In Reply to: Interesting sidenote, I told Gordon about it last posted by Bill R. on December 14, 2000 at 00:44:14:
week, One of my customers has two 960 volvos that exhibited hard starting when cold. I looked them over and tuned them. Then looked at all the factory service bulletins. It turns out they have a problem with oil deposits on the valve stems and the valves can hang open causing a loss of compression and hard starting. Volvos recomended procedure for this is to put the cars in low gear and drive for 12 minutes at 5 to 6 thousand rpm. Then switch to synthetic oil to keep future valve stem deposits from forming and to remove any leftover. If the factory flat tells you to run synthetic that convinces me there is some merit there.
not blueprint the engine or drive it on the street. Here is the actual story if you want to read it. No Urban myth.
I think it is a matter of personal perference. I agree that synthetics would handle extremes better with less of a propensity to break down.
However,I recall reading a Consumers Report on oil sometime over the last 1-2 years. They blueprinted engines on taxis used in NYC and compared differnet oils including synthetics. Pretty rough driving conditions with 24 hour operations with stop and go with quick accelerations at times. Their finding was that dirt causes wear. If you changed the oil and filter at reasonable intervals (they recommended 5000 miles) you should not have significant wear. They also stated that oils with similar SAE ratings should perform similarly.
Now this must be compared to the Mobil Oil BMW 3series car. Mobil blueprinted the engine, drove the car 1 million miles (not just on the Dyno; they drove it cross country a few times i.e.from NJ to Arizona for a car show as well as around town locally in NJ) and measured the wear after the million miles. They found insignificant, very minimal wear on the engine. Although I do not recall what the oil service interval was, this is a strong argument for synthetics.
I think it does not matter which oil you use and it is a personal perference but the key is to change the oil and filter often, maybe every 3-5000 miles. I use every 5000 miles since it is easier to remember.