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Originally posted by TomJones76:
quote:
Originally posted by TheFuror:
A service writer at the local Chevy dealer made it quite clear that in his not-so-humble-opnion, if GM recommends 5w-30, then that is what to run. He explained that there is more to it than ambient temperature, such as bearing clearances, etc.
You do realize this service writer was factually impaired, right?
At ambient temperatures above freezing, you should expect a 5W30 and a 10W30 that are both within their respective grades to perform in *EXACTLY* the same fashion.
I think it important to understand that the stated preference for 5w-30 comes directly from General Motors and that the service writer is basing his recommendation on that.
The owners manual that I have for both a 1998 Silverado and a 2004 Avalanche state in no uncertain terms that the clear preference is for 5w-30 and to use 10w-30 only if 1) the temperature is above 0 degrees F; and 2) 5w-30 cannot be found.
Having said that, I am not suggesting that I know the answer to this question. Indeed, I am still in a quandry as to which weight to run.
Here's why: BITOG has many, many people (who seem to know what they are talking about) say that, as a general rule, 10w-30 gives significantly better protection than 5w-30, and as long as the temp is above freezing, to run 10w-30. Lots of other folks (who also seem to know what they are doing) say that 10w-30 is really obsolete, given the actual numbers, and that 5w-30 gives your motor all it would need, have a nice day.
I have looked at several motor oils and at least with respect to most synthetics, the numbers between the two grades are very similar (40C and 100C vis, along with HT/HS).
In the end, I suppose it may not really matter. I just am trying to keep this $30K vehicle running so my oldest can take it to college in 7 years.
I know, we can only dream....
Thanx
Bob W. a.k.a., "TheFuror".