4.8iS w/cold start top end noise after oil change
 

My 06 4.8iS has 55k on it and I just had a dealer oil change under my 100k pre paid maintenance contract.

It now is noisy on cold starts. Last 3-5 mins on idle or goes much quicker if I drive (1-2 mins) Cannot be heard inside car.

I have read all of the posts regarding VANOS and timing chain tensioner but what I am confused about is why it will now make this noise on cold start and it did not pre oil change.

I have a sneaking suspicion the dealer is NOT using the right oil and perhaps we have a NA oil with a lower HTHS. Of course, dealer will only say its BMW approved oil.

At 55k, I should not need a timing chain tensioner but it is a quick , easy and relatively cheap fix and if its not the issue, its not a bad thing to do. Perhaps the oil change left the tensioner not fully filled as it is a hydraulic device.

Your input and experience appreciated

David

You have an engine noise that you can't hear inside the vehicle, and which goes away in a minute or so if you drive the vehicle, as recommended. First thing is to stop idling it on a cold start.

The BMW dealer doesn't likely stock anything but the correct oil. Also, the fresh oil will have a different (correct) viscosity than the old oil that was drained out.

Doesn't sound like much of a problem.

Thanks JCL,

We have talked before regarding oil quality and specifically HTHS. VW recently reconfirmed they needed 3.5 min (HTHS 150) as they have trouble with valve train and particular durability and noise with 'hydraulic' components of the variable valve timing namely the 'sequencer'. In short, standard NA API or ILSAC oils with a typical 2.9 HTHS or even lower are not acceptable. As far as I know, BMW spec calls for 3.5 min.

If the older oil was no longer in spec, its likely it was thinner , not thicker hence I would expect less noise from a new oil in spec than an old oil, given it was the same grade.

I have the luxury of a full lab at work where we can run KV100, KV40 , CCS and HTHS 150.

I think I will pull a small sample and in the interests of completeness, do a basic analysis.

Not sure why all the focus on HTHS, if the only noise you hear is for the first minute when the engine and oil are both cold. Wouldn't you care more about the viscosity? Check the viscosity at 40 C and see what it is.

My comment on old vs new oil was based on my expectation that the viscosity improvers will change (be depleted) over time.

VW is now recommending up to 50,000 km oil change intervals, so I see why they may care more about HTHS specs.

Well, we could talk at length but not all VI's will suffer the same permanent shear loss under high shear conditions. Also, as I am sure you know, full synthetic base stocks typically have higher inherent VI hence less VI Improver is required. That leads to the typical observation that there is less loss of initial viscosity in a fluid that has less VI to start with.

You are however correct that a quick KV40 will answer a lot of questions. And to be clear, the reason I am focusing on this is the change pre and post oil change.

Its always good to have these discussions with someone with so much experience.

David

I get some lifter noise on cold start-up, especially when it is below 10-15degC
Lasts for a minute or less, but normally I am driving it by then anyway. Seems pretty normal to me. I had similar noise in my Audi 4.2L V8 - S4.

I don't get it, why sould I not idle it till temp goes out at least blue mark? driving it with cold oil supposed to be bad?

When the engine is cold, there is a higher wear rate. Engines warm up very slowly without some load on them, so idling an engine just extends the warm-up period. Extensive testing by all engine manufacturers has shown that the least amount of engine wear occurs when you start the engine, wait a few seconds until you have oil pressure, and then proceed to drive it gently. Don't rev it up or apply large loads, but do drive it. That shortens the warm-up cycle, and reduces the engine wear. Essentially, the duration of the warm-up cycle is more critical than whether or not there is load applied. If you see your owner's manual, it says this.

The above assumes that you have visibility through the windscreen, ie that it is safe to drive.

I love it!

OT but...Just yesterday I saw a lazy guy driving his minivan down the residential street with the windshield sun cover still on but slightly folded enough to be able to see. Laziness or stupidity, you decide.

All of the above.