Oil Mixing and Viscosity

[Nomad Willy]

At times I have mixed 30w and 40w Delo. Usually less than 50-50 as in one quart 40w and 3quarts 30w. For summer use.

But now I am considering mixing 10-30 and 20-50. If the viscosity is linear up and down the scale as one changes vis I think one would come up w 15-40. But I don’t know if this is a linear function.

If 15-40 lube oil is readily available in 15-40 for gasoline road vehicles I’ll be good to go but I don’t think it is. However it would be handy for many of us to mix what viscosity we wanted relative to the variables at hand like low temps and flat land or high temps and mountainous roads. I don’t think 15-40 is available for gas engines. I wonder why but if one can mix per above anyone can mix up 15-50.

Mixing would mostly happen as I mentioned above .. like adding a quart of a different vis. Doing this the vis wouldn’t change enough to need numbers .. IMO. If you have a car in Wash state and the owners manual recommends 5-30 oil from Cali to Wn and in Wn the recommended vis is at max vis (per owners man) just adding a quart of lowest vis per manual should be safe and bring the oil vis up or down to a more desirable overall vis. No need for linear info either.

So is there any chemists aboard that know if one can mix and achieve these vis numbers in a linear way? And as usual I’m open to opinions.

 

[rslifkin]

Many of the diesel rated 15W-40 oils are also rated for gas engines, provided you don't need a specific spec for a Euro car or anything. That's what I run in the 454s in the boat.

 

[Nomad Willy]

rslifkin,
OK good …
But do I dare ask for high millage oil?
The diesel car I’m looking at is a Golf w 350,000miles.

I think I remember reading on the bottle/can that my Chevron Oil was good for cars too.

 

[rslifkin]

Personally I've never worried about high mileage oil as a concept. Just use something of good quality that meets any special needs for the engine in question and is of an appropriate weight for it. If in any doubt, do an oil analysis at the first change with a new oil.

 

[C lectric]

I used to use 15/40 in my two cars although they were 1988 and 1989 s plus my 1999 Ranger 3 L v6.
In fact when I pulled the head off mine 1998 at about 250,000KM there was no sign of the frequent ridge ring at the cylinder top.
Never a lick of trouble.

I'm not so sure I would mess with my boat engine like that though. If I screwed up the cost could be disastrous compared to the cars.

 

[Nomad Willy]

I put high milage oil in my 87 Nissan and it idled better and quit burning oil. Didn’t burn much but enough to notice.
The manufacturers seemed to think it was good. It was a new thing not long ago and I suspect they wanted to get past the “something new” resistance. Remember radial tires? Fuel injection?

I ran 30w oil in the Nissan for several years and the only thing I noticed different was a very slightly lower idle speed at startup. Probably 1/2mpg less gas milage but that’s fly stuff. I was concerned about the MV oil thining out. It probably does …. but not much now. Was a problem early on though I read.

With a car one is much more likely to go out of viscosity range. Not so w a boat. C lectric I don’t see how one could “screw up”. As I put it out one could only go in a beneficial direction w the vis if you thought it out. If you went higher vis in so Cal it would be a benefit or if you went higher vis in Wash it wouldn’t be a problem unless one made big changes in the heavier oil direction. But that would just reduce wear. The’re may be people on this forum that wouldn’t believe that tho.

 

[phillippeterson]

Remember radial tires? Fuel injection?

I remember my grandmother flipping out in 1960 at a new car with a tilt steering wheel. She just KNEW it fall off in her lap.

 

[FF]

What changes in oil as it gets "better" or at least newer is mostly the detergent level. All containers are marked with oil detergent style.

There are on line tutorials on the difference between CD ,compression engine , D rated oil and say SD , spark engine D rated oil.(damn little)

Thin oil might help cold starting and mileage , but for long life a single wt. oil still seems to be the champ.

 

[sunchaser]

Here is my oil change story that recently happened -

So I get a notice on my 4 year old gasoline Panamera that the 4 year servicing is due. No big deal on a car with 7,400 miles and only needing an oil change right? Wrong!

The maintenance mgr at the dealership says the manual calls for new plugs, serpentine belt, transmission, all filters and Mobil 1. All to the tune of over $2,000. Further, next year all new tires as at five years the speed rating is voided by government decree.

He said all the work could be done in three weeks as they are very busy. So I walked over to the sales manager's office and asked if they are offering really good deals on new cars. Hah! He says sales are up and inventories way down.

Well what the heck, what would you offer for my "new" car. He goes out and looks and then pulls it up on the computer.. We quickly arrived at a surprisingly good offer and I got a check. The car is whisked into the shop and all work commenced as I wait for the dealer's runner to give me a ride home. The next day the car is for sale at 90% of what I paid for it.

I also note Hertz is buying used cars as insufficient new ones can be found. These are amazing times Eric, your Rabbit may well be worth double what you bought it for, clean oil or not.

 

[catalinajack]

What changes in oil as it gets "better" or at least newer is mostly the detergent level. All containers are marked with oil detergent style.

There are on line tutorials on the difference between CD ,compression engine , D rated oil and say SD , spark engine D rated oil.(damn little)

Thin oil might help cold starting and mileage , but for long life a single wt. oil still seems to be the champ.

Straight weight, multi-weight, it doesn't matter a