Over the last 50.000km, my classic SAAB 900 turbo 16
had developed lifter tick. First on startup only, then also in idle when the oil was not steaming hot. 600km long distance on the Autobahn, and the hydraulic tappets were silent. Then drive 15 minutes through town, and they'll start to clatter. Or blast up a mountain pass and stop on the summit - peferct, silent idle. Now cruise downhill, and in the valley there will be noise...
At km 534000 I had the transmision rebuilt. That is, I had a transmission frankensteined - with parts from three different gearboxes, including my original one, as new parts were nearly unobtainable. In this process, the gearbox housing, which doubles as the oil pan for the engine, was changed as well. I think the sump of this "new" gearbox housing may not have been spotlessly clean, and that some crud came loose and now blocks some oil passage to at least one of the hydros. For lack of time to take care of the issue properly, at 600,000km
I chose to try a thinner oil and switched to Shell Helix Ultra 0w-30 (had been running 0w-40 for the last 190.000 before that). ( Here
is a link to the last UAO discussed on BITOG.)
And it worked: the hydraulic tappets are now quiet. There is some clatter at start-up, but it quickly fades away and after a few seconds the engine is completely silent again.
But how does it wear now with the ultra thin oil?
I was not afraid for the bearings - the manual specifies 10w-30 and 10w-40, and given how bad early VII were and that early multigrades often had HTHS as low as 3.1, I assumed that the Shell AV-L should do fine. After all, as an ACEA C3 oil, it must have a HTHS of at least 3.5...
I was not so sure about the valve train (DOHC with flat tappets,, hydraulic elements and timing chain).
Well, here's the analysis:
OIL Shell Helix Ultra Professional 0w-30 AV-L
MILES IN USE 5901 (9494km), 8 months
MILES 379737 (610997km)
SAMPLE TAKEN 17/10/20 (date format for the civilized part of the world: 20.10.2017)
FILTER: Purflux LS 245
wear metals (mg/kg)
WATER (%) <0.1
FUEL (%) 0.89
state of oil:
visc. @40°C (mm2/s) 59.76
visc. @100°C (mm2/s) 11.66
OXYDATION (A/cm) 3
NITRATION (A/cm) 2
SULFATION (A/cm) -
dispergency* (%) 97
SOOT INDEX** <0.1
* the german word was "Schmutztragevermögen", hope I translated that right.
** the lab has introduced the "Rußindex", an in-house tool to check for soot in
gasoline oil, as soot from direct-injection engines will not show correctly in the
standard test for diesel oils
And here is the original report. From left to right: Shell Helix Ultra 0w-30 AV-L, Shell Helix Ultra 0w-40 (twice), Aral Super Tronic 0w-40.
Soo... what happend? Wear seems ever so slightly higher. But the usage profile has changed, a few more cold starts, and a female starting driver who has a hard time coping with 32 year and 600.000km old synchromesh (we re-used my original synchronizer rings, because new ones are not available and mine, despite having the highest milage, were the best out of the three donor gearboxes). So she sometimes pulls the cold engine to 3500/min; or mercilessly lugs it when hot... but obviously, nothing broke yet.
Looking at all five UOA I have done on this engine, both the Shell AV-L and the Aral seem
to show slightly higher wear metals. The AV-L is a 0w-30 and the Aral is on the thinner side, just barely making it into 0w-40 territory. But it might also be the modern additive pakage with reduced ZDDP.
Another possibility is that there really is no increased wear - differences are very small, ad I do not how how precise and accurate the lab is. Also, you do not need to be a statistics genius to figure out that n=5 might be a bit low when you have tons of confounding variables...
So, to sum it all up:
1) It is important that there is enough and reasonably fresh oil in the engine
2) Which specific oil you run seems secondary.
3) You'd need WAY more data to be able to conclude whether one oil is better than another.
4) No, modern oil does not kill ancient engines.
For a deeper discussion, see my blog: https://turboseize.wordpress.com/2017/12...sches-motoroel/
Text is in german, but google translate might help. If it doesn't feel free to ask - I'll do my very best to answer.