Now or in the future..................................? I hear a lot of 5W oils flow better than 0W oils at low temps. So everytime i look at a Group III "0W" (Mobil 1) vs a Group V synthetic (Redline, mail order) or Group IV (Royal Purple, API SL, off the shelf,) I ask myself how much im losing on the 0W. And yes, GC is a thick 30 that is still a 0W. So, is either ok? Or is synthetic vs. conventional, or even basestocks, an issue here with below-zero and or cold-weather flow and lubrication performance? Id be most confused as to whether to seek out a 0W-20 or 5W-20 for this 1991 Civic CRX Si im picking up. High mileage runs fine like most all CRXs... 3.75 Qts of oil lol thats 4 quarts Was going with Castrol Edge for that one. Tossed around the idea of putting RP 5W-230 in there to. At 4 quarts i can spend whatever i need to on a good oil and simple PureOne filter for it. Going with 20, not 30.