Need help from folks with 5W-40 Mobil 1 / Delvac 1 experience

[Eiron]

I've got a question about the viability of using this oil under questionable circumstances. I just had a UOA done & it came back with high viscosity (18.7 cSt) & low TBN (3.0). The lab had this to say about it:

quote:

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The only two things that thicken viscosity are antifreeze (which you did not have) and extended oil drain. An extended oil drain would cause high oxidation which thickens the oil. ... Oxidation is caused by overheating, a coolant problem (bad coolant), or extended oil drain. On the last sample you had 4820 miles on the oil, this sample had 8498 almost double. Low TBN indicates that the oil condition is poor - the oil additives are being used up and the oil is losing its ability to neutralize acids. Again, I would check for overheating and/or check you coolant to see if there is a problem.

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Based on the reasons they gave for thickening (coolant contamination or gross oxidation) & a little research into the failure/repair history of this Saab model, I realized the probable cause was overheating due a faulty thermostat &/or Engine Coolant Temperature Sensor. The local Saab garage told me they recommend replacing both components "every couple of years, to avoid problems" & ours are now 6+yrs/63k miles old. I've got the new parts & will replace them in the next day or two.

I changed both the oil & filter in mid-July when I sent in the last sample. I wasn't aware of the engine temp problem at that time. We then went from Denver to St. Louis & back, & after one month we now have about 3,000 miles on this new oil. This weekend we're leaving from Denver to go to Phoenix for a week, so we'll easily put another 2,000 miles on the car by the time we return. I'm sure this is one of the absolute best oils available & I'd like to continue using this batch for a full 10k mile interval if it's safe to do so. Obviously, it's not worth sacrificing the engine bearings or turbo just to extend the OCI, but I'd also hate to dump out $25 of good PAO oil & filter if I don't have to.

FWIW, the UOA came back with excellent wear numbers. Even with the high oxidation/thickening & low TBN, iron & lead were both about 1/4 of what they were using M1 0W-40 for the same OCI. Based on the overall results you've seen with this oil, what would you guys recommend I do with the stuff that's still in the engine?

 

[Raven18940]

Which model and year saab? I know the newer (98-on, new being relative to old saabs) Ecopower 4 cylinder has a lot of blow-by gasses due to thin piston rings. The PCV system is no where near up to the task of handling it to compound the problem. I think this is what is causing your oil thickening problem, not the coolant.

Just think, if you had been using a lesser oil it would have long been sludged up, and you're still short of the 10K drain interval Saab called for.

I keep my 9-5 on 3K OCI, which is over kill I know, but I haven't done a UOA on the new M1 5W-40 yet and I drive my car pretty hard. If 5K worked out well last time for you, it sounds like you'll be getting back just in time to change it.

 

[JHZR2]

consider first the obvious... lab error. Just a thought.

Id certainly consider doping your oil with LC, regardless of finding of a solution or not; it ought to help hold TBN better and reduce oxidative thickening.

I think you would notice if something was really off temperature wise or otherwise... maybe not though. Check first things first - fuel economy (do you log it?), PCV valve, EGR valve, etc.

Take it from there... If you end up with 5000 mile OCIs, it isnt the end of the world...

But also consider using other oils.

JMH

 

[Gary Allan]

This will be the first time that I've seen any substantial impact on this oil in just about any service. I don't quite get their exception to the TBN ...although it is lower than I would expect with D1/TSUV. I would expect this TBN @ about 14k. This is a common TBN for GC @ 7500 miles ..and they don't flag it as being "low".


I'd surely do a double take and consider the lab error angle. Otherwise, you've done what I thought was relatively impossible.

 

[Pablo]

call 1-800-oil-doug

Lower iron than M1 0W-40? Who knew?

Seriously - the engine overheated enough to cook the oil and you didn't notice it????

 

[ruking77]

The good news is the oil analysis did what it was designed to do: given consistent intervals; detect problems with engine systems BEFORE catastrophic failure. The bad news is that Mobil One Truck and Suv 5w40 AS GOOD AS IT IS, is not a magic bullet that can prevent catastrophic system/s failure.

