Does anyone have experiences with cold-engine tappets sound in relation to oil viscosity?

 

I've been using 5W30 full synth for the last 60k km, and occasionally I do get the tappets clicking (checked them recently with valve cover off and there is no wear), but I can't remember ever hearing them with 5W40 full synth, although then the car was zero to ~60k km old, now it's at ~120k km.

 

I would still like to stay at 5W30, but if with 5W40 the noise goes away for good - I'll get back to that oil. Although when the engine is cold the 5W is the same on 30 or 40, so I don't know, when hot, does the thinner oil escape the lifters or does the thicker oil stay in them - just thinking out loud.

 

Anyone?

 

Thanks.

Does the 5W30 oil meet either VAG 505.01 or 507.00 spec?

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Of course, it is implied by default that we're talking about 505.01 oils for PD engines.

Cold viscosity rises with oil age, so you probably will get some cold valve noise when an oil change is about due on a hydraulic tappet engine.

 

Also, how are you managing to measure tappet wear or drift on one?

Probably a combination of what you suggest about the hot viscosity difference, and internal wear of clearances within the tappet; both leading to increased 'drain out'.  Nice description of the inner workings of them here (clickable pics).

Don't forget the oil in a PD engine does slightly more than just lubricating the cam lobes to open the valves, it also lubricates the injector lobes on the cam, which work under extreme high pressures, so the use of an oil not up to the job is only asking for trouble,

I would do an oil and filter change, refill with the correct spec 5w40 VAG oil and go from there,

note PD150 engines in the VW Golf use to wear cam lobes out

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Cold viscosity rises with oil age, so you probably will get some cold valve noise when an oil change is about due on a hydraulic tappet engine.

 

Also, how are you managing to measure tappet wear or drift on one?

 

Well, the oil is only 6m old with 6-7k km on it - I doubt full synth oil degrades that fast.

 

For the cam and tappet wear, only visual inspection was done to see if the tappets have scores or scratches - which is OK, no wear is visible.

 

Probably a combination of what you suggest about the hot viscosity difference, and internal wear of clearances within the tappet; both leading to increased 'drain out'.  Nice description of the inner workings of them here (clickable pics).

 

Nice explanation of tappets!

 

I would do an oil and filter change, refill with the correct spec 5w40 VAG oil and go from there,
 

 

I just might return back to 5W40 to see if these cold start tappet sound goes away - I've also noticed that the sound doesn't really go away immediately after the engine is warm, I'm supposed to drive for at least 10-20km or 20 minutes for it to go away, but the tappets are heard only when I'm doing really short commutes all day.

My old mkI Octavia used to sound noticeably more"tappety" after 8-9k running fully synth oil.  It was really only when you changed the oil that you noticed the sudden difference.

Prob worth getting your oil pressure checked, could be a bit low.

 

 Well, the oil is only 6m old with 6-7k km on it - I doubt full synth oil degrades that fast.

 

For the cam and tappet wear, only visual inspection was done to see if the tappets have scores or scratches - which is OK, no wear is visible.

 

Cheers. I'm just noticing that you've discussed viscosity and VAG oil codes, but not make of oil. Make honestly does make a difference, like (ok this relates to transmission oils) Sylkolene make transmissions oils that are to the VAG code, but actually give a very notchy shift.

 

And the visual inspection of the cam followers makes sense now.

To reply to myself - going back to 5W40 seems to have gotten rid of the cold start tappets noise. I haven't heard them since my oil change a few Kkm's back and I've done quite a few short commutes.