When does it make sense to use different oil?

[R Shaffner]

This is NOT another oil thread. At least that's not my intent. Lots of information has been posted about what BMW specifies. What I'm talking about here is when and why one might want to intentionally deviate from BMW's recommendations.

The question is somewhat rhetorical, since I have some thoughts of my own and I'm curious about others' reactions, suggestions, and experience.

For starters:

Changing Climate/Seasons --

This is old school. Thinner oil for colder climates; thicker for hotter. This is covered by factory specs. Modern multi-viscosity oils have basically eliminated the need for this unless one's climate is extreme.

Using Thicker Oil in a Worn Engine --

This is old school as well. Using thicker oil can help slow down leaks, help compression and reduce oil burning from worn rings. Some examples:

When I was young the family's Chevy wagon overheated badly and developed a steady knock. I poured in a can of STP oil treatment, which is thick as syrup, and it stopped the knocking at idle. My mom thought I'd fixed it, but my dad knew better. It just made it quieter and MIGHT have made it last a little longer.

My brother's '92 525 has 290,000 miles and is a daily driver. The engine has never needed a major repair. Of course, it leaks and burns some. He'd been using 10W-30 for decades. I suggested that he try 15W-40 or 20W-50. He did and said the oil consumption was cut in half.

Several decades ago I bought a '72 2002. When I got home after a 3 hour drive I noticed the car was more than a quart low on oil but the light never came on. Upon further investigation I found that the jerk PO had removed the bulb for the warning light. When I replaced the bulb I found that the oil light stayed on at idle (probably worn bearings). I fixed the leak and put in a blend of 30w and 10w-40. That made the light stay off. I told all that to the guy I sold it to, but I don't think he understood what I was talking about. So long as the light was off he was happy.

Using Thinner Oil to Improve/Restore Circulation to Problem Areas --

The engine on my '97 540-6 had always purred until the chain guides went at 160,000 miles. After replacing those it had a bad case of lifter knock that wouldn't go away after revving the engine for a few minutes (per BMW's treatment) or several weeks of driving.

I read all I could find at the time and figured the problem had to be related to oil flow to that lifter. (I doubted that it suddenly failed while I was replacing the guides.) The recommended oil for that car was 15W-40 Rotella. (Yes, conventional diesel oil.) In this case, I thought thinner oil might help.

My logic was this: If the oil pump and pressure relief valve are working properly, and the bearings are OK, then the system will develop the spec pressure with any kind of oil. So with the same pressure, which oil will flow more easily into a sticky lifter (or anywhere else)? Thinner oil, of course. I changed the oil to 10W-30 synthetic and the knocking went away in a week. (Of course, it might have gone away anyway. Not sure, but I liked my logic.) Then I changed back to the standard 15W-40.

Others say that putting a quart of ATF in the oil can also help with noisy lifters, because of the detergents in the ATF. Also, ATF looks thinner and I doubt it has the same multi-viscosity properties of the oils we use. In other words, does adding ATF also make the oil thinner, especially at operating temp? I bet so.

Using Oils with Different Detergents --

I was discussing all this with a doctor friend of mine one evening over whisky. He laughed when I gave him the thinner oil example above, and said it reminded him of using blood thinners to get around blockages and dissolve clots.

Then he wondered about the detergents in the oils and drew a parallel to using a variety of meds. Chemotherapy is rarely done with just one drug. They use several and even call it a "cocktail." And often a variety of antibiotics can be used when one doesn't seem to be working. As we talked we wondered whether it would make sense to intentionally change types/brands of oils every now and then, or perhaps regularly, to give the engine a different diet of detergents.

When I got an '02 540-6 a few years ago, it had 150,000 miles and a clogged OSV. It looked like it hadn't been treated real well, at least lately. Spec for that oil was LL synthetic, and I knew I'd use that over the long term. But to clean everything out I decided to use a variety of oils and to change it often. I used 0W-30 synthetic for a few thousand miles. Then I tried the 15W-40 Rotella with those diesel detergents for a while. Then I went to Castrol Edge 5W-40. And now I wonder whether I should just rotate through the different brands of BMW-recommended LL oils with each change. Or buy what's on sale. Why not? It can't hurt. If the detergents are basically the same then it won't matter. If they are different, then it might help.

In other words, most of us pick a weight/brand and stick with it for many years, even the remaining life of the car. Like how we used to drink beer. But is that really best for the car? Would some variety be better?

