5% oil life left

… especially when you consider that the OP’s Cadillac Owner’s Manual clearly specifies the synthetic oil that he is wondering about, and also explains the meaning and function of the OLM.

They built a 20% margin into the algorithm according to some detailed info I read a few years back by some guy involved in the development.

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The CT6 Owners manual also says to check oil level every 400 miles. It’s a beautiful car, and deserves to be well looked after.

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The problem I have with OLMs is this. Even though an oil sample may test fine that does not guarantee that the engine is not building up sludge, coking oil, or seizing oil control rings on the pistons. There are many other factors besides miles and time.

How many people post on this forum about their engines being low or run out of motor oil? Many. What happens to the remaining motor oil on say a 5 quart capacity engine when it’s being run 1 to 2 quarts low all the time? They’re down 20 to 40% of total capacity and that remaining 60 to 80% of motor oil is going to take a real beating due to the oil temperature running much higher than normal.


With that and changing the oil at 50% oil life out of fear, the drain oil should be better than the oil we used 25 years ago (when we had sludge issues).

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It looks like you conflated olm and oil testing. Oil testing will reveal condition of oil and other contaminant levels that indicate if sludging is going on. And most olm don’t just use time and miles, especially the gm algorithm discussed above.

That has nothing to do with olm. That is just owner neglect plain and simple. People not checking oil between changes. Most people cite mileage saying something like I had my last oil change 5000 miles ago and this time it was down 3 quarts…

I can’t figure out the Dexos thing. There are Full synthetics that don/t have the Dexos symbol on them and there are synthetic blends that do have the symbol.
Does that mean that some blends are better than some some full synthetics or is it a matter of licensing fees.

Ding ding ding, give that man a ceegar!


Since the talk has gone into the neighborhood of “excessive thrift " Tom or Ray used to say " It’s the cheapskate who pays the most.” I used to have a definite idea of what other people should do.

I remember on another thread, about a Honda Civic which was specified to use 0W20 oil, the OP was asking if it requires synthetic oil, since the manual did not specifically say that. I am sure one could get away with using 5W20 mineral oil, as long as they change it at a reasonable interval. Even 5W30 would probably work fine.

I think a lot of these really thin viscosity oils are being specified for EPA fuel economy reasons, and a slightly thicker conventional oil could actually provide better protection for the engine. Some models specify such oils when sold in foreign markets–with the same exact engine that specifies a 0W oil here.

OK4450 raises a good point.

OLMs assume the oil levels are up in the acceptable range, (like between full and down to the “add oil” line).

If oil levels get below the “add line”, especially for any length of time, then the oil will run hotter, which shortens its life.

Are there any OLMs out there that factor the oil level into their oil life computations?

On what do you base this assurance? Gut instinct? Years in the industry? Many years spent rebuilding engines knowing what oil was actually used in them?

The oil may have been specified for EPA mileage but the engine was designed with the tight clearances that allows the use of this oil. Thicker oil may increase the wear and tear on the engine, especially at startup.

Second guessing the folks that actually designed it, tested it and then measured the wear afterwards is not advisable.


And you know this? How? Dangerous advice in my opinion.


There seeems to be no shortage of low oil complaints on this board or shortage of complaints from people carping about their 2 year old/25k miles car going through a quart of oil every 800/1000/pick a number miles. Not to mention innumerable sludge complaints which are generally related. Unless these people are all lying crackpots…

Oil temps in my Lincoln are kept down to some degree by the oil filter adapter which routes engine coolant through the adapter and removes heat from the oil. Some cars in the past (SAAB) used an external oil cooler on their turbochraged models.

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I have to take some responsibility for this, because I made an error, apparently. The comment was flagged (rightly) and I clicked to delete it and (I thought) the two replies at the time. Instead it left the replies. I am deleting them, because even the remnants get people going.

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I’m sure you have synthetic oil you can go 7,000 miles if you are not going on a trip weight till then the dealer is all about money

In the persons original post they say that the shop is always trying to get them use synthetic fluids . That may mean they are not using synthetic but we don’t know that. Also the vehicle manual may have a different mileage figure than the 7000 you post.

So if the manual said “every 12 mos or 10,000 miles” would you change it at 8 months of 7,000 miles?

Many newer cars monitor engine conditions to measure oil life (Our 2011 odyssey has the same system.) If you look in the manual, it doesn’t give a range, it simply says to change the oil when the computer tells you to.

I don’t think @nybob6 is trying to save a few bucks, he’s just hoping to wait until he feels safer going to get it changed. I agree with @Mustangman - don’t over think it. If you’re only going to the grocery store once a week you can probably wait a while to change the oil. It’s not like the oil doesn’t protect at all once you hit ‘0,’ it’s just time to change it, not unlike changing the oil at 6050 miles instead of 6000.

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Right at the top it says Cadillac CT6

As for your other comments, I profoundly disagree with you . . . but I don’t wish to discuss it, either

What are you doing . . . ?!