just because the oil looks clean doesnt mean it is. taken from some literature: it still contains contaminants, sludge, and the additives are broken down. it can also cause variable valve trains to malfuntion. and that short trips where the car never warms up without frequent oil changes is really bad. it does stat that cars that are driven primarily on the highway can go up to 7500 mile before an oil change
As for oil cleanliness, looks have nothing to do with it. Oil has additive packages to deal with the contaminants. Oils in different markets are even different colors from the standard "golden honey" of the US market. The ONLY way to say it is good or not is by using an oil analysis.
Simplest test is to feel it between your fingers - any contaminants are removed by the filter DUH! If it doesn't feel slippery then is it probably worn out and needs changing. It's just oil not Rocket Science!
Anything that is so small to pass through the filter is not going to be a problem in the engine UNLESS you have something really weird going on like lots of acid forming water. Engines would fail a lot more frequently if engines needed extreemly clean oil to operate. The simplest thing you can do to improve filtering is to add some Neo Magnets to the outside of the oil filter to trap microscopic steel particles . . . sludge is the oil breaking down and is soft - if you have sludge you are not running hot enough and water is building up in the oil or are running too hot breaking down the oil and your oil is due for a change.
The easiest indication of oil needing changing is the mileage dropping which can happen in 5k miles or 8k miles.
I would be more concerned about running 0w20 oil in your engines than anything else. Oil that light is going to break down its protective film under load on lifters and cam chains where there is extreem contact pressure. Although you will see better mileage from reduced oil drag on the pistons and easier oil flow through the oil pump and filter it will not protect enough in other areas of high loads.
Well for years (about 15)i was strictly using Castrol Oil and changing it every 3000 miles.
I began to read up on it for my motorcycle, a 2004 CBR600RR, and learned quite a bit.
First i learned there are as many opinions on oil as there are *** holes in this world so its hard to just search y'old net. A lot of info based on nothing but what they have heard. I will say that a motorcycle uses a wet clutch which generates quite a bit of heat, and redlines high, mine is 15K. So, for references i looked for data from motorcycle racers that ride hard and open engines on a regular basis.
Well what i came up with was using 5w-40 Shell Rotella-T Synthetic oil, i get it from Wal-Mart for around $18 a gallon. I change every 5k now which is probably still to early but its hard to get away from that 3k Ive been doing for years. My truck has 202k my civic has 215k and my Chevy Venture has 124K. Synthetic is so thin and seems to coat things better. I don't get that start up tick any more. I'm sold on it.
Do a search for the Rotella-T Synthetic and you'll find a bunch of stuff.
So this is just my opinion and it works for me. I really wish there was new oil data and tests out to view. It seems most tests are old or bias.
Gas?? Oh you mean the expensive smelly stuff Grandpa used to power his car with? Silly old Man.
Hopefully somebody can confirm this, I've read it once.
Synthetics also differ from dinos in how the multi-viscosities are reached. A 5w-30 dino is a 5 weight with modifiers added that let it act as 30 at 100C. The synthetic is reversed. It's a 30 weight oil with stuff added that let it act as a 5 at ambient temps. This is why you can have a 0w synthetic and not a dino.