Help me decide Mobil 1 0W40

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Feb 16, 2003
OK..I need some feedback. Pretty big chunks of cast iron and steel severe sliding wear in my Vortec V6 1998 GMC Sierra oil sample. I'm thinking of switching to Mobil 1 0W40 SuperSyn for extra wear protection and thicker oil wedge. Any responses? You think this will void my warranty if I switch?

p.s. slow leak of glycol into the engine as well, which will be repaired under Optimum Warranty.
Pretty big chunks of cast iron and steel severe sliding wear.


If you have a coolant leak, no oil will do good. Sorry. Your only choice is to change your oil often, and doing this, I don't believe Mobil1 would be cost effective.

Have you considered an over-the-counter stop leak?

[ October 24, 2003, 12:22 AM: Message edited by: Jelly ]
Jelly, Of course I'm getting the leak fixed before I switch oils (that is if the leak can be found). The oil has been drained and replaced with cheapo oil a few times in the past week to monitor wear and glycol levels. And..I think I'd rather get the problem fixed or return the vehicle rather than resorting to a quick-fix of leak-stop. Thanks.
Sounds like you're mad at me or something?

What's with the "pretty big chunks of cast iron and steel severe sliding wear" line though? I don't believe I understand this.
I'm not mad at you, just frustrated at the whole situation. The "big chunk wear"...I guess it's Ferrography Analyst talk. I'm trying to figure out where the wear is coming from and if it is worth keeping the vehicle or not.
Get that coolant leak fixed ASAP! Some retail stores including Walmart don't even put the viscosity of the oil you purchased on the receipt. The last time I bought oil from Walmart the receipt only said Mobil SuperSyn and Castrol Syntec. If the warranty company were to ask what oil you put in just say the name brand and 5W-30 if you are worried. It is extremely rare for a dealer or repair shop to have a UOA performed to verify that the recommended grade and viscosity motor oil was used. A few years ago I had a POS 1997 Plymouth Breeze that required TWO engine rebuilds by the time it had about 80,000 miles and I never had to show any oil change reciepts before they rebuilt the engine under warranty (I had the Chrysler extended warranty).

I think it would be helpful to remove any build-up of crud in your motor after you have had the coolant leak repaired and before you put the Mobil SuperSyn in your truck. You may want to try AutoRX of just use Gunk engine cleaner and carefully follow the directions. I do believe you will have less engine wear with Mobil SuperSyn 0W-40 than with a typical 30 weight motor oil. The GM 4.3L V6 is based on the old design 5.7L V8 engine that is as old as the hills and should benefit from a higher viscosity motor oil at high engine temperatures.

[ October 24, 2003, 01:04 AM: Message edited by: Sin City ]
Thanks. Actually, I can see a conflict of interest, with me being the lab analyst checking the oil of my own truck and submitting my report to the Dealer. They were supposed to pressure test it today, but instead, just changed the oil and sent away the oil to another lab for confirmation, but I told them I don't know what the lab will see because there is only 300 km on the new oil. When I checked it the previous two times, it was bad. I'm supposed to know by tomorrow if they're fixing it..and if not, it's going back to them.

I would think that the high wear in this engine is/was caused by the coolant contamination. As you probably know, this will cause wear numbers to shoot through the roof.

I have a 4.3L V-6 as well (in a 1500 Chevy though), and I run Pennzoil Long-Life 15w-40, but it doesn't have the cold-pumping capability you need to have in Canada.

For the 4.3L, I'd suggest Rotella-T 5w-40. $12.88/gallon at Wal-Mart.

[ October 24, 2003, 01:04 AM: Message edited by: Jelly ]
Thanks Jelly,

Who knows how long it's been leaking in, and you're very right about it possibly being long term erosive wear from the glycol. I'd love to keep the truck, so once the leak is fixed, I'll monitor it closely and try a bit more lube protection. Thanks for the info.

