why cant you get Valvoline 5w 50 in the US ?

desmo01 said:

I run M1 5w50. Been hard to find so I mix M1 10w30 25% and M1 15w50 75% to get about the same thing.

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That's interesting - how does mixing a 10Wxx and 15Wxx ends up being 5Wxx (thinner) cold rating? Seems backwards to me but I haven't read about mixing oils either.

desmo01 said:

Anyone know what the factory fill viscosity was?

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5W30 per TIS, but they also warned not to go over 5-6k rpm (if memory is right) until the first oil change to 10w60.

desmo01 said:

Having done a great deal of plain bearing development (and yes on rod bearings too), the clearance is poorly chosen (too tight) for that oil viscosity.

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Now I agree with the clearance poorly chosen statement. But the little evidence I've seen does not support the second half of your statement which suggests different viscosity would solve the problem. A factor I'm sure, but a minor one based on evidence. These two examples come to mind / found in 5 minutes of searching:

If viscosity was the only problem then hotter climates would have less or no bearing issues using 10w60 right? Guess not:
"Hi all I replaced my rod bearings over the weekend and have something to add to whether rod bearings wear in Australia or not debate. I live in Central NSW and I have a 2005 m5 with 140,000km (87,000miles) pretty good service history spent most of its life in south East Queensland i think this goes to show that climate doesn't mean anything and if you are in Australia and are wondering if you should replace them or not you probably should"


Since you like 5w-50 then 0W-40 should def be light enough right? Think again:
"This as a set of WPC treated 702/703 bearings from an S85 with 14k Miles on them, removed at 82k miles. M1 0w-40, 5k mile OCI, modified tune to prevent revs above 4K RPM until over 180F oil temp. Religious warm up routine, daily driven with car seats in back, no shenanigans.


I could go on but there's enough threads out there about oil and rod bearings. Yes clearance is too tight, thinner oil is not a 'solution enough'. I'll prob stay away from further discussion also, we use what we want carry on...

I mean OP wants to use 'royal purple XPR the best oil'. Who TF am I to say otherwise???

It is a bit thicker at cold temps, not too much. There's a few viscosity calculators to determine resultant viscosities online. I otherwise would run M1 5w50, a path I have chosen as the wear resulting from 'oil starvation' of the bearing has probably already taken place, and things settled in with thicker oil. Once I change bearings I'll run thinner stuff, probably M1 10w30.

Clearance and viscosity are what really drives bearing oil flow. Pressure does also of course, but for equivalent pressure that's what it's a function of. That statement is based on numerous tests, on numerous engines testing those direct variables. I did this type of work for a living for ~20 years, now in another, but similar field.

Hotter climes don't really matter as much as one might think. What does matter is the bearing temp itself. On this type of crank you can pretty much bet on bearing/oil temps as follows:
Mains are oil supply temp +50F
Rods are oil supply temp +100F

Note that the HTHS viscosities are quoted approximately at rod bearing temperatures, you might compare what the viscosities actually are in the bearing for various oils.

If the 702/703 bearings are the tin/aluminide ones you don't really want them. They are undesirable as they fatigue, and liberate chunks of the plated material from the steel bearing backing. WPC does have its place, and I have used it to good effect in my professional life, but I would not do so on rod bearings.

I have run 0w40 for a change on one of my cars, didn't see VANOS missing target, so I'm not sure what may go awry at lower (i.e., 5w30) viscosity.....but I will say this, the tribological pinch points of an engine are generally not the rod bearings. They are typically over the cam nose at hot idle, and TDC firing of the top ring at peak torque.

desmo01 said:

I otherwise would run M1 5w50, a path I have chosen as the wear resulting from 'oil starvation' of the bearing has probably already taken place, and things settled in with thicker oil.

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This is something I've mentioned in the past - do bearings go thru an initial wear phase then settle, at which point what you use is irrelevant / damage is done. If so then unless you bought the car new and stuck to the factory fill 5w-30 there's no point in changing oils. Did bmw do this on purpose, by design? Pretty dumb if you ask me, but of course hindsight is always 20/20.

FYI this is how honeycomb edge seals on jet engines break-in. Upon initial assembly rotors can't even spin.

desmo01 said:

Now, new bearings at original clearances? The absolute thickest I'd run is 0w40.

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Wish anyone had evidence to support 0w40 being good enough. But if it hasn't happened by now I guess it's never happenning. The one (Jcolley) data point I posted above used 0w40 on brand new bearings just to end up with wear similar to 10w60.

And as you prev pointed out since the typical constraints are hot cam at idle and piston rings how does thinner oil impact them in the long run?

Given there is several examples posted of BE bearings with no wear using 10w60 I know which path I chose. I don't have to wonder about cam or piston ring wear either. In fact I've never seen pictures of worn BE bearings. If they existed all forums and FB groups would be all over them. Let's also not forget the conrod side clearance is also tighter than normal. How much impact does it have on oil flow? Suppose the BE examples out there suggest it doesn't matter.

Food for thought.

"This is something I've mentioned in the past - do bearings go thru an initial wear phase then settle, at which point what you use is irrelevant / damage is done. If so then unless you bought the car new and stuck to the factory fill 5w-30 there's no point in changing oils. Did bmw do this on purpose, by design? Pretty dumb if you ask me, but of course hindsight is always 20/20."
Fundamentally yes. Also one of the dumb things BMW has done like the damned biodegradable wiring.
Think the conrod side clearance was on the order of 0.008", not concerned there.

Now as for:
"FYI this is how honeycomb edge seals on jet engines break-in. Upon initial assembly rotors can't even spin."



Yowza!! You must have worked on different stuff than I do/did!!!
Can't say I was aware of any gas turbine places in the Chicongo area.