[geargrinder]

Shaffenreffer:

Re: the 'thin oil' angle and the detergents angle... I'll absolutely corroborate that. In my 'varnish flush' threads/posts I've mentioned using 10W20 PZ conventional as a short-interval, light-load, 'cleaning' oil, especially to try to flush out anything in the 'embedded' check valves. I believe it really worked actually. That was a tip I tried from "BITOG" where you can delve deep into oil lunacy but also find nuggets from proper chemists and engineers. Overall you might go browsing around over there, but there's all kinds of stuff so you have to pick and choose what seems sensible. But you'll see a lot of info over there supporting the idea that PZ convench has really high detergent packages and is good for such situations, good for things like buying that used car that had been "long-change neglected" by the PO. I'm not sure I buy the idea at all that you need to cycle through 5 different packages, I'd be more inclined to identify one high-det-pkg product and use that when the cleaning is needed, then change out for a high quality standard oil. Extra additives of course, if they aren't needed, are likely actually impairing the fundamental oil performance...

Re: the thick oil angle, yeah I think for a truly (like you say, oldskool...) 'big clearances' worn out motor situation that sure still works but I've also found / seen counterintuitive things.

Guys who try to glob up start-up-rattle M62's with fat oil in the hopes that it keeps the tensioners and lifters stay pumped up, tend to find it doesnt really do what they hope. My flush-fix worked 100% and it was essentially the opposite theory. I've posted many times about the wife's oil-eating VAG engine (2.0T FSI, known oil-eater with a PCV system design flaw...) doesnt' really respond to thick-oil at all, if anything indeed it also makes it worse. What has been miraculous was a LubriMoly Leichtlauf, not in a heavier than spec grade, its something about the magic additive package works. The hypothesis there is probably that the defect for oil burning is some kind of a breather-valve clogging/sticking issue, and thicker oils actually make that worse, while the magic foo foo dust in the LM product is just the right thing to keep everything working the way its supposed to while providing good engine lube.

I think there's a couple other things about 'old-timer thick-oil common knowledge' that doesn't apply 100% anymore. I definitely no longer believe in the "put THICK stuff in or you ain't ballar racecar" approach. For one BITD thick grades were generally always the better / topline products, technology wise, and that was ONE reason they got used/spec'd/recommended. No longer, now all the big mfrs have high tech 0W or 5W or 10W 40's that have all the latest bells and whistles. In addition, modern motors, including performance motors, have much tighter tolerances, meaning a super thick oil not only isn't required but is perhaps sub-optimal. Engine wear aside for the moment - unless you're truly truly truly hard tracking that motor and getting that block up to max temp for extended periods (situations where the engine may operate past the far side of the visco spec as it starts to taper down...) - the idea that you need a 50 or 60 cuz you a ballar hard drivin' bro, I think is really outdated and erroneous. For the vast majority of guys even with fancy cars, unless the mfr says otherwise, one of these high tech 0W40/5W40 etc. syns is gonna be the bestest grade for sure. This is different from BITD when it was common for performance motors to be built even from the factory a little 'looser' (Porsche engines for instance?) and therefore justifying a thicker oil to maintain film, and, the temperature characteristics of the grade were not as good so you wanted to 'overshoot' so it had good performance at the highest stress points... The cars are far tighter and the oils are far better now is what it boils down to. Again if your motor is all worn and sloppy, that's a different story of course...

As I write this I think there must be 100 threads on BITOG explaining this stuff and talking about how any engine really has one optimal visco grade based on expected operating temp & clearances in order to maintain film-strength, and how all we are trying to do is adjust through either technology (visco-temp tech/additives) or grade changes, to compensate for changes in the op temps or clearances...

[BimmrMeUpSnotty]

Ooooh, another oil thread....

[R Shaffner]

Thx, GG. I always learn from your posts.

I agree that I probably don't need to rotate among different spec oils. I'm just coming to the conclusion that I don't need to pick one and stick with it, as I've usually done, either.

[BimmerBreaker]

My logic was this: If the oil pump and pressure relief valve are working properly, and the bearings are OK, then the system will develop the spec pressure with any kind of oil. So with the same pressure, which oil will flow more easily into a sticky lifter (or anywhere else)? Thinner oil, of course. I changed the oil to 10W-30 synthetic and the knocking went away in a week. (Of course, it might have gone away anyway. Not sure, but I liked my logic.) Then I changed back to the standard 15W-40.

