Originally Posted By: CATERHAM
Bob I hate to tell you this but you can't compare the KV100 spec's of two widely different oil chemistries without making an adjustment.
The two viscosity spec's to consider are HTHS and the VI.
The 0W-40 has a very much higher 197 VI vs only 162 for the 5W-30 and a somewhat higher HTHSV. The net result of his is that
RL 5W-30 will be heavier than RL 0W-40 at all temp's below about 75C. At room temperature it will be about 25% heavier and more than 50% heavier at 0C. That relative difference will increase as the temp's drop below freezing.
If you wanted to improve the starting performance of the RL 0W-40 you would have been better off simply blending in some RL 0W-30 to produce whatever lower HTHSV you want. The blend will reduce the oil's VI but the reduction in the HTHSV more than compensates for this.
Same oil chemistry for both RL 0w40 and RL 5w30.
Do you disagree with the Widman chart for these?
Bob I hate to tell you this but you can't compare the KV100 spec's of two widely different oil chemistries without making an adjustment.
The two viscosity spec's to consider are HTHS and the VI.
The 0W-40 has a very much higher 197 VI vs only 162 for the 5W-30 and a somewhat higher HTHSV. The net result of his is that
RL 5W-30 will be heavier than RL 0W-40 at all temp's below about 75C. At room temperature it will be about 25% heavier and more than 50% heavier at 0C. That relative difference will increase as the temp's drop below freezing.
If you wanted to improve the starting performance of the RL 0W-40 you would have been better off simply blending in some RL 0W-30 to produce whatever lower HTHSV you want. The blend will reduce the oil's VI but the reduction in the HTHSV more than compensates for this.
Same oil chemistry for both RL 0w40 and RL 5w30.
Do you disagree with the Widman chart for these?