 

[Mickey_M]

quote:

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Eiron:
.... I just had a UOA done & it came back with high viscosity (18.7 cSt) & low TBN (3.0). .... I changed both the oil & filter in mid-July when I sent in the last sample. I wasn't aware of the engine temp problem at that time. .... we now have about 3,000 miles on this new oil. ..... we'll easily put another 2,000 miles on the car by the time we return. .... what would you guys recommend I do with the stuff that's still in the engine?

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The increase in viscosity is normally exponential, not linear.

Most of thickening probably ocurred in the last quarter or third of the previous oil's life.

I'd run it to 5,000 or so and then dump it.

At that point if you still get a high viscosity number, you might want to look for some other problem.

It takes a lot of heat over a long period of time to thicken Delvac 1. You may have a blockage or mechanical problem somewhere that's causing a hot spot.


.

 

[Raven18940]

Oh, nevermind what I said about the piston rings and PCV system. The temp gauge on a Saab should always be dead center. I don't think your t'stat was bad, just your car was just getting heat soaked without it's fan. Thank Mobil 1 for their fantastic oil and Saab for their gigantic stock oil cooler.

This thread is motivating me to change my t'stat and temp sender. It's been a little flakey twice in the past few months. I'll be driving along, temp reading perfectly normal, then it just drops to ice cold.

Then the next time I start the car the temp gauge goes "I'm fine" and works perfectly normally again.

Bizarre car sometimes.

www.saabcentral.com this site has a really good forum if you ever need help with anything on your Saab.

 

[Eiron]

quote:

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Originally posted by Raven18940:
... I'll be driving along, temp reading perfectly normal, then it just drops to ice cold. ...

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This is exactly what mine was doing. Since this started happening well before I reached 60k mi, I've now added the t'stat & ECTS to my 30k mi maintenance list.

Thanks for the SaabCentral link. I usually get my info from TSN.

 

[Raven18940]

Well for now my fan is still coming on so I'm not super worried, but I'll definately have to replace those soon. Good excuse to change the coolant as well. Got any tips on replacing the t'stat I should know?

Best of luck with your Saab.

 

[Eiron]

Not sure with the 9-5s. For the 9-3 4 cyl, removing the turbo delivery pipe & the mounting bracket for the electrical connectors helped a lot. Having a u-joint for the socket helped too. After that, it was simply a matter of unbolting & bending the bracket for one of the minor coolant lines (it was bolted to the t'stat housing) & pulling the coolant hose off the housing. The ECTS is below/next to the t'stat on my '99 engine.

 

[Eiron]

OK, well I guess I'm going to dump this load before we leave on our trip. I've talked a little more with both the lab mgr & the account rep (he also drives Saabs & uses made-by-Mobil CAT 5W-40 syn), & they both recommended dumping the oil after I get the problem fixed.

I got the t'stat installed last night after work, but the ECTS was the wrong one so I need to exchange it & install that tonight. Hopefully I'll have time to change the oil tonight as well. Yes, I'm glad for both having UOAs done and running M1 5W-40!!! The last UOA told me something was wrong when I otherwise would've ignored my erratic (frequently low) temp gauge, & the 5W-40 protected the engine & turbo beyond what other oils would've.

To answer some of the questions:
Lab error: My 1st thought was that they gave me someone else's results. When I asked, the lab said they ran it twice before they sent my report.
Overheating: I've learned that the ECTS (fan switch) goes out on this engine. I think this is the same sending unit for the dash gauge, so if it's bad it could show either too low or too high. (Mine showed low.) Since this also controls the fan, that may not be running when it should. Another possibilty for the thickening might've occurred after shut-off. When I learned about the problem, I realized that for the past several months the fan had not been running after the car got shut off. There's no way to know if the fan should've been running (having the A/C on automatically runs the fan anyway), but if the engine's hotter than normal this would've let the oil & coolant just sit in the turbo & cook.

I hope to have time to post this latest UOA either today or tomorrow. As I mentioned, the wear was stellar even with the overheating problem.