engine and drivetrain Bad Oil Analysis

[john02md]

'74 2002, 70,000 original, documented miles.  20w-50 Valvoline conventional oil.  At the past two 3,000-mile oil changes, I have sent a sample to Blackstone for analysis.  Each showed, much higher than average metal content (2 - 5 times higher) - iron, lead, aluminum.  The most recent was worst than the previous.  Blackstone says run new oil 2,000 mi and send them another sample, but also advises watch oil pressure and listen for unusual sounds.  Well that inspires no confidence.  The car runs well and sounds good.  It does use about a quart of oil per thousand miles and there's an occasional puff of smoke on deceleration, presumed to be valve guide/seals.  Compression check year ago was close to 155 all 4 cylinders.  Oil pressure seems normal:

Light out within a couple seconds of cold start

VDO gauge shows:

cold fast idle 60 psi

warmed up engine 15 psi idle, 60 psi 3,000 rprm, about 75 psi 4,000 rpm

 

In the 4+ years I've owned the car, I drive it ocassionally and do roughly 3,000 mi a year.  In the 25-years prior to my purchase, it did only 10,000 miles.  A factor perhaps?

Also, in changing oil, I kept forgetting to grab the sample until near end of drain.  A factor?

Time for a tear down and analysis?

 

John

 

[jimk]

Don't panic.  Do as they say if you haven't owned the car much beyond those two oil changes you may just be seeing a washout of stuff from it's past.  Your oil can have different detergent capabilities that that of the past.  It should settle down.

 

How is you air cleaner?  Any high levels of silicon?  If so, that's a result of abrasive dirt coming in thru the carb.

[Simeon]

As Jim says, don't panic. These engines are pretty long lived (especially the bottom ends) and if yours has been regularly maintained (which it sounds like) then you are unlikely to have any immediate problems. 

 

What i I would say is that you may need to check the ZDDP (zinc) content of your oil as there is some evidence that modern formulation oils with reduced amounts can see rapid wear of cams / rockers. This would be a good point for Toby to jump in as he has some experience with this. 

[jimk]

6 minutes ago, Simeon said:

What i I would say is that you may need to check the ZDDP (zinc) content of your oil as there is some evidence that modern formulation oils with reduced amounts can see rapid wear of cams / rockers

20W-50 is excluded from the restriction on ZDDP. 10W-40 is also excluded.  The 5W-40 for European cars is not because the cars are EPA certified with the special spec oil.

[john02md]

Thanks for the comments.  In my ownership, 13,000 miles, this car has had several changes with 20w-50 Valvoline, but the two most recent are the only ones with oil analysis.  Silicon is slightly above average.  Air filter is stock sitting on an adapter for weber 32/36.  I have fashioned a foam interface to try to seal it tightly, so I doubt any significant dirt gets through.  All other elements at or below average, so the iron, aluminum and lead wear do seem puzzling. 

Also no coolant or fuel in oil sample. 

[Son of Marty]

Yes taking the sample at the end of the drain period will skew the readings especially with a car driven low miles every year the heavy particulates (iron and lead) tend to sink to the bottom of the oil pan and stick, then drain out with the last drips of oil, as stated above the bottom ends of the m10 are very stout and will generally give good warning if in distress. I also wonder if the recommended amounts they are using are geared towards a modern engine and not one 45 years old. 

[ray_]

Also, perchance you have no oil cooler, right?

 

If so, pretty hard to change all the oil....

 

Also, what they said ^

 

Cheers,

[TobyB]

Quote

 I also wonder if the recommended amounts they are using are geared towards a modern engine 

 

That's what popped into my head, too.

 

I wouldn't panic- 15psi hot with 20-50 is low- ish, but not tragic.  What's your idle RPM?

 

If it was mine, I'd pop the valve cover, look carefully at the cam and lash pads

(for your iron) and if they're ok (no scoring, troughing, etc) I'd just drive it.

 

Lead pretty much has to be bearings, and the bearings on an M10 are massively stout.  60 psi at 3000 is great for them

Don't lug the engine- as in, if it only has 20 psi at 1500, shift!

 

Aluminum is probably the oil pump housing, if it has the gearotor style.  Cam bearings, I suppose,

but they're pretty durable if the oil's changed regularly, as yours seems to be.

Pistons I suppose, but you're not hearing any slap, are you?

 

t

 

[john02md]

Idle is 900 rpm.  Cam looked good last year when I adjusted valves.  I suppose I'll just drive and observe and see how the oil looks next year.  Thanks all for your comments. 

 

Blackstone Laboratories compares engines of similar types.  So mine is compared to M10s with an average of 3,300 miles on the oil.  I don't know how large their database is, but I periodically send them samples from my other BMWs and they always compare to similar engines.  Compared to my S52, and Blackstone's "universal" averages, for example, my M10 results would be really, really awful.  The test also shows how the oil is holding up, suggesting how long you can go between oil changes.  Obviously with the M10, the concern is wear, not oil longevity. 

[avoirdupois]

Sitting for long periods followed by "dry" starts can be a curse.  So can short runs or failing to run the engine to normal operating temperature before parking it.  This can be especially true if the engine has been fed a rich (cold start/choke on) mixture as this tends to promote oil contamination, among other detriments to long engine life.

 

Next time you change your oil, insert a cotton swab through the oil sump drain hole and gently "swab" the bottom of the pan.  You probably won't like what you see on the tip.  The pan bottom can be difficult to clean without physical intervention (removal).  Flushing the engine with light weight oil and solvents can rid the engine of considerable crud, but it rarely gets everything at the bottom.   This condition can tend to make fresh oil look prematurely "used" in short order.  Since you are diligent enough to perform routine oil analysis, you might consider removing the pan and cleaning it.  This might resolve lingering doubts about cross contamination of your oil samples.  Otherwise, you might consider driving for another 40 years before worrying (too much) about the consequences.

 

Edited November 1, 2016 by avoirdupois