The bottom line is wear numbers. That's pretty easily analyzed. It's what I base my suggestions on.
What your saying is true, but you have to realize that engine don't operate only between the spec ranges for oil. You also have to realize that those spec ranges are for *new* oil. Not oil that's just been run for 7,000 miles.
Too, manufacturer in recommending oil are looking out for their interests, not necessarily *your* interests. While any manufacture that is not taking your best to heart is not going to remain in business (or flourish), you also have to realize that they are going to do what makes sense for them. It's a compromise.
The best way do decide what oil works for you is to run a couple different grades and do an oil analysis on each. Pick the one that give you the least amount of wear. Because once you've worn away metal, there is nothing you can do to put it back. So minimizing how much metal you pull out of the engine with each oil change is the only way to go.
That is not going to happen with 5w20 oil. Which is where manufacturers hear are heading to shave off a mile per gallon (and more) to meet overall epa regs across a couple million cars.
In europe and other parts of the world where they worry more about engine wear, they recommend much thicker oil than they do here. More along the lines of what they've been putting in engines since the early 20s.
While technology has advanced, the basic laws of physics haven't changed. Probably the biggest threat to oil in toyota engines is that they have hot spots and they tend to shear the oil pretty well too.
For example, if you don't change your oil properly on the v-6 engines you
have a major headache on your hands because the oil will gunk up on you.
When selecting oil you have to look at the minimum and maximum ranges you'll see. For above 50 degees minimum, 20w oil if perfectly fine. As I mentioned with synthetic, it's less of a difference because the oil is more stable from low to high - even without additives. Plus they use much better (and more) additives so the performance is all that much better for all that much longer.
But you can certainly get great performance from syn mix oils as long as the additives are top notch. Short of good base stock, the quality of the additives are hugely important.
Alan
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Originally Posted by ekunst
The first number in the oil designation, before the "W", ie 5W-40, is the "winter weight" of the oil and it directly correlates to the oils viscosity "cold" or at start-up. (the lower the "W", the easier an oil will pour or flow.) The winter weight number has little to do with the viscosity of the oil when it is fully warmed up. The second number (-40) reflects the "operating temperature" viscosity which represents the oils ability to resist "shearing" when squeezed thru a small oirfice or bearing journal.
regardless of hot or cold climate, it is always an advantage to have a motor oil with a lower "W" weight because this oil will flow with greater ease to the vital parts at the top end of the engine. this characteristic is also crucial to start up lubrication in most if not all engine made today, as the tolerance of moving parts in the valvetrain and the like are very small and lack of oil will most definitely shorten their life. this is another reason why 5w type oil is recommended by the manufacturers. additionally if you live in the northeast, like me, you definitely notice the difference lower winter weight oil makes when it is cold out and the engine strains to turn over.
so if you live where the morning temps get down below 40 F, you may reconsider using that 20w or 15w weight oil. you may be damaging that expensive-to-repair motor at every cold start-up. just some food for though...  |