knklhead

Hi.

My 2004 525i with 95000 runs perfectly and in great, almost new, shape! I took advantage of a Mobil One rebate offer for the oil. The very next business trip I averaged 33.6 MPG! I was ecstatic. This at probably an average of 75 MPH.

Fast forward a few weeks, and I noticed a burning oil smell. I raised the hood and saw some smoke hovering around the manifold on the engine's right side, back. I used a mirror and it appears as if a small bit of oil was settling on the chrome "wings" that extend from the side of the engine and dripping on the exhaust manifold. I wiped it off, thinking I may have spilled, but it comes back each time I drive the car. I check the oil levels each time I drive the car and it seems as if there's not a lot of loss, but keeping an eye on it.

I contacted Mobil (800 ASK MOBIL) and was very surprised by the nice guy I talked to, Tyler. He was honest, indicated that yes, indeed, Mobil One could cause a "pinhole" leak in a valve cover gasket in a car with higher mileage. He suggested running Mobil Super High Mileage for three or so oil changes, THEN run Mobil One again. I explained why this wasn't a viable option, and that I'd expect Mobil to do more for me. He suggested that Mobil will do everything it needs to do to satisfy a customer complaint, and he will have his supervisor contact me to get the ball rolling to identify the problem and do an oil analysys, etc. Tyler was extremely nice.

Because of my first interaction with Tyler, I am looking forward to a resolution that will save me from an expensive gasket change simply because I took a shot to start using "recommended" Mobil 1 0W-40. If they continue to be as pleasant as they are now to deal with, I am optimistic that we simply need to do a better job of spreading the word, in a professional manner, that if considering Mobil One synthetic, here is the way to prep, what to expect, etc., etc.

I did not have to put words into Tyler's mouth that Synthetic at higher mileage can cause gasket issues. Has anyone else had synthetic problems or gone down this route with Mobil before? I am cautiously optimistic that Mobil is going to stand behind their products and their guarantee about being safe for your engine.

Stay tuned.

BimmerFan52

What oil were you using previously?

KyleB

I've always used 5w30 Castrol straight from the dealer and my 530i returns right at 30 to 30.5mpg on the interstate. BMW switched oil suppliers to Shell, and I plan on using the new OEM oil when I change the oil in two weeks.

Yes, I think most of us have heard stories of car owners switching oil types/viscosities which induced oil leaks. I think that oil you chose is simply way too thin, and I'd be surprised if Mobil does anything for you considering the age and mileage on the car.

I'd change the valve cover gasket and go back to putting the correct weight oil in the car, the heck with any sales or rebates.

twh

Been running Mobil 1 0W-40 since off warranty on both the 2006 E60 and 2009 X5. Never had a problem. I don't think this guy is right that Mobil 1 can cause a pin hole leak in a gasket. Doesn't make sense.

You might go surf over at bobistheoilguy.com. There is bound to be stuff there if it's true.

BimmerFan52

I'm sort of scratching my head.

The title of the thread is 0W-30, but the first sentence in the fourth paragraph sounds like he used 0W-40, and the fifth paragraph sounds like he is just now trying synthetic in the engine.

KyleB - What is your point regarding the "thinness" of the oil? I don't know what he was running before, but I would think the gasket swell characteristics would have a bigger potential effect on causing a leak than the kinematic viscosity of the oil at 100C.

knklhead

My mistake, and I edited the subject. Thank you for catching, I made a typo! I DID just now try synthetic, and it was the recommended 0W-40 and that's exactly when the valve cover started to leak.

seanjordan20

+1

I would have to agree about the gasket swell characteristics would be the main cause. The car has 95k on it and the valve cover gasket has not been changed before. We all know that BMWs leak. The thinner oil just found its way out versus if he stayed with the heavier weight it would have happened later down the road. I would say switch back to the heavier weight and see what that does. Eventually you will have to change the gasket anyway you are approaching 100k. I had mine done around 65k because of a leak using OEM oil.

knklhead

I have read "Bob's the Oil Guy" posts and he's very knowledgeable, but here are the facts so far.

I have had the car for three years, and prior to me changing the oil it was done at various locations -- I assume Castrol, since that's printed on the filler cap.

No leak whatsoever, but when I changed the oil and filter myself, I used 0W-40, and then there was a leak. My bet is this is the very first time Mobil synthetic was used on this car.

Tyler at Mobil last night mentioned (I hate to say "admitted" because that would sound like someone pinned him down! -- and they apparently tape their calls) that Mobil One Synthetic CAN cause valve cover gasket leaks AND he even mentioned rear seal leaks. Read that again if you have problems with the concept. I felt as though it was caused by 0W-40 syn and he confirmed it.

More proof, he suggested that my car "wasn't ready" for 0w-40 Syn, suggested I do three oil changes of Super High Mileage 5W-30 to prepare gaskets and THEN use 0W-40 syn, which I would now not take another chance with.

Now, so far, all signals point to Mobil helping me with diagnosing/confirming leak and doing an oil test, etc -- as well as covering the cost of gasket replacement. So far I am optimistic they will do the right thing.

RIHI

I think you are reading way too much into what Tyler is "admitting to". Being a Mobil dealer in the 80s and 90s, and having used Mobil 1 in quite a bit of oil changes and having the "now it leaks" problem when a thinner oil is used, not because the oil caused a pinhole but the old gasket is not as pliable as new and cannot contain the thinner oil. This is normal for higher mileage cars. Either change the VCG or go to a thicker oil.

BimmerFan52

There is nothing "thinner" about Mobil 1 0W-40. The "0W" in the oil multi-viscosity grade is known as the "cold cranking viscosity", and is an indicator of the force required to rotate an engine at a low temperature to simulate starter torque and battery power required, as well as the "cold pumpability" or force required to pump the thick oil through small orifices (simulates the oils ability to begin lubricating upon startup). It has nothing to do with the viscosity of the oil at operating temperature.

The "40" in the number is the oil industry's range representation of the kinematic viscosity of the oil (ability of oil to flow) at 100 degrees centigrade, and can be an indicator of the oil's ability to maintain a hydrodynamic film (a film that actually separates moving metal parts) at important points in the engine such as journal bearings. If the oil's viscosity is too low the film can collapse at high temperatures under high forces (engine making maximum power) and metal will wear against metal.

Mobil 1 0W-40 is known as a "light" 40 grade, as it is at the lower end of the range of kinematic viscosity that the industry uses to call the oil a 40 grade. Castrol 5W-30 synthetic falls in the upper end of the 30 grade range so the two oils are very similar in viscosity at operating temperature even though one is a 30 grade and the other a 40 grade.

While there are some documented cases of switching from Dino oil to synthetic causing leaks, in this case some caution used in declaring cause from correlation as the car does have 95,000 miles on the engine.

But assuming the leak was because of the switch to synthetic oil, the very uniform molecular size of man-made synthetic oil as compared to large and small molecules in Dino oil, the possible difference in gasket swell characteristics of the oils and the somewhat superior cleaning action of synthetic all could have contributed to the leak.

Without knowing the previous history of oil used and the drain intervals, declaring that the leak was caused by the switch and if so what characteristic of the synthetic oil caused the leak is likely impossible.