GM manual says "do not use" 10W40

[outrun]

Thier are many posts of users that "safely" use 10W40 weights in lieu of the OEM recommended 30 weights.

Looking at the GM Service manuals of:

-1993 Oldsmobile Regency Elite Ninety-Eight

(3800 TPI Supercharged and Naturally Aspirated Motors)

-1998 Chevrolet Camaro

(3800 Series II V6 cast-iron and 5700 LS1 alum)

The records came to the point that essentially the V6 engines recommended 10W30 year round but 5W30 for temperatures below 0C or 30F and further suggested.


The 1998 manual suggested 5W30 year round for the LS1 engines. For the V6 engines it sustained the 10W30 year round recommendation. Interesting as it suggested switching to SYNTHETIC of 5W30 or 0W30 for extreme cold conditions. Food for thought for those that still question the superior nature of synthetic lubricants

In both manuals though it was specifically stated NOT to use 10W40 weight oils

Any comments on why? Was it the engineers at GM that new something we do not? Or is it the bean-counters haggling over fuel economy?

Thanks yall-

 

[jason07-1zzfe]

They will not get CAFE credits from the EPA if they do not state that.

 

[Patman]

The best oil analysis results I have seen so far on an LS1 engine have been with 10w40 Castrol GTX. This was on a 99 Trans Am with 75,000 miles on it.

He ran a short 2500 mile interval, but even with very hard driving the iron was only 3ppm, lead was only 3ppm and aluminum only 3ppm. Copper was only 5ppm.

The oil had thinned out to 12.1cst by the end of the interval, but GTX 10w40 starts out at around 14. So for most of this oil's life it was a low 40wt. This analysis is part of the reason I believe the LS1 and LT1 engine (ones with slightly higher miles anyways) like an oil closer to 12-13cst.

 

[outrun]

Patman,

Interesting analysis data. From reading all the post however it is my understanding that LS1 modular engines will have obnoxious Cu levels for at least th 1st 35,000 miles.

Essentially the question I am alluding to in your post is that did he use a 30 weight before or after the 10W40 GTX test?

Was there a significant difference in the values?

and by the way Castrol corporate philosophy mind boggles me. Castrol GTX is a great dino oil...but from this same maker they make Syntec a Group III "synthetic." I would think a PAO OTC would only be natural by Castrol to compete with Mobil-1...they should start printing on bottled oil if it is PAO or Group III hydrocracked.

 

[G-MAN]

The manual for my 97 Olds van says don't use 20w50, but it doesn't mention 10w40.

Keep in mind that up until the mid 90s, the standard way to create a conventional 10w40 oil was to use essentially the same base stock as a 10w30 but just use more VI improver. In the early 80s, this was a recipe for disaster as many GM engines suffered premature camshaft wear using 10w40 and that was the reason GM universally started recommending this grade not be used. However, with the advent of Group II and Group II+ base oils, which tend to have a higher natural VI, 10w40 oils can now be produced without extreme doses of VI improver. Therefore, modern 10w40s are pretty much as "safe" to use as 10w30s.

 

[Patman]

quote:

---

Originally posted by outrun:


Essentially the question I am alluding to in your post is that did he use a 30 weight before or after the 10W40 GTX test?

Was there a significant difference in the values?

---

I emailed him last week and he mentioned he's now running 5w30 GTX and will post the results from Blackstone when he's finished the interval. It should be very interesting to compare to the 10w40 numbers!

 

[Dr. T]

I agree. This was "in the days when" 10-40 was a huge spread and the oil broke down fast leaving serious deposits and so manufacturers recommended against them.

Interestingly enough, a friend of mine said he bought a car in which the previous owner use Castrol 10-40 and it created serious sludge buildup.

As far as Syntec...they won the lawsuit, group III's are "synthesized" and so they're labelled synthetic. Look at the stats, Syntec vs. M-1...they aren't too different. I'm not sure about the Oil Analysis...but it seem like there's an equal amount of anti-M1 posts here as well... In either case everyone else's OTC synthetics are group III now anyways...My guess is they probably perform about equal give or take a few points.

 

[Dr. T]

Ooops...forgot to add. I agree...M-1 should have cashed in on the lawsuit by advertising they're the only PAO OTC available....etc, etc. Maybe they think the public is stupid.

Interstingly enough, the new bottles of Havoline state "created from advanced Group II basestock..."....