The oil pressure valve will help set pressure, but oils of a different visocosity will have different flow rates to maintain that pressure vs other types of oil. It wont vary by a huge amount but its not accurate to say all oils flow/move the same way in the engine as that is part of why we spec the oils we do. Thicker will flow slower with a higher pressure and thinner will flow faster with a lower pressure.

Theres already a mix of detergents in oil as well. Not like Mobil1 uses one detergent an shell another, they all use mixes. As the oil is worn the detergents and other additives are consumed, so just changing the oil and replacing with whatever was in there is fine. Think of it not like each oil as their own individual chemo drug, but rather each oil as a pharmaceutical company's chemo drug cocktail. Shell uses this mix, Mobil might use a bit more of this or that...
Now if a car is abused an occasional "cleaner" oil run on a short interval could be fine. But just swapping to different oil changes at each change interval wont benefit much imo

So no, imo, use an oil your engine is happy with and stick to it

[edjack]

A periodic shot of Rislone couldn't hoit.

GG: BITD? Back in the old days?

BITDG?

[BimmerBreaker]

Bob Is The Oil Guy - it's a website/forum dedicated to all things brown and lubricious

[TerraPhantm]

I think there's a couple other things about 'old-timer thick-oil common knowledge' that doesn't apply 100% anymore. I definitely no longer believe in the "put THICK stuff in or you ain't ballar racecar" approach. For one BITD thick grades were generally always the better / topline products, technology wise, and that was ONE reason they got used/spec'd/recommended. No longer, now all the big mfrs have high tech 0W or 5W or 10W 40's that have all the latest bells and whistles. In addition, modern motors, including performance motors, have much tighter tolerances, meaning a super thick oil not only isn't required but is perhaps sub-optimal. Engine wear aside for the moment - unless you're truly truly truly hard tracking that motor and getting that block up to max temp for extended periods (situations where the engine may operate past the far side of the visco spec as it starts to taper down...) - the idea that you need a 50 or 60 cuz you a ballar hard drivin' bro, I think is really outdated and erroneous. For the vast majority of guys even with fancy cars, unless the mfr says otherwise, one of these high tech 0W40/5W40 etc. syns is gonna be the bestest grade for sure. This is different from BITD when it was common for performance motors to be built even from the factory a little 'looser' (Porsche engines for instance?) and therefore justifying a thicker oil to maintain film, and, the temperature characteristics of the grade were not as good so you wanted to 'overshoot' so it had good performance at the highest stress points... The cars are far tighter and the oils are far better now is what it boils down to. Again if your motor is all worn and sloppy, that's a different story of course...

As I write this I think there must be 100 threads on BITOG explaining this stuff and talking about how any engine really has one optimal visco grade based on expected operating temp & clearances in order to maintain film-strength, and how all we are trying to do is adjust through either technology (visco-temp tech/additives) or grade changes, to compensate for changes in the op temps or clearances...

I will say one area that high viscosity oils have an advantage to low viscosity even today is the HTHS value. That would probably play a role in engines that see stupid high piston speeds, like say the S54. Though even there I'm skeptical of the 10w-60 requirements.

[Santaclaus4]

I've heard since I was a kid is the 70's (HS freshman in 1979) that most engine wear come at the first 30 seconds on cold start-up. I don't think that has changed one bit in the last 40 years. Unless your engine has a pre oiler installed, I'm thinking the most appropriate oil would be for cold engine starts is the most important, followed by an appropriate oil for your average driving conditions with a little extra margin.
Of course that doesn't tell anyone what's the "best oil" but it my be the best advice.
That being said... if your engine is worn, tired, and noisy... There isn't a lot you can do. Thicker oil will offer a little extra cushion and make it slightly quieter for a while. That's cause you didn't start eating right when you were in your 20's and now your taking pills to make up for it. Lol

[TerraPhantm]

I've heard since I was a kid is the 70's (HS freshman in 1979) that most engine wear come at the first 30 seconds on cold start-up. I don't think that has changed one bit in the last 40 years. Unless your engine has a pre oiler installed, I'm thinking the most appropriate oil would be for cold engine starts is the most important, followed by an appropriate oil for your average driving conditions with a little extra margin.
Of course that doesn't tell anyone what's the "best oil" but it my be the best advice.
That being said... if your engine is worn, tired, and noisy... There isn't a lot you can do. Thicker oil will offer a little extra cushion and make it slightly quieter for a while. That's cause you didn't start eating right when you were in your 20's and now your taking pills to make up for it. Lol

I agree that’s likely the case for most people in most usage scenarios. Exceptions would be cars that see significant track usage. That’s why I always try to run a 0w-30/40 oils over a 5w-30/40 on my non-M engines. Both are acceptable, but the former should be better for cold starts.

