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Have you been able to find the 0W-40 in L where you live?
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Not in stores but the Mobile distributors carry them about $5/qt.

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I assume it is Compression (diesel) rated, as well?
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The 0W-40 is only CF rated.

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I have been trying to find DelVac One, but only time I have it was $6.50 a quart ... seems a bit silly at that price.
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You can order from http://www.avlube.com/

$81.39 for a 4-gal case.

I forgot to mention that the number before the W in an oil cannot be looked at in isolation. For example at 40 deg C,

Mobile 1 Tri-Synthetic 5W-30 has a kinetic viscosity of 53.0 cSt;
Mobile 1 Tri-Synthetic 10W-30 has a kinetic viscosity of 59.0 cSt;
Mobile 1 Tri-Synthetic 0W-40 has a kinetic viscosity of 80.3 cSt.

So at 40 deg C, the 0W-40 is considerably thicker than either 5W-30 or 10W-30. API only specified the minimum and maximum value for a particular viscosity so anything in the range is good as far as the standard goes.