VetteDrmr

My wife and I recently completed a long west coast road trip in our '14 M7 'vette. When I was getting ready to leave the oil life monitor showed about 60% life remaining. I always run Mobil 1, and have my oil analyzed by Blackstone Labs. I think the OLM is a good tool to have, but it is only a tool. It is not a bomb timer (where when it gets to 0 the engine goes boom!), nor is it some kind of conspiracy implement between GM and the oil industry. So, I decided not to preemptively change the oil, but run it through the trip and see what the analysis said.

So, after a bit over 5,500 miles on the trip, and 11,xxx miles on this oil change, here's the oil analysis. OLM showed roughly a 140% usage, but the engine (which clicked over 100K miles on the trip), came through with flying colors.

In summary, if you're using a full synthetic oil, IMO you can easily go 7,500 miles between oil changes. If the OLM times out, just reset the thing. Or change the oil, it's not that expensive. But changing the oil every 3,000 miles is just a waste of time, money, and resources.

Y'all have a good one,
Mike

dbdave

Finally, an oil thread with nothing but common sense! Thanks for that!

Bomb timer.

Patman

Thanks for posting this UOA Mike! I wish more people on here would get this done and post them. (FWIW I have been getting UOAs done on all of my vehicles since about 2002) It's too bad you didn't get a TBN here, as it would've been nice to see that value at 11k. One area of slight concern though is the fact that the iron level at 11k was almost double that compared to your previous interval with 7k on the oil. So it's possible that you were getting a bit more engine wear overall by running that longer interval. At the same time, UOAs are not always a perfectly accurate way of determining true engine wear, they are more valuable in determining the condition of the oil itself.

One thing I have learned myself from doing UOAs are that 3000 mile oil changes are definitely a waste of money (with the exception of the fact that C7 owners still need to change their oil once a year while under warranty, so many on here might hit the 1 year mark around or even before they hit 3000 miles) But I wouldn't take Blackstone's advice and go to 13k though, I find that advice from them a little foolhardy considering they don't even know what the TBN was on this interval. It could have been below 2, so you definitely wouldn't have wanted to push it any further.

PS-it's also very cool to see a C7 with over 100k on it, I believe you're the first one on here to achieve that milestone

owc6

I am at 0%.

Last week it was 4% and I said I would get it changed this week, but life got it the way. I'm not worried about a percent or two on either side of 0.


Keep in mind, that both the OP and I have no real original warranty to worry about. Before this, I would not let it get below zero, but ONLY FOR CYA. That ship has sailed for me, but it may be something someone with an active factory warranty may want to consider (and not let it get to/below zero).

NmtMev

I like it!

I would use the side of caution on a forced induction car however. my experience with Mobil1 and boost is I'm at a 20w already at 3000 miles. lots of fuel dilution. 3 cars and 10 years later it's the same story.

For an N/A car your results are very good.

pewter99

not something I would do on a regular basis but I always ran my C5 and now my C6Z down to the teens or even single digits before changing the oil. Only time I didn't was if I was at 30% or less before a big trip partly because it was normal beforehand maintenance and partly because I didn't want to have to deal with it right after getting home.

NmtMev

and just fyi... Blackstone calculates fuel dilution using the 100* vis cst. as long as the Vis is in line then they report <0.05. however that is not exactly correct. They did not use a GC to analyze the fuel dilution. Also as someone said above ask for TBN next time. I'm surprised they didn't recommend that on the report.

VetteDrmr

In normal conditions I run to around 10% OLM values, mainly because that's when the system starts telling me it's about time, then I get around to it in the near future. I'm not worried about TBN values, mainly because I've had them analyzed before and learned that, if you stick with the OLM monitor (on my C5), the TBN values are in good shape. This was just an opportunity to see how a full synthetic oil would work in a modern engine when the mileage was pushed a bit beyond normal change intervals.

I agree that they tend to be a bit aggressive on their recommendations, but their chemical analysis has always been consistent. The main experience I've had has been with my C5 (280k+ miles and counting), and the wear trends took a bit of a step up a while back. As a result I now change the oil on that car when the OLM gets to 30%, and the wear rates came right back down.

Thanks. We bought her with 83K miles on the Odo in April '17, but we've been enjoying her a lot since then.

Have a good one,
Mike

Patman

You are partially right here, Blackstone does not use gas chromatography to figure out the true fuel dilution. But it's not the viscosity that they use to determine it, they look at the flashpoint instead. It's an approximate guess, because as you get more fuel into the oil the flashpoint does go down, but it's definitely not as accurate as gas chromatography. The lab that I use (Wearcheck Canada) uses GC (ASTM D3524) to determine the true fuel dilution.

Viscosity would never be a proper way to determine fuel dilution, because oils will thin out just due to normal shearing of the viscosity index improvers in it, even if no fuel is present in the oil.