[geargrinder]

Really I think the 5W oils even are still pretty fine even for winter startups, its more the "20W" soup that guys put in because they're stuck in the oldskool that really probably isn't good if you live someplace with real winter... But we're all generally agreeing here for the most part. (DEFECTIVE oil thread - too much agreement!)

[Mike WW]

I've heard since I was a kid is the 70's (HS freshman in 1979) that most engine wear come at the first 30 seconds on cold start-up. I don't think that has changed one bit in the last 40 years.

I've certainly seen that too, but I'm doubtful, though admittedly I'm not a chemist or mechanical engineer. But I have taken apart engines that have sat for years, even overheated just prior to shutdown, and there's always an oil film in the bearings and between the pistons and cylinder walls. I suspect there's more wear under extreme conditions, climbing that 8,000 foot pass doing 75 or trying to. The occasional exercise running it thru the gears up to or near redline.

[JimLev]

I've taken apart engines that have sat for years, even overheated just prior to shutdown, and there's always an oil film in the bearings and between the pistons and cylinder walls.

Same here, SBC 283cu in, Nissan 300Z engine, BMW V8's, motorcycle engines, etc. They all had a nice film of oil on all the bearing surfaces and on the rings.

[BimmerBreaker]

That thin layer of film was pumped there when the engine was presumably last running.
So what happens when the engine is started with just that thin layer of oil and there is not yet adequete oil pressure built up for a few moments to re-supply the oil once that initial layer is displaced? I think that is when the startup wear occurs

[R Shaffner]

A periodic shot of Rislone couldn't hoit.

Thanks. I've wondered about that.

I didn't try it or any other solvent/cleanser for my noisy lifter because I thought it would take some time, at higher oil pressure, to dissolve and flush out whatever was clogging it. I've been reluctant to drive it for any length of time with anything other than motor oil in the engine. That's why I thought I'd try thinner oils, high detergent oils, etc.

If there is a next time, I'll prob try something like that at idle for a while, before draining the old oil out. And then try GG's approach for a while with light throttle. (Assuming I can drive that car for any length of time with light throttle.)

[R Shaffner]

For a while Castrol was running ads that said their Magnatec synthetic oil was designed specifically to help with cold starts. Once I saw a counter-top demo in an auto parts store that showed how much better Magnatec clinged to metal, compared to other synthetic oil of the same weight.

In spite of all that, I don't think the product line has been that successful. I've tried it some in my brother's e34 with 290,000 miles, but no hard data about results. (I guess that's why we have all these debates. Little or no objective data.)

[R Shaffner]

As follow-up...

My '97 540 made it to 220,000 miles without getting a clogged OSV. Spec for it was Rotella 15W-40 (conventional diesel oil, with all those detergents). Oil was changed every 3-4,000 miles.

When that car was totaled, I got an '02 540 with a completely clogged OSV. Spec for that car was LL synthetic. And less frequent oil changes. I installed an external OSV which worked great. I also decided to use a variety of oils, including some of that Rotella, and various LL synthetics (why not?). I also change it often, every 3-4,000 miles.

I had to replace the chain guides last summer, at 185,000 miles. I replaced the OSV and found that the clog in the old one was gone. It was completely clear.

[ross1]

https://www.youtube.com/watch?v=v9Sbo9RQA4w
"Prolong"

[geargrinder]

As follow-up...

My '97 540 made it to 220,000 miles without getting a clogged OSV. Spec for it was Rotella 15W-40 (conventional diesel oil, with all those detergents). Oil was changed every 3-4,000 miles.

When that car was totaled, I got an '02 540 with a completely clogged OSV. Spec for that car was LL synthetic. And less frequent oil changes. I installed an external OSV which worked great. I also decided to use a variety of oils, including some of that Rotella, and various LL synthetics (why not?). I also change it often, every 3-4,000 miles.

I had to replace the chain guides last summer, at 185,000 miles. I replaced the OSV and found that the clog in the old one was gone. It was completely clear.