GM 4718M, what is it?

[Patman]

I know that this is the test for oils that are approved for use in the Corvette, but what exactly does this test involve?

 

[mojo]

GM4718M is the Passenger Car Engine OIl Specification that is their factory fill and service fill engine oil. It covers both grades 5W-30 and 10W-30 SG/CD/ECII and ILSAC GF-1 engine oils. The specification is intended for engines being operated under service conditions expected to generate extremely high engine oil temperatures.

 

[Patman]

Yes, but what EXACTLY does the test entail? What type of conditions does the oil need to pass in order to qualify?

 

[mojo]

It is not just a single test, but a series of tests as you would find in any engine oil specification. There are the physical chemical type tests, the bench tests, and the engine dynamometer tests. For example, this specification (i.e., GM 4718M) requires the oil to pass the Sequence IIIE engine test, the Sequence VE engine test, the High Temperature High Shear Viscosity at 150 C, Filterability, Distillation, Foaming, the Sequence VI engine test for Fuel Efficiency, has a Phosphorus maximum of 0.12%, and Flash Point.

 

[Dick in Falls Church]

Historically, I think that spec appeared just when GM finally accepted that only synthetic oil could solve their design problem in the new Corvettes--and the oil used happened to be Mobil 1.

 

[G-MAN]

Actually, 4718M is only a high temp requirement involving the Sequence IIIE test. It requires less oxidation and volitility on this test than the standard API SL/GF-3 requirements.

(According to Patrick Beddard, Car and Driver, November 2000, quoting Bob Olree of GM Powertrain.)

 

[mojo]

The specification sheet that I have lists all those tests that I quoted above as well as stating that the performance level was SG/CD/ECII and ILSAC GF-1 and not SL/GF-3.

 

[G-MAN]

quote:

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Originally posted by mojo:
The specification sheet that I have lists all those tests that I quoted above as well as stating that the performance level was SG/CD/ECII and ILSAC GF-1 and not SL/GF-3.

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The spec has been udated since it was first introduced for the LT-1 in the Corvette. The spec requires the oil to pass those other tests, which is merely redundancy. The place where the spec exceeds the SL/GF-3 requirements is the Sequence IIIE.

 

[mojo]

Believe my copies of GF-3 and API SL show the Sequence IIIF to be the current test and not the IIIE.

 

[G-MAN]

quote:

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Originally posted by mojo:
Believe my copies of GF-3 and API SL show the Sequence IIIF to be the current test and not the IIIE.

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You are absolutely correct.

Which leads to an interesting question: Can current Corvette oil service requirements be met with a GF-1 oil so long as it meets 4718M? Any 2002 Corvette owners out there? Take a look in your manual and see what it requires and let us know. (One would assume GM would update 4718M to account for new API performance standards.)

At any rate, what I said about redundancy still applies to the spec sheet. The only test sequence requirements that exceeded the API performance standards that were in effect at that time is the Sequence IIIE.