Synthetic Oil Field Test Update.
 

I started at 75K miles, changed both oil and filter with AMSOIL filter and 0W30 Synthetic blend, the recommend oil by AMSOIL for my truck. Now, at 80K, my DIC is giving me the "Change Engine Oil" signal. At, BTW, precisely the interval which it used to kick on for CONVENTIONAL oil changes.

Am I supposed to just ignore this signal from my engine and continue to go the 15,000 -to-25,000 mile/"once a year" interval without a change, that the synthetics brag they provide?

I know to many, this is probably just going to be seen as another "which is better" bash thread, but IMO it goes right to the heart of the issue...

..which is: Is Synthetic oil really worth the added expense? Are extended oil change intervals really safe for our engines?

Is it possible it may take a oil change or 2 to get all the old oil out of the engine? I read a post that snowjay put up in the Tahoe/Suburban section about the oil life monitor. He had a link that sent you to another forum. I read it, and had a new found respect for the OLM, it doesn't sense conventional or non-conventional oils, it just checks the oil for how well it lubes the engine. Personally, on a gas motor, I would not go by what AMSOIL says, I listen to my truck. Against what financial ANALysts say, my truck is an investment, not a purchase, and when my truck hollers at me I listen. I dont want to make an opinion on whether or not Synthetic is worth the expense just yet. i haven't made an opinion for myself yet.

https://chevroletforum.com/forum/tahoe-suburban-25/oil-life-monitor-28457/ That should be the link to the OLM post

I've been running Amsoil in my 5.3 since it had about 40,000 miles.(when I bought it) I change every 10 to 15k but I change filters at the OLM alert and reset it. I now have about 130k on the truck and it uses no oil between filter changes. The only issue with the engine has been the piston slap on cold start and that has been consistant through out the time I've owned it. I tow a 5600# camper with it a couple of thousand miles a year and the rest is local runs of 8 miles or more.

Bob

There is know way it can know what type of oil is in it. The OLM uses a algorithm that bases it off your driving. If you are using a Amsoil filter (and you truly believe in Amsoil) then reset the monitor and keep driving.

^^^ exactly. The OLM is monitoring the engine for rpm, temp, oil pressure, throttle position, etc and modifying the variables that go into a calculation that predicts when the oil should be changed according to the engineers that designed the program. It has nothing at all to do with the actual condition of the oil. Testing the oil is the only way to confirm that the oil is still doing it's job. I've not seen a report yet that says the major synthetic oil brands require replacement at 3,000 to 5,000 mile intervals like people seem to think are gospel. When I ran Amsoil I tested it at 10,000 miles and the test indicated i could go another 3,000 miles before retesting. I tested Mobil 1 and received similar results. I run 10,000 mile synthetic oil changes and filters at 5,000.

So, general consensus is that the OLM is for non-synthetic oil, but it would probably still be wise to change the filter every 5K or so.

I can live with that.

MDTahoe, I can't say I do believe in AMSOIL. I always believed my OLM system sensed some type of acidic or corrosive condition in my oil, however. I do tend to be a little tentative when trying something new.

Do you believe in God? Carefully watch a pious group of church-goers leaving the parking lot after Sunday Worship service, and see what you believe in then.

So at 82K I installed a new K&N oil filter, reset the OLM, and topped it off with oil. I'm going to 88K, and see what develops.

The important point here for synthetic oil users is the OLM isn't monitoring the actual condition of the oil, just alerting the vehicle user to the standard safe oil change interval, in the event they were using non-synthetic oil.