Engine Oil FAQ

[Secret Chimp]

Riddle me this: why is it that after around 2,500 miles my car only seems to go through maybe a quarter of a quart of oil (it goes down so slowly I don't bother adding any until it gets to that point) and by the time I decide to add that quarter of a quart back, it starts to go through a quarter or less-ish of a quart maybe every two weeks or so? Is the oil I'm using losing viscosity and getting burned off by the time it's reaching that age or something, or am I just nuts? This is with Rotella 5W-40.

[Eye of the Tiger]

You don't have a diesel engine. You should cut off your cat.

[GoCougs]

I'm going to go with the latter - it's a matter of perception.

I've never heard of this oil, but most any modern vehicle with a modern petro-based oil will have 7,500 - 10,000 mile oil change intervals; meaning, without significant contamination and abuse (overheating) would the oil be shot by 2,500 miles.

[S204STi]

I'm going to go with the latter - it's a matter of perception.

I've never heard of this oil, but most any modern vehicle with a modern petro-based oil will have 7,500 - 10,000 mile oil change intervals; meaning, without significant contamination and abuse (overheating) would the oil be shot by 2,500 miles.

RotellaT 5w-40 is a diesel oil, synthetic I believe, and it also happens to have a very decent additive pack according to those who seem to know something about oil.  I doubt highly that it's too thin.  If anything its hot viscosity is higher than specified by your manual (but probably still fine for the car). 

Chimp, I would monitor how much oil you add every 1000mi; if it's excessive (like, 1qt or more every 1000mi) you can try another brand of oil if you want, but most likely you have an oil consumption issue IMO.

[S204STi]

You don't have a diesel engine. You should cut off your cat.

It's ok to use diesel oil.  Most of them are API SM anyway, which is supposed to be fine for your cats.

[hounddog]

Trying the 15,000 mobile 1 in my Durango with the extended life filter.  I figure it has to work because thats what BMW is using, so I thought I would try it.  Again.  Last time was in the Ram 2500.

Do us a huge service and send a sample out for analysis if you can without too much trouble, please.

I have about 9,000 miles on this oil and filter now.  I had to add about 3/4 of a quart today, is that normal for syn?    

I know, this is going to be hardly techinical, but the oil has a "smoked" smell to it and feels ever so slightly gritty.  Thinking I will only go another 3,000, or less depending on how it seems when I check it.  And, I have been checking it every time I fill up.  It is a pain, but that was how I found the low-ness.  

Questions; At what point should the Durango inform me that the oil level is low?  I would have imagined that it would inform me after 1/2 quart low.  

Also, how will adding oil due to low levels affect the later analysis?

[S204STi]

I have about 9,000 miles on this oil and filter now.  I had to add about 3/4 of a quart today, is that normal for syn?   

I know, this is going to be hardly techinical, but the oil has a "smoked" smell to it and feels ever so slightly gritty.  Thinking I will only go another 3,000, or less depending on how it seems when I check it.  And, I have been checking it every time I fill up.  It is a pain, but that was how I found the low-ness. 

Questions; At what point should the Durango inform me that the oil level is low?  I would have imagined that it would inform me after 1/2 quart low. 

Also, how will adding oil due to low levels affect the later analysis?

Isn't the max interval on your truck somewhat lower?  I don't know if I impress this hard enough or not, but really the owner's manual should be your final authority on oil change intervals, IMO, not advertising from Mobil.  If I were you I'd stop where you're at and take a sample.  Blackstone Labs has a section in the form you fill out with the sample to tell them how much "make-up" oil you added to keep it at the normal level.  That will allow them to factor that into the results.

As for having to add some oil... Mobil seems to burn off slightly more on some engines than other oils.  I've had to add up to .5 over 3k miles in my car, but right now I'm running Valvoline SynPower and I haven't had any oil loss.  You might want to consider that brand in the future, I've read good things about them.  Take it with a grain of salt as always.

Just to clarify, I am not a lubricants engineer obviously, but again I'd stop with your current mileage and reevaluate future OCIs based on the recommened intervals in your owner's manual. :)

[hounddog]

Thanks.

"Isn't the max interval on your truck somewhat lower?"

Yes, 7,550 for standard use.  However, I am trying out the "Extended Life" Mobile 1 and the proper Mobil 1 filter.  SUPPOSEDLY, if damage occurs to the engine as a result of using this extended life oil and filter they will make it right.  Not sure how much of a guarantee that is, though. 

I will send for whatever package I need to use for the testing. 

[hounddog]

Do us a huge service and send a sample out for analysis if you can without too much trouble, please.

Looking at the site, which test should I request?

[The Pirate]

Looking at the site, which test should I request?

Who are you going to be using for the analysis?

I've heard good things about this outfit (and they are independent, so minimal bias), and will be sending my oil there very shortly.

http://www.blackstone-labs.com/standard_analysis.html

[hounddog]

Blackstone, but they have several tests listed.  I am just trying to find out which one I should use.

[The Pirate]

Blackstone, but they have several tests listed.  I am just trying to find out which one I should use.

I would think the standard test with a TBN would suffice.  That's going to tell you how long you should be going between oil changes, and make you aware of any significant issues.

[hounddog]

Ok, thanks.

[Minpin]

I've mentioned this before, but Hounddog, do this on your boat too. It's even more useful, imo, since a major repair on a boat engine would be much more costly than your truck.

[S204STi]

I would think the standard test with a TBN would suffice.  That's going to tell you how long you should be going between oil changes, and make you aware of any significant issues.

Agreed.  Paying the extra for a TBN tells you how much of the additive package is left.

