I'm looking into this. If your correct I'll say so. But I've seen many oil analysis reports on oils used 12,000 plus miles. I have never seen a notation of 'its thicker'. Maybe really used oxidised oil with depleted additives. Sheared and "thinner" is more the norm and occurs first. The Hemi is very easy on oils. The ADDITIVE pack is the main reason that oils designed for extended drain last so long. Once the additive pack is used up then oxidation occurs. That will make oil thicker. Its used up. Its not the 'thickness' that extends motor oil life. The manufacture has said oil change interval on the 5.7 Hemi is 8,000 on non-synthetic!

 

Honestly, I thought this was pretty common knowledge. Has been discussed a good bit from time to time in the 2nd, 3rd Gen and Dakota sections as well as a host of other forums. Someone even posted a letter straight from an Amsoil engineer when he questioned it that confirmed it at one time somewhere on this forum - I'm sure a search will pull it up. The engineer basically stated it as a positive trait but also admitted that it's the only way to make the product last so long.

I have NO PROBLEM with their products and have used them myself. When I was tourney bass fishing, it was the ONLY lubricant that went into my outboards. My issue is when using it for extended periods in very viscosity specific engines.

A quick excerpt from the first of about 10 analysis articles that came up in a search:

By rights it should be the absolute last sample, but we're going to spot Amsoil one more after this. At 13,000 miles, Amsoil continues to hold steady -- clearly, Amsoil can last much longer than we initially thought possible. That is provided, of course, that you have no problem with the oil thickening way out of grade (many people don't, which is why we continued the test despite our own reservations about it now being a solid 40-weight oil). Well, one more sample to go, and then we'll enter the next flush period, which should settle whether the oil is contributing to the fuel economy drop.

This 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.

 

So far on the oil site they are saying NO this isn't how oil,any oil works. That shearing,thinning is a bigger issue. That thickening occurs when additives are used up and oxidation is occurring. The ONLY time I've ever heard of this on any forums about oil or Amoil is here by you. I'm waiting on more replies to the question. Amsoil is widely used by the diesel crowd with bypass filtration. Many oil analysis over the years has been discussed and posted. The subject of thickening has never been mentioned or discussed. Only time I've ever heard of such I already stated. I 'm not defending Amsoil. No need to defend Amsoil products with the world wide reputation they have. The fact is 3,4,5,6 thousand mile oil changes are of the past with many of the oils and filters that are out there these days. As I already stated the vehicle manufacture has said the Hemi is now at 8,000 mile oil changes using NON synthetic. I just read that the new oil change schedule is going to be 15,000 on the 6.7 Cummins in Dodge trucks in the coming future.

 

I read the same article poster by HammerZ71, and I've also read other reports of Amsoil oil thickening over time. Part of it is that certain Amsoil products start out on the "thick" side of the original viscosity spec so even a moderate amount of thickening will take the oil up a grade. Over time, vaporization and oxidation contribute to oil thickening.

I have nothing against Amsoil products, and I've used them with confidence in the past. An independent mechanic who worked on my BMW 740 used Amsoil exclusively in his racing BMW (with large dry sump) and said he noticed reduced operating temperature with it and lower wear.

On some sites, BITOG for example, there are numerous reports and UOA showing that some Amsoil oils thicken over time. I agree with Hammer's point that the Hemi MDS system requires a very specific oil viscosity to operate properly.

 

The thickening is when its past its useful life. All oils do this. Not just Amsoil.

 

Not all oil companies claim 25,000 mile oil changes. Your comment is that the oil thickens when the oil is past its useful life. If a UOA shows Amsoil oil thickening out of grade at 10,000 miles then does that mean its past its useful life?

I'm not questioning the quality of Amsoil products. I believe they are very good products and I've used them in the past. But I question the 25,000 mile oil change claim...when UOA show oil thickening at less than half that.

 

It very well could be. Amsoil and others that have and market high mileage oils don't "guarantee" that they will go 15k or 25k in certain conditions or applications. There are many high mileage oils on the market that advertise high mileage capability'. That also state that certain conditions and criteria be met to obtain those high mileage results.

 

i've read a few results that shown amsoil to be way over viscosity well under their claimed change time. i have also read this a long time before i was on this forum. there was a thread on it that got locked and i think deleted on DT not too long ago because the amsoil lovers got all pissed off even though the op didnt bad mouth amsoil just warned against leaving it in too long.

among us guys who professionally wrench its pretty well known that these long life oils thicken up the longer you leave them in.

 

Our personal family vehicles are a 2002 Dakota with a 4.7 V8, it has 200K+ miles on it, I also have a 2001 Dodge Caravan with a 3.3 V6, it has 300K+ miles on it. Both receive my personal attention when it comes to changing the oil/filter. They both get a OEM/Mopar Filter and 5W30 Castrol GTX every 3 to 4K miles, neither one uses any oil and knock on wood both show no signs of giving up anytime soon.

Now for my 2 stroke powered play toy's I've found the benefits of using a good synthetic oil justifys the additional cost.

 

Ok.So? Your wasting money and a valuable resource. OIL. Are you not changing oil more often then the manufacture calls for? I have run 3 vehicles 250,000 on 20,000 plus mile oil changes using synthetics(Amsoil) and filter changes and oil top off every 7500 miles with no engine related issues. My Corvette is at 58% left on the oil life monitor and its been 6100 miles on the standard Mobil 1 that is called for. ( I am going to Amsoil XL 5w30 next service) I have a lady friend with a 2006 Colbalt with over 180,000 going through downtown Atlanta stop and go traffic 88 miles round trip twice daily. She goes by the oil life monitor and go's to a Quick lube when it hits 0. Gets their what ever oil and filter. It runs great and gets great fuel mileage. I looked in the oil cap of it and nothing. Looks new in there. Hardly even any varnish. GM says to follow the OLM using the proper oil. Many manufactures are pushing the same. That's what she and thousands do with long engine life. Point is we all have these storeys. It took me forever to wean off 3 to 4 thousand mile oil service. As hard as quiting smoking. Its not needed any more. Hasn't been for quite some time. You are wasting money and oil. The other point of this post/thread that its NOT only Amsoil that 'thickens' over miles and time. Which I have never really heard of or seen on oil analysis that have been posted on the oil forum. The few times I used a oil analysis at lets say 12,000 plus miles it did not indicate that. You really want to know what your engine an oil is doing? Any fliud really. Gear oil,trans etc. Here you go. http://www.blackstone-labs.com/