In Reply to: Re: How much longer will synthetic.... posted by Bob ///M3 on September 12, 2000 at 07:07:29:
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!
If you recall, When I bought the car, i was using 1 at /1200 miles...At about 3K miles, I switched to synthetic (mobil1 5w-30), and I continued to consume at the same rate...At 7K, I switched back to conventional, which I've used since...I'm now at 18K miles, and about due for my INspection I. I plan to have the dealer switch me back to BMW branded synthetic.
I'm thinking about keeping that synthetic in for the entire duration between lighted service intervals, or , about 10K miles. All synthetic mfgs will tell you their oil is easily able to last far beyond that...Now, consider that i'm now using about 1 qt / 2K miles...So, even though I may go 10K miles between changes, that includes approx 5 new qts over the period. In addition, I'm thinking about changing just the filter every 5K miles. I believe that this regimen should protect the engine very well.