Good night.
Since the Rotella-T 5W-40 is much cheaper than Mobil 1 you might as well use the Rotella-T. In Canada Rotella-T will most likely cost more than the USA price of $12.88 a gallon but it should still be far less expensive than Mobil 1 0W-40. I think you will get about the same engine wear with either oil.
Ah - another victim of the infamouse Death Cool. Other than this terrible engineering mistake, GM motors are super rugged. But if this truck is new to you and its been leaking coolant into the crankcase for a while, you may have some serious issues. Bearings are typically your first major item to be degraded by coolant, but you didn't mention how you lead numbers look. Is lead low?

Basically when your dealer repairs the coolant leak, they need to pull the oil pan and check the main bearings with plastigage. If the mains are good, you can bet the rest of the bottom end is good. Get these jokers to fix your truck this week and get your sales person involved. Tell the sales mangaer that you want it fixed properly, bearings checked and all, or you want a different vehicle. That sales person isn't gonna want to lose commision, so they'll beat up the service dept to make you happy. Be ruthless if you have to! Good Luck!
Doubt you need the thicker oil...most certainly the wear is due to the leak.
severe wear and chunks?!?
If it were me, I'd do what crashz suggests. No way I would keep the vehicle after this. Simply repairing the leak is not enough now and it is under warranty, that's completely unacceptable.
Don't know how long it's been leaking in?
An analyst that doesn't do trend analysis on their own vehicles?...Betcha wish you did now

Good luck!
How can I trend my own vehicle when I just purchased it two weeks ago. I already thought I overkilled on the analysis. I haven't kept the oil in long enough to check the lead numbers, but I think it'll be going back.

You want to hear the funny thing? I've had lots of training by Noria and Predict DLI on Machinery Lubrication and Oil Analysis and the lab where they sent it for a second opinion came back with negative glycol. Go figure. I tested positive on three different occasions after 3 oil flushes and of course ran a blank new oil with each batch for quality control. Ya think it was a convenient sampling problem by the weasel in the service dept? HELP>>>>>>> WE only have exchange warranty, but they don't have any other trucks that we want. However, the powertrain warranty does come with full engine overhaul if necessary.

These 4.3L, vortec engines always generate a lot of iron - it's not uncommon to see wear rates of 5-7 ppm/1000 miles. Very slow coolant leaks normally result in increased bearing wear, but not necessarily the type of rubbing wear you are talking about.

Since you live in Canada, I'd go to Walmart and get some Delvac 1, 5w-40. Use that and see if it's possible to re-establish a normal wear pattern. It may be possible to stabilize the situation. Delvac 1 is a 12+ TBN oil, so it will do a better job of handling the coolant contamination.

I'd also be interested in what the K and Na levels are? As you know, EG reacts chemically with the engine oil and doesn't always give you a positive result on a glycol test. But the trace elements like potassium/sodium/boron are almost always present in the sample.
Thanks for all of the valuable comments guys! Nothing better to do on a Friday night, I'm back from work testing my own oil once more! Not only has the glycol increased, but a flashpoint shows approx 0.5% fuel dilution on only 500 km. Worn ring/liners ya think? And the decision is......truck is going back (no haggle/no hassle return). I'm waiting on my Na/K/B results just for the heck of it.

Lesson learned...always check before you sign on the dotted line.

Originally posted by lubechick:
-*-*-*I'm thinking of switching to Mobil 1 0W40 SuperSyn for extra wear protection and thicker oil wedge. Any responses? *-*-*

Youre in the lab, could you get a few ounces of a good VI-improver ?? what about going that route?
If it were me, and I had a problem like this, I would make sure it's clean as possible... flush, and run several short oil changes before anything is done IMO...
1. Get it clean
2. Establish a trend/ BASE-line
3. Go from there
If a doctor in the E.R. were to handle a gunshot wound, I think they would 1. control bleeding 2. get all the slugs out 3. try to make the perosn as stable as possible 4. Go from there.

If you are limited with the return policy timewise I would tend to agree and return it asap. I'm sure the worry just isn't worth it. If they aren't going to fix it now, how are they going to act when you can't return it?

Just my 2c worth.

Thanks. I think I needed that. WE have 1000 km before we have to return it. That'll buy me some time to look for another cuz it's only an exchange policy. Maybe it'll die before then and I'll say..."TOLD YA SO" to the service dude who won't consider my results because i'm cheating the system or something stupid like that.
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