Viscosity? We don't need no stinkin' viscosity...

Recently we had a civil, if short of fact, discussion on the value of viscosity. The question was posited as to the true value of 0w-20 and 5w-20 in our C's. I've always been one to ask Why?, and was taught many years ago to question those that say "We always did it that way." or "Because the book says so." When working on an aircraft, things are done by the book. The book has the experience of thousands of engineers and maintenance gods. Routing messages over a military comm line, you take your addresses out of a book that gets updated every night at 0001hrs. You never route from memory - you always get the address out of the book. But what about maintenance from the Toyota book? Books from different countries and regions differ in their recommendations for the same physical vehicle. Other things will obviously work and not damage the vehicle. But you don't know anything about oil, oil types, oil weights, or oil viscosity? What to do?

What to do, indeed. Where in that maintenance manual must you do precisely what it says and where is there a "suggestion" or "recommendation?" Sometimes it's spelled out or is obvious. A sparkplug size would be pretty much a specific thing. Fuel octane is not written in stone, and you CAN use any of several different octanes. Tire size is variable, as is inflation pressure. But, obviously, there is a range of sizes that work and some that don't. You don't HAVE to wash, wax, and clean inside and outside of your vehicle, but if you want it to last longer and look better it would be a good idea.

How much you follow the book would be a function of how much you know, how much experience you've had stretching the recommendations, and sometimes just plain old observation.

Which brings me to where I was headed...Oil, and oil viscosity as it relates to our C's. I have attached a chart of various oils and their viscosities. Our prior conversation touched on the maintenance recommendation (more like the insistance, with stink-eye) of using 0w-20 in the C. I raised the idea that this particular item may be flexible. That idea was not universally accepted.

Taking a quick look at the charts in the attached file, you'll see two tabs. One tab has the oil brands and weights listed in order of cooler viscosities, the other has them listed in order of operating temp viscosities. The 0w-20's are highlighted in green, the 5w-20's in yellow, and a single 5w-30 added in red for a reference.

Checking the cool oil order of viscosity, you can see which might be most mpg-efficient if you drive in the city or your engine most often sees cooler temps. Looking at the hot driving tab you can see which oils might be most mpg-efficient if you drive mostly on the highway or your engine is always warmed up and ready to go.

These are all numbers taken from the manufacturer websites this week, so they are recent numbers.

But what I find most intriguing and thought provoking, as it relates to the maintenance manual oil viscosity heavy-handedness, is that the viscosities of the 0w and 5w 20w oils OVERLAP. This is most evident in the hot driving tab. Imagine the heads exploding seeing an actual 5w-20 has the lowest hot viscosity! Oh, and look at the alternating viscosities after that one.

Read this part carefully - I am not telling you how to maintain your car. I am not telling you what to do. If you want to go by the book, I DON"T CARE. Go for it. But if all you are going to do is blindly repeat the maintenance manual and give no further reasoning...go back into your hole. I am not interested in Absolute Maximum Effectiveness or MPG. That would be an opinion or a statement impossible to prove due to the myriad control points. Make a statement, defend your statement.

Now...discussion?

 

A quick check of some of the oils, but of the seven I've looked at not one of them is A5/B5 rated. The ones that were rated were A1/B1, and the others not ACEA rated at all. Yet, no complaints have been heard from 10k mile intervals for the M1 extended performance, or the M1 0w and 5w-20 M1 and M1 high mileage. I'll look into it more when I return from lunch.

"A5 / B5 - For use in high performance car and light commercial petrol and diesel engines designed for low viscosity oils where extended oil change intervals are specified by the vehicle manufacturer."

 

Who ever knows how long the ride when they get a new car, wife, or anything else. The '89 CRX I had prior to the C had 288k miles on when it left my driveway. I had only put a few on it, but it was still a viable car that would get out of it's own way. Would the guy in MN have thought it would have been a 300k mile car when he drove it off the lot?

I've learned to take care of my stuff over the decades. Cars, tools, wives, children, friendships...they all require care and maintenance. And proper maintenance requires a desire to know and a certain amount of bravery.

 

Dr Haas' oil info is truely enlightening, but geared towards those who operate their cars towards the edge of the envelope (sanity?) At that point there is little slack to be had, and being able to crunch the numbers is mandatory if you want to keep your $750k grocery getter. I wouldn't think that our C's engine is very stressed or abused, even when floored over and over and over and over. The redline shows as mid-4grands, and that ain't nothing'. The only REAL stress it would see is starting it up in sub-zero weather and mashing the gas to the interstate and repeating daily. Viscosity numbers at that place would be very much a thing to know and watch.

But anywhere else, is it really all that big of a deal? Really? We've seen or heard of cars that are severely abused and neglected going over 200k miles, or maybe Uncle Joe's car had cheap oil replaced at extended intervals by more cheap oil, yet lasted long and left the driveway for the next owner under it's own power.

How much of an issue is it to put in a heavier oil over the winter? Wear at startup? How much is too much, can you quantify it (other than maybe UOAs) and where do your habits bring down the pointer?

 

These are examples of what I was attempting to avoid. Agreed, it makes for a short thread, but there it is.

"The Correct Grade" is subjective. Correct grade, per what? Maintenance book? What about summer, winter, severe duty, mountains, long periods of activity/inactivity, etc? Does it even matter? That's what started this whole mess. Blind obedience at face value with no ide of the 5 W's plus a How. Quantification, Man, that's what we're waiting for.

As for WHEN to change oil, same thing. Intervals are always selected for a very good reason: payday, blind obedience, severe duty, the perception of "better," oil was on sale, "Winter's Coming." etc. Is there an ideal mileage/date/ moon cycle? By whose reckoning?

Your cars could all have met the same fate if you used a different oil, oil weight, manufacturer, or change interval. The question would be, how much change to what variables would yield approxmately the same result.

My contention is that....nobody will ever know. Precise life cycle per oil weight, brand, bottle color, or change interval can never be known. The point being, blind adherance to a maintenance schedule would be sufficient, but so is changing early, changing later, and using different or the same oil weight. Short of totally abusive behavior, What Difference Does It Make?

And if anyone can quantify an argument against that, I'm all ears.

With all this going towards the idea that it's rude to fight over oil weights and change intervals. Practically anything will do, and it doesn't take a Toyota engineer to tell us that.

 

Your post is guesswork and supposition. There are no numbers.

We have already seen the C capable (and authorized by the company) of using from 0w-20 to 50w oils, depending on regional temps and oil availability.

But, if the C has VVT, and if the world-wide C family can use each of the oil weights I have previously show it
capable of using (depending on regional temps) how tempermental can VVT in the C possibly be? Perhaps there are some vehicles with VVT that really need to watch their oil temps/viscosities, but is the C one of them?

Does that old mechanic always use such dire sounding generalizations? Does he really know anything, then? How do you know that he knows what he's talking about, if you don't know what he's talking about?

And about that Why Not Use What the Book Says? I'm not telling you not to. I don't mind. If you don't know why you might do something different, and when to do it, then those people SHOULD go by the book without thinking about it.

 

That isn't what was asked...

But while I'm here, I have Pennzoil Pure Plus 5w-20 standing by for the next fill. I will get UOAs for this fill and that. I'll likely go to a 30w after that just to see what the deal is.

I think watching the heads explode will be entertaining.