[Eye of the Tiger]

Here is some more oil information.
"The Motor Oil Bible". Not a bad read for a rainy Friday afternoon.

http://www.zag.si/~jank/public/bmw/oil_bible.pdf

[Eye of the Tiger]

This bible is a mind blow.

[giant_mtb]

Here is some more oil information.
"The Motor Oil Bible". Not a bad read for a rainy Friday afternoon.

http://www.zag.si/~jank/public/bmw/oil_bible.pdf

Reading it makes me feel like this: 

[GoCougs]

Don't agree with him in the least regarding synthetics; I don't think he made the case for materially longer engine life, more performance or more MPG with synthetics.

[Eye of the Tiger]

Don't agree with him in the least regarding synthetics; I don't think he made the case for materially longer engine life, more performance or more MPG with synthetics.

He does throw in a bit of unsubstantiated opinion into the mix, but that's easy to read through.

[r0tor]

i perfer this as its actually useful... http://ferrarichat.com/forum/showthread.php?t=136052

[S204STi]

i perfer this as its actually useful... http://ferrarichat.com/forum/showthread.php?t=136052

Yeah that is a good one.  I have it linked up in the OP.

[GoCougs]

He does throw in a bit of unsubstantiated opinion into the mix, but that's easy to read through.

I should have stated that I do agree with him on the longer oil change interval for synthetics, which can be an advantage. The problem there is that for example my Accord manual specifically states the factory-specified interval must be followed for both dino and synthetic (which implies that if there's an engine problem in the warranty period one can run into problem if the oil change interval was not followed).

[S204STi]

I should have stated that I do agree with him on the longer oil change interval for synthetics, which can be an advantage. The problem there is that for example my Accord manual specifically states the factory-specified interval must be followed for both dino and synthetic (which implies that if there's an engine problem in the warranty period one can run into problem if the oil change interval was not followed).

The issue, I think, is that it doesn't matter what your base stock is, ultimately it's the additive package that "wears out" as far as I can tell.  (Not a lubricants engineer speaking, so take it with a grain of salt).  So unless you're running that Long Life oil or something you're not likely at any significant advantage in terms of length of OCI using a synthetic.

[Eye of the Tiger]

The issue, I think, is that it doesn't matter what your base stock is, ultimately it's the additive package that "wears out" as far as I can tell.  (Not a lubricants engineer speaking, so take it with a grain of salt).  So unless you're running that Long Life oil or something you're not likely at any significant advantage in terms of length of OCI using a synthetic.

Mr. Oil Bible explains that the base stocks for conventional multi-weight oils have to start out thinner, as they rely heavily on viscosity improving additives to thicken the oil at operating temp. As the additives degrade, the oil becomes thinner and provides less protection. Synthetics do not rely on the additives to maintain their rated viscosity over time, and they naturally maintain that viscosity over a wider temperature range.

[S204STi]

Mr. Oil Bible explains that the base stocks for conventional multi-weight oils have to start out thinner, as they rely heavily on viscosity improving additives to thicken the oil at operating temp. As the additives degrade, the oil becomes thinner and provides less protection. Synthetics do not rely on the additives to maintain their rated viscosity over time, and they naturally maintain that viscosity over a wider temperature range.

Ah yes, forgot about that.  Although, I don't think that's hard and fast, I'm pretty sure some synthetics have to use polymers as well for the multiviscosity effect.

[GoCougs]

i perfer this as its actually useful... http://ferrarichat.com/forum/showthread.php?t=136052

Upon a quick scan I see some flaws there, too; that engine wear occurs on start up, that 5W-30 is not thinner than 10W-30 at operating temperature, and that thinner oils are "better."

[GoCougs]

The issue, I think, is that it doesn't matter what your base stock is, ultimately it's the additive package that "wears out" as far as I can tell.  (Not a lubricants engineer speaking, so take it with a grain of salt).  So unless you're running that Long Life oil or something you're not likely at any significant advantage in terms of length of OCI using a synthetic.

My hunch would also be that Honda simply hasn't tested their engines extensively on synthetic for extended OCI, since the vast majority of people don't use it (and so they can't justify the extra R&D dollars).

As it is, with dino, their OCI for the V6 Accord is ~7,500 and the I4, ~10,000 miles ("~" meaning it can vary but the goal is to use the oil life monitor). That's still pretty darned good IMO.

[rohan]

Upon a quick scan I see some flaws there, too; that engine wear occurs on start up, that 5W-30 is not thinner than 10W-30 at operating temperature, and that thinner oils are "better."

Why are these flaws- engines have less oil in them at start up and thinner oils are better for modern engines with tighter tolerances OEM.

[GoCougs]

Why are these flaws- engines have less oil in them at start up and thinner oils are better for modern engines with tighter tolerances OEM.

I have to admit I was a bit biased as he starts off with credentials that sound impressive, but ultimately don't mean squat; it matters little that he is a highly paid medical doctor that owns exotic cars.

Start up: Take apart any engine that has been in use, and the bearings will have oil in them, even after sitting unused for years. As the engine starts this residual oil creates the high pressure layer for lubrication within fractions of second; within this fraction of a second of starting the oil pump is already supplying the engine with oil. If there was truly more wear on start up (which IMO implies metal-to-metal contact), engines wouldn't last more than a few thousand miles.

5W-30 vs. 10W-30: Per my viscosity charts in my machine design text, 5W-30 is a bit thinner throughout the operating temperature range than 10W-30.

Thinner oils: it seemed he advocated thinner oils across the board, independent of engine design. Thinner oils are only proper if the engine is designed for 'em as you imply. An engine designed for 20W-50 would get destroyed with 0W-20.