 

[G-MAN]

quote:

---

Originally posted by Dr. T:
Look at the stats, Syntec vs. M-1...they aren't too different.

---

What?!

You need to look again. Syntec has got awful pour point and CCV numbers that don't even come close to Mobil 1's. Heck, even Pennzoil's "conventional" oil has a lower pour point than Castrol's Syntec.

 

[Patman]

I saw a Syntec report recently where their 10w30 had sheared down to a 20wt! No fuel dilution either. And it was in just 3000 miles also. Not good.

 

[Dr. T]

Pour points are for bragging rights. CCS numbers are what matter more. Who cares about M-1 -50F Pour point, when it can only pump at roughly the same temp. as others oils of the same viscosity. ie. try 15-50 at -25 F, your engine won't even turn over because the oil is so thick...but, hey it'll 'pour'.

As far as thinning out...we've seen that with M-1 5-30 too.

 

[WeyounDS9]

quote:

---

Originally posted by Patman:
I saw a Syntec report recently where their 10w30 had sheared down to a 20wt! No fuel dilution either. And it was in just 3000 miles also. Not good.

---

That one was on Maxima.org I think.
I saw it too.
Quite an inditement.


Fred...

 

[Ray H]

quote:

---

Originally posted by Dr. T:
...M-1 should have cashed in on the lawsuit by advertising they're the only PAO OTC available....etc, etc. Maybe they think the public is stupid...

---

Actually it wasn't a lawsuit. Castrol and Mobil's dispute was arbitrated by the National Advertising Division of the Better Business Bureau. The parties agreed beforehand to abide by the NAD's results, but no money changed hands as might be provided by a civil court settlement. Mobil DID attempt to capitalize on the results. For awhile, at least, the Mobil 1 website had an online reprint of an editorial in the November 2000 issue of Car and Driver. Patrick Bedard outlined the differences between traditional synthetics (PAOs) and the hydrogen isomerized "synthetics" (Group IIIs) and implied in his conclusion that Castrol was enjoying an unfair windfall since Group IIIs were cheaper to produce than PAOs, but the company wasn't passing the savings along to consumers. I have the entire article if anyone wants me to post it.

-Ray Haeffele

 

[Ron]

Well, ya'll can hammer away at Castrol Syntec all you want.Some Blackstone numbers to the contrary were posted on 5w-50 Syntec back in August.I've switched to Havoline Syn 5w-40 it's cheaper anyway.
Ron

 

[Patman]

quote:

---

Originally posted by palmerwmd:

quote:

---

Originally posted by Patman:
I saw a Syntec report recently where their 10w30 had sheared down to a 20wt! No fuel dilution either. And it was in just 3000 miles also. Not good.

---

That one was on Maxima.org I think.
I saw it too.
Quite an inditement.


Fred...

---

Actually the one I saw was of an LS1 f-body, so it's a different bad Syntec analysis. I've yet to see any good ones on Syntec.

Despite that fact, I still plan on running two 6000 mile intervals of Syntec 5w30 in my sister's 99 Civic. This will be after the current 6k interval with Mobil 1 SL TriSynthetic, then two 6k intervals with GTX first. After the Syntec intervals I will then go with Mobil 1 SuperSyn. My sister drives quite a lot and all highway too so the results should come pretty fast.

 

[G-MAN]

Ray H,

The link to the article by Beddard is still on the Mobil 1 website.

 

[Rick]

So what is a better synthetic PAOs or Group 3?

 

[G-MAN]

quote:

---

Originally posted by rick:
So what is a better synthetic PAOs or Group 3?

---

Now that's a question!

In general, PAO based oils will shine in extremely low temp conditions and in extremely hi temp conditions. Under most conditions, I believe a well-formulated Group III oil will protect as well as a PAO based oil. I'm currently using a Group III synthetic (Rotella T Synthetic), but I probably won't continue to use it because the price has increased. I'm not going to pay a PAO price for a Group III oil, even if it's based on Shell's excellent XHVI wax isomerate—though I could change my mind.

(I'm known to do that from time to time. hehe)

 

[Rick]

Is mobil 1 group 3 or PAO, what about Royal Purple?

 

[G-MAN]

quote:

---

Originally posted by rick:
Is mobil 1 group 3 or PAO, what about Royal Purple?

---

Mobil 1 and Royal Purple use Group IV (PAO) and Group V (esters) in their base oil blends. Royal Purple, however, uses some Group I as the additive carrier oil. Mobil 1 doesn't.