why change oil so often?

are you averaging 150 KM per day? so you need to change oil that often? 

how cheap is your miniral oil?baka naman single grade na mineral oil,but if multi grade naman dun na ako sa change oil every month.

Let's say high detergent MO40 or Multigrade na 40w compared sa Royal purple 20w40.

I usually change my Royal Purple after 3-4months eh i figured na same price lang siya pag 3x change oil na multigrade.

RP has no 20w40 viscosity. either way is fine but there's more waste with the mineral route.

Meron be talaga Full Synthetics? We have already established the fact that synthetic oils are preferred by many motorists than conventional mineral oils. We are also aware of the benefits derived in using synthetic oils. But our next question is: Which Synthetic Oil Should I Use? Is one brand better than the other? What should I look for in buying synthetic oils?
This is a tricky question. There really is not much of an industry standard definition when it comes to synthetic oil, so be careful. The term synthetic has become more generic these days and has more to do with oil quality than it does with the actual oil itself.
Many, if not all synthetic brands have “FULL SYNTHETIC” or “100% SYNTHETIC” or “ALL SYNTHETIC” written on the label but how are you certain that you are buying the right stuff?   It’s just like saying “100% Coffee”. Yes it is, but is it Arabica, Excelsa or Robusta? Or “100% PURE BEEF”… Carabeef or Cow’s beef? Or a blend of the two?

Grades of Oil.
Motor oils are derived from base stocks. That is, a generic oil base is modified with additives to produce a lubricant with the desired properties. A base stock oil with no additives would not perform very well at all. Base stocks are classified by the American Petroleum Institute (API) and fall into one of five categories.
·   Group I and II - these are mineral oils derived from crude oil. (That’s basic. No comment about that.)

·   Group III - this is a highly refined mineral oil made through a process called hydrocracking. In North America this group is considered a     synthetic oil, for marketing purposes. (Hmm. . . quite confusing…... A mineral oil considered as synthetic oil?)

·   Group IV - these are true synthetic oils, known as Polyalphaolefin (PAO).

·   Group V - these are synthetic stocks other than PAO's and include esters and other compounds. (Other compounds???)

Synthetic Base Oils
Currently, there are three main fluids used for synthetic base oil in engine oils:
-  Polyalphaolefins (PAO)
-  Synthetic Esters (Group V)
-  Hydroprocessed Mineral Oil (Remember Group III?)
If you want a true high performance synthetic, you probably want an oil which uses PAO base oil. PAO is the classic synthetic fluid used to make synthetic engine oil and it has excellent low and high temperature properties. The easiest way to verify the use of PAO is to ask the manufacturer for the pour point of their oil. If the pour point is –54°C or lower, then you’ve got a PAO based synthetic oil. Some oils have “PAO” or “polyalfaolefins”  written on the label.
Over the past 25+ years, PAO has been the most popular fluid used for synthetic engine oil. PAO is a pure chemically engineered substance. It starts by chemically reacting pure ethylene (an invisible, explosive gas) into a molecule known as decene (a clear, thin liquid). The decene molecules are then reacted to form a pure molecule known as Polyalphaolefin (PAO). The PAO molecules can be small or large depending on how much decene is reacted. The bigger the PAO molecule, the more viscous it becomes. In the end, you have a pure chemical substance with very strong molecular bonds that resists physical and chemical breakdown. (Now that is synthetic!!!)

PAO is usually combined with a small amount of synthetic ester to provide even greater high temperature durability and improved chemical solubility. Synthetic esters are manufactured by reacting an acid and an alcohol. The reaction products are water and ester. Esters are very stable at extremely high temperatures and are used almost exclusively in jet engines. Unfortunately, full ester engine oils do not work well in automobile engines due to lower operating temperatures and exposure to moisture. If ester is exposed to high moisture at moderate temperatures, it tends to react back into the acid and alcohol. You can imagine what acid in your crankcase would do to your engine.

Hydroprocessed Mineral Oil is a more recent fluid used for synthetic engine oil. This fluid is actually just conventional oil, which has been processed to remove more of the small and large molecules. In the end, the fluid is much more stable at high temperatures and provides good service for high temperature engine operation. Unfortunately, it provides little or no improvement for low temperature operation since it still contains wax. Since this fluid provides good performance at a lower cost than PAO/Ester formulations, it has found its way into the marketplace as synthetic oil. It is somewhat questionable how synthetic this fluid is. (Careful Careful)     (Tsismis.) There are claims that Mobil 1 is not using PAO base oils. (Hehe).

My final recommendation is again . . . careful, careful.

Late in 1997, Castrol changed the formula of its Syntec "full synthetic motor oil", eliminating the polyalphaolefin (PAO) base stock (that's the "synthetic" part, which makes up about 70% by volume of what's in the bottle) and replacing it with a "hydroisomerized" petroleum base stock.