Yes, it is a vast right-wing conspiracy, and we would have gotten away with it too were it not for you meddling kids!

Well, now that the big scam is blown, I guess I can contact all of my fellow shadow-men in the big oil companies and tell them to remove things like this from their websites:

http://www.valvoline.com/carcare/art...cid=2&scccid=2
"The multigrade oils' viscosity modifiers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss. Permanent viscosity loss occurred when high shear forces (such as the relationship between the main bearings and the crankshaft) actually break the polymer molecules into less-effective smaller pieces. On a similar note, temporary viscosity loss also occurred when the polymer molecules aligned themselves in order to create a path of least resistance.

Fortunately, today's additive packages have improved oil's shear-resistance. However, oils with the same rating from different manufacturers can exhibit different viscosity ratings in an operating engine, depending on the shear stability of their viscosity-modifying additives.

Singlegrade oils will become obsolete for performance engines in the future. We dropped SAE 30 and SAE 40 because SAE 10W40 does everything 30 or 40 can do—and some things the straight grades can't do—like increasing horsepower. If an off-roader doesn't like 10W40, then use 20W50. It can do everything a 10W40 can do except pass the sub-zero viscosity test at -20 degrees C."

Dang, Dick Cheney is gonna be really pissed that I let it slip out that it is all made up. I guess I can forget about my hoped-for nomination to the uber "they / them" committee. :(

Interesting read. 20w50 ftw.

Eh I change my oil every 2,000-2,500 miles....20w50 in summer/spring, 10w30 in winter/fall. Running no omp...Castoral GTX. Mainly because in the summer my oil temps are usually always in the 200+ range.

EDIT: I wish they could have gotten the ash and zinc numbers for mobil 1 and redline...my friends all run mobil 1, but I change my oil religiously :D Too bad they didn't add royal purple to the comparison too..that seems to be popular.

The real way to consider what oil you should use, is whats recommended by the manufacturer and use the Temperature Chart in the owners manual as a reference. There are way too many people who get the wrong concept here because of the word of mouth. Learn it from the mechanics and Rotary specialists. Maybe take an auto class and you can learn a lot and you might even find yourself in the auto program and get certified like me. You really do learn how much people do things wrong. Again, look at the temperature chart in the owners manual or repair manual. Most will fall in the 10w-40 range for colder temps and 20w-50 for the hotter temps. These are also the weights Mazda, Racing Beat, Mazdatrix, etc. all recommend.

Interesting stuff here... I think I vary between 10w30 and 20w50... but I'll have to be more conscious of what I use now.

Most people confuse the first number for weight as the w stands for winter starting temps. 5w-30 and 10w-30 have the same weight. Most racers use 50 weight because it is thicker and creates a better cushon for the bearings to float on, too thin of oil will cause rubbing and friction.
It is true that engines have limits depending on how tight they are. I would not run 50 in a newer car, but for the old rotary, no problem. 15w-40 is my favorite.