What is sufficient high temp shear level?

Greetings: In researching the issue of what oil (synth versus dino) and what weight (5w-30 versus 10w-30) to use I have decided to run Castrol Syntec but am debating what weight. I have a 2004 Chevy Avalanche with a 5.3L V8. I see that the 10w-30 has better High temp/High shear numbers than the 5w-30 (3.1 versus 2.9), however both are in the SAE range of min 2.9 to max 3.5 (ACEA A1, A5, ranges as well). My question is does a HT/HS number of 2.9, do an adequate job of protecting the bearings, etc. or would it be worthwhile to go to a weight with a higher number? Both Syntec weights pass the GM 6094M (light truck) and GM 4718m (Corevette) standards. Also, it is not particularly cold where I live (generally ambient temp in winter does not get much lower than freezing) but the manual states a preference for 5w-30. I elected to go with Syntec as the numbers look good on paper and with the UOA's I have seen. And for what I do, wear protection seems more important than temperature tolerance, hence Mobil1 made a very close second. Yes, AMSOIL is a great product, yes it has great numbers, yes it has a cool name, but the product with the great numbers is not API certified and the potential warranty issues rule it out for me. Thanx in adavance. Bob W.
 
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quote:
Originally posted by TheFuror: What is sufficient high temp shear level?
If you're to believe the API, you need nearly a 3.0 HT/HS viscosity to get the job done. IMHO, although it will reduce fuel economy by some margin, I'd get the highest HT/HS possible for high levels of protection.
 
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quote:
Originally posted by Pick: I keep hearing that Amsoil 5W30 is NOT API certified. The jugs I have say it is. Will post photo if someone needs proof.
[Off Topic!] Are you talking about the XLF (XL-7500 5W30) or the ASL 5W30? ASL, TSO, & ATM are not API certified. AMSOIL says they are to be used where it calls for API SL, etc. The packaging even says API SL, but it doesn't have the API doughnut on the back of the bottle, unless it's the XL-7500.
 

TheFuror

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quote:
Originally posted by Jelly: [QUOTE]Originally posted by TheFuror: [qb] What is sufficient high temp shear level?
If you're to believe the API, you need nearly a 3.0 HT/HS viscosity to get the job done. Well, I looked that API and ACEA specs, and it says that the minimum is 2.9 and maximum is 3.5. I just wondered if one should go that close to the minimum level and whether that minimum level establishes a standard that equates to "good" as opposed to "just cutitn' it"
 
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quote:
Originally posted by TheFuror: Also, it is not particularly cold where I live (generally ambient temp in winter does not get much lower than freezing) but the manual states a preference for 5w-30.
Given that, I see absolutely no need for 5w30. I would even look around for a 10w30 with higher HT/HS. I believe some of the High Mileage (HM) oils are a bit higher. Castrol has a HM oil, or maybe Citgo Ultraguard 10w30.
 
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I've been using Syntec 5w-30 in my Dakota with nice results. I live in the high desert of So Cal and it's flippin' HOT.(100*+ daily) It's my personal opinion that some people take way too much stock in the lab #'s of an oil. (i.e. HT/HS 2.9 vs 3.1 [Wink] ) For me if it works, it works. If it's a group III or a group IX base oil makes no difference to me. Flame suit on! [Cheers!] Darryl [Patriot]
 
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