Why doesn't 10W-30 meet dexos1 ?
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Originally Posted By: Nate1979
There is a thread on here showing the dexos spec document. It does have viscosity requirements. 10w-30 is not one of the allowed viscosities.
That's it in a nutshell.
And GM hasn't allowed it as a grade that's permitted to be submitted for approval since about the mid 2000's.
It was before the dexos spec was implemented, and at the tail end of the 2 main specs that GM were applying(GM 6094M, GM 4178M).
It's a prime example of how government policy can skew the direction that corporations are willing to move in.
That's CAFE whether it be good or bad.
There is a thread on here showing the dexos spec document. It does have viscosity requirements. 10w-30 is not one of the allowed viscosities.
That's it in a nutshell.
And GM hasn't allowed it as a grade that's permitted to be submitted for approval since about the mid 2000's.
It was before the dexos spec was implemented, and at the tail end of the 2 main specs that GM were applying(GM 6094M, GM 4178M).
It's a prime example of how government policy can skew the direction that corporations are willing to move in.
That's CAFE whether it be good or bad.
Last edited:
Originally Posted By: Ducman
That's it in a nutshell.
And GM hasn't allowed it as a grade that's permitted to be submitted for approval since about the mid 2000's.
It was before the dexos spec was implemented, and at the tail end of the 2 main specs that GM were applying(GM 6094M, GM 4178M).
It's a prime example of how government policy can skew the direction that corporations are willing to move in.
That's CAFE whether it be good or bad.
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
That's it in a nutshell.
And GM hasn't allowed it as a grade that's permitted to be submitted for approval since about the mid 2000's.
It was before the dexos spec was implemented, and at the tail end of the 2 main specs that GM were applying(GM 6094M, GM 4178M).
It's a prime example of how government policy can skew the direction that corporations are willing to move in.
That's CAFE whether it be good or bad.
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
dexos1 is a one-size-fits-all thing. Since 10W-30 wouldn't fit very cold winters (wouldn't crank below a certain very low temperature), it's not allowed.
For the same one-size-fits-all reason, a lot of people end up running dexos1, which is a synthetic grade, despite not really needing synthetic, which is only needed for certain turbo applications or long OCIs.
For the same one-size-fits-all reason, a lot of people end up running dexos1, which is a synthetic grade, despite not really needing synthetic, which is only needed for certain turbo applications or long OCIs.
Originally Posted By: Merkava_4
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
Both reasons are important. 5w-30 was allowed by GM (and others) up here, at least, fairly early on, with low ambient temperatures. It certainly wasn't a fuel economy issue back then.
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
Both reasons are important. 5w-30 was allowed by GM (and others) up here, at least, fairly early on, with low ambient temperatures. It certainly wasn't a fuel economy issue back then.
Originally Posted By: Merkava_4
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
In addition to other reasons, such as engine design. Consider: the 1st generation Northstar engine (MY 1993-1999) recommended 10W-30. The oil recommendation changed to 5W-30 with the 2nd generation engine (MY 2000+). The 2nd generation engine moved to roller camshaft followers; a GM powertrain engineer told us on a Cadillac forum that the main reason they used 10W-30 in the earlier engines is because it was more shear stable and they wanted that extra bit of headroom on the engines with the direct-acting followers ("bucket followers"). The MY 2000+ engines switched to roller followers and didn't experience as much engine oil shear...so they felt comfortable moving down to 5W-30, as the design allowed.
There's really no reason to use a 10W-30 over a 5W-30 if the engine design allows for it. The 10W-30 grade generally has a numerical advantage in terms of resistance to shear, but if this is never realized in the field, then it's mostly a moot point.
So you're thinking GM moved to 5W-30 for fuel mileage reasons instead of cold startup protection ?
In addition to other reasons, such as engine design. Consider: the 1st generation Northstar engine (MY 1993-1999) recommended 10W-30. The oil recommendation changed to 5W-30 with the 2nd generation engine (MY 2000+). The 2nd generation engine moved to roller camshaft followers; a GM powertrain engineer told us on a Cadillac forum that the main reason they used 10W-30 in the earlier engines is because it was more shear stable and they wanted that extra bit of headroom on the engines with the direct-acting followers ("bucket followers"). The MY 2000+ engines switched to roller followers and didn't experience as much engine oil shear...so they felt comfortable moving down to 5W-30, as the design allowed.
There's really no reason to use a 10W-30 over a 5W-30 if the engine design allows for it. The 10W-30 grade generally has a numerical advantage in terms of resistance to shear, but if this is never realized in the field, then it's mostly a moot point.
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