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GM Viscosity Requirement
- Thread starter yankees1
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Sounds like you have a red phone to everyone...how’s the president doing?
And GM is GM and no need to slate a very well known and reliable product (SAAB is GM too, bet you think they are trash too
Here.....
Hope some people actually read that article. They at least got this part right.
In the case of the famous GM piston slap engine defect, the piston design with hypereutectic (high silicon content aluminum alloy) pistons, reduced or eliminated piston skirts (to reduce reciprocating mass), and a higher ring pack to reduce unburned fuel mixture on the sides of the piston crown have made piston to cylinder bore fit much more critical. The amount of tolerance (variation or margin) in allowable clearance between the piston and cylinder bore to prevent audible piston slap has been reduced by a factor of at least 50%. Consistently hitting the narrower margin for piston to cylinder bore tolerance has not happened for GM during mass production. Thus, some engines have no audible piston slap and some have piston slap on only one or two cylinders. What might have looked really good in testing of hand built engines in the lab hasn't transferred to the production line of this corporate giant.
If you want to call this a design issue, then virtually every new engine built today has a design issue, since the vast majority of new engines built today have hypereutectic short piston skirts with high ring packs.
Oh really? Might want to tell these Tundra owners it's just their imagination.
http://www.tundrasolutions.com/forums/tundra/80137-tundra-engine-noise/
It is piston SLAP. Seems Toyota has joined the ranks with GM as far as sloppy engine assembly goes.
My '04 does it too sometimes, really sounds like chit.
Piston slap is caused by too much clearance between the piston and cylinder when cold causing the piston to slap or rock in the cylinders.
GC 0w30 is thicker at almost every temperature than virtully any GF-3/GF-4 SL/SM 5w30 or 10w30 on the market. GC 0w30 will only start to become comparatively thinner when the temps get below -25°C/-13°F.
You people need to learn to look at the specs, not simply the grade designations. And there will be other properties besides viscosity that will affect "start-up film thickness".
Thin oil for closer clearances. So it's not all CAFE afterall.
Do pistons push thick oil out of the bores before ring pack can collect some?
Do pistons push thick oil out of the bores before ring pack can collect some?
How do you know for sure it’s a manufacturing problem? Have you seen the component drawings? Have you seen any measurement data on the parts? Do you know for sure that the parts do not meet the prints? IOW, do you have anything other than your opinion to back up your statement that GMs piston slap problems are a manufacturing quality problem?
GM may not "design in piston slap or any other noise on purpose", but based on the thousands of their products on the road, they are obviously quite tolerant of it and typically unwilling to do much about it. If you complain about it, you're quickly told it's acceptable and/or normal. They may not have designed it in, but it appears they aren't concerned enough to design it out either.
Agreed
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Agreed
Like what makes hot oil "stickey"? Additives.
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