs when I stab the clutch to slow down. Revs occasionally fluctuate slightly when idleing, but neither one of these seems abnormal to me for an M car, I am not sure it is the head gasket, but the shop seemed convincing in their diagnosis. I just went and bought compression testing equipment to do today. If I am not losing compression, I figure I can at least wait out replacing the gasket, if it is indeed bad. I am also planning on cleaning out the engine bay to better see wherethe leak is coming from, and may try switching to a more viscous oil.
Should I try switching back to a conventional or "high Mileage" (Valvoline Max Life) oil, or just a thicker synthetic?
 

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I would hold off on the headgasket as doesnt sound blown to me!!

Any mayonnaise (white/yellow goo) on dipstick or oil cap?

1/2 quart in 3k miles does not sound too much to me at all, especially if you have been giving it some beans!!
 
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