In Reply to: How much longer will synthetic.... posted by Brett on September 12, 2000 at 00:15:24:
The weakest synthetic oil is better than the best petroleum oil in all around performance. It is highly recommended to use synthetic oil as shown by the car makers preferred use in their newer cars.
Using a zero weight (0W-**) oil will tremendously help reduce cold start-up damage which tends to be the most likely cause of normal engine failure. The lighter weight oil will begine lubricating much sooner than a heavier oil such as a 20 weight (20W**). After an engine reaches a nominal 100 degree C (212 F) temperature the oil becomes the "upper" number such as **W-30, **W-40, **W-50 anyway.
An upper number of 30 or 40 in synthetic oil is more than sufficient to protect, lubricate and cool a high performance engine, even one that is driven hard or tracked. In fact, a thinner oil such as a 30 weight (upper number) will cool an engine better than a thick oil such as a 50 weight (upper number) oil.
The car makers are allowing 15,000 miles between oil and filter changes using synthetic oil. Some of the synthetic oil makers are suggesting as much as 35,000 miles between oil changes! Many long distance freight carriers are logging over 100,000 miles between oil changes! Personally, I would not allow a personal car to log 15,000 miles beofre changing the oil and filter but your 4,000 mile figure is well within safe limits in my opinion and could be used much longer.
How much longer will synthetic oil last than regular 20w50? Also, somebody here recommended that I use 0w30 synthetic.. is this a good choice? I drive my car somewhat hard, but i want some oil that will last at least 4k miles, if possible. thanks!