VetteDrmr

This reminded me of something I read one time that I was curious about. For the purposes of what I understand and read, I'll refer to the format:

XXw-YY (e.g. 10w-30).

As I understand it, traditional oils have a base viscosity that is XX, and modifiers are added to make the oil viscosity higher at elevated temps (YY).

As I read, synthetic oils have a base viscosity that is YY, and modifiers are added to make the oil viscosity lower at cold temps (XX).

Is that true?

TIA, and have a good one,
Mike

Patman

It's not really as simple as that, as it all depends on what base stock is used to begin with. A true synthetic oil that uses a PAO and ester base in it's mix will naturally flow very well in the cold, so they might need little or nothing added in order to qualify as a 5w, and also won't need too much in the way of viscosity index improvers in order to reach the top end viscosity (30 weight for example). A synthetic that uses a group 3 hydrocracked base stock isn't going to have those same characteristics so it'll need more modifiers/VII in order to be a multigrade oil. Then there is a new player to the table in recent years, a GTL base (derived from natural gas) and it mimicks the behavior of a true PAO base stock very closely, even though it's classified more of a group 3 (some refer to it as group 3+) So there could be a few different ways that an oil is formulated, that's why when people say "oil is oil, it's all the same", I beg to differ.

LIStingray

Mike - it would have been really interesting if you hade started the Blackstone oil analysis from the first oil change instead of at 92,000 miles to see the progression - the way Blackstone does their reports, you get the current in the left column and then the prior 5 oil changes after the gray column (#2). I run those in my boats and have a pretty long history - 10 yearly reports on my current twin diesel (250 hours between oil changes or 1x year) and 20 years worth of data on my single gas engine (every 50 hours, minimum 1x year) boats.

cls33

How does age of oil factor in? I have <3k miles on my current oil, but it's been a year and the OLM is nagging me. Should I get it changed because of the age? I'm out of warranty so that's not a concern.

Patman

I started doing UOA on my C7s oil changes right from the first oil change, and will continue doing it for every oil change for the life of the car so it'll be interesting to see the progression of the reports. Even though I have been getting UOAs done since 2002, this is the first new car that I have owned in that time period, so this aspect of it is new to me.

With my C6 I was out of warranty so I was on a 2 year oil change schedule in that car with Mobil 1 5w30, and my oil analysis reports showed it to be a safe practice.

VetteDrmr

I started as soon as I could. I didn't do the first oil change because I had no idea what kind of oil was in it (Dexos bulk was what they used, but couldn't tell me if it was the blend or full synthetic).

I asked this of Blackstone a couple of years ago in regards to an LS1 Miata I have that isn't getting driven much anymore (in fact, I'm getting ready to sell it). They said that full synthetics, specifically M1 (a group 3 oil base), doesn't really age enough to be measurable. In theory they start breaking down as soon as they're exposed to air, but the rate of degradation is so low as to be irrelevant.

What I tell folks that run their cars short mileage is to make sure they get the oil temp (not coolant temps) up to at least 170 degrees for at least 15 minutes. That gets the oil hot enough to dry out the moisture that collects in the crankcase due to combustion blowby.

So, my personal limit is 2 years. Not because I think the oil is breaking down, but just because I want to get under the car and check things out. Reset the OLM and change due to mileage (pick your limit).

Oh, and take it as a personal challenge to ALWAYS have the OLM tell you to change the oil based on mileage and never on time!

Have a good one,
Mike

VetteDrmr

A true life quote...

But, my real question is, for a Group 3 oil (which is what most people will be using), do you know if the base viscosity is the cold or hot number?

I bet you could find people that would ask the question "what's the difference between castor oil, motor oil, and vegetable oil?"

The answer: One is a medicine that you think will kill you, one is an engine lubricant that WILL kill you, and the other you eat.

Have a good one,
Mike

AWOL

Mike

The wear trends are most likely staying the same.
What may be happening is because there is less time on the oil, there would be less time to accumulate the wear elements. I believe if you did a wear to time ratio, the wear rate would be the same

Patman

That is a good question that I'm not 100% sure on, as it's probably something that differs slightly depending on how each oil company prefers to formulate their oils. In addition to the different types of base stocks that a formulator has to work with, they can also choose from a different starting viscosity, so that could play a factor on whether they need to add more pour point depressants into the oil or whether they need to add more viscosity index improvers. That is why an oil with a better base stock will often be the better oil to choose, as it'll use less of those additives to get the desired viscosity, giving yourself an oil that holds it's viscosity better.

Bavaria

Now that the warranty's off, I'll change the oil/filter every two years or 10k miles, whichever comes last (just like we do on our high miles '07 and '10 Lexus').

orca1946

I put Mobil 1 in my 1978 trams am and the oil pressure seems to be higher the with non -syn. Every 2 year oil change scheduled