Great objective synthetic oil info here (NOT selling anything!)

[the_sarge]

This gives a thorough analysis of synthetic oil performance. It's a long read--grab yourself a cold beverage and read on! http://neptune.spacebears.com/....html

[Mr. Poopypants]

I was reading it, interesting stuff, but they just stopped. They did the first few parts of a test and just left it hanging.They also said at the end, instead of contiuing this test, they are going to do an oil test that is not as mileage dependent....but that is the main concern with oil, quality over mileage.

[the_sarge]

It takes a bit of digging to find the Mobil 1 and Amsoil test results. They tested each oil for a year. Here are the links.http://neptune.spacebears.com/....htmlh ... m/....html

[Mr. Poopypants]

Oh, It seemed like the test just dropped off the face of the earth.Thanks!!Wow, I am impressed with the Mobil1 results. Good to know that I have been using it since I bought the Vibe.

[Psychobroker]

Wow, excellent study! Thanks for the link! However, I'm now concerned about my use of AMSoil vs. M1...I change my oil and filter (AMSoil too) every 10k miles, so this part of their AMSoil study disturbs me:Quote »Mile 8000 -- Bryan Savage, May 1, 2004.Oil/Vehicle miles: 8,130 / 39,106Oil added after sample: noneA road trip caused us to miss our sample by a hair over 100 miles. At this point the oil looks black, like used oil ought to. It also continues to thicken up, and is now officially a 5W40 oil instead of the 5W30 we poured in there. Frankly, this annoys the heck out of us -- if we wanted a 40 weight oil in there, we would have bought a 40 weight oil -- and we would have quit right here, except it's not worth the din of hate mail we'd get. So, we'll see what happens, particularly whether TBN manages to rally, 'cause at the moment it's dropping like an acid eater. Wear, however, continues to be for all practical purposes inconsequential. A good oil, yes, but a long-termer? We'll see.Mile 11,000 -- Bryan Savage, September 17, 2004.Oil/Vehicle miles: 11,024 / 42,000Oil added after sample: 1/2 quartToo much good weather eating into car-driving time. Well, motorcycle season will be up in a few weeks -- it's already dipping into the 40s overnight -- so mileage on the test car will increase. Still, expect the study to reach its one-year mark around 13,000 miles instead of the 18,000 miles that Mobil 1 saw.Amsoil continues to impress with its wear metals but the viscosity is really getting out of hand. TBN is back down again as well -- the effects of make-up oil on its longevity are particularly evident in the last few samples. Frankly, with the viscosity/TBN issues, we are suspicious that Amsoil's wear metals are simply a byproduct of an older engine. A re-test with Mobil 1 is probably in order.Mile 12,000 -- Bryan Savage, October 15, 2004.Oil/Vehicle miles: 12,046 / 43,022Oil added after sample: 1/2 quartIt's that time of year you've all been waiting for: when the economy of motorcycling is outweighed by the lack of mercury in the thermometer. Rats! Well, this oil has about another month to go before the one-year mark is up, so we figure the next sample will be the last. So far so good though; Amsoil is holding its own, except for viscosity. We've noted about about a 17% drop in fuel economy and we're curious to see whether we pick that back up with the next brand of oil.The results continued Amsoil's trend of excellent contamination control -- wear metals are low, insolubles are still under control (remember, by this time Mobil 1 got its oil filter changed from too many insolubles), if only viscosity weren't so high! This stuff, which says 5W30 on the bottle, is now a middle 40 and is oozing its way toward 50**! Bad news for engines that prefer thinner oil. Any connection to the fuel economy drop? You'll know as soon as we do.I guess if I poured in some "make up oil" around 7k-8k miles, things would look better, but I've never had to. I have never noticed any significant oil consumption...has anyone else? This is on a 2zz, of course, so 1zz's may behave differently...thoughts?**This concerns me! Does the 2zz "prefer" a thinner or thicker viscosity?

[Psychobroker]

Quote »Mile 14,000 -- (removed) Brewster, December 2, 2004.Oil/Vehicle miles: 13,994 / 44,970Oil added after sample: noneThis is it. Amsoil is done! The oil exceeded a year in service, with 14,000 miles on the ticker, and no filter change! Well, if the year hadn't ended, we would have had to change the filter now -- it finally reached our insolubles cap, 2,000 miles after Mobil 1. The main thing that stands out on this, our final Amsoil sample, is the ridiculous viscosity. This 5W30 oil has now thickened out to a 15W40 -- argue whether it matters if you like, but we believe engine builders spec an oil for a reason, and this oil is far, far thicker now than intended for the LS1. Switching to our flush Mobil 1 netted a nearly instant 10% improvement in fuel economy, and the engine runs a heckuva lot smoother too. To Amsoil's credit, wear metals remain in check, but we will soon see whether that was really thanks to the oil or just to engine break-in. We'll start posting detailed analysis in the coming weeks.Ok, at this point (~13k miles) AMSoil's insolubles level is better than M1's, but the viscosity much higher -- not good . Perhaps changing every 8k would be best if I decide to continue with AMSoil.

[olympic]

9 times out of 10 Amsoil will substantially thicken with use. I had it happen in my 03 Vibe even with a dual remote bypass. It was well into the 40 weight range by 7000 miles. But it has yet to be shown that the thickening hurts performance. Wear numbers remain very low. Personally I wouldn't leave it in much past a mid 40 weight or around 14cst. 8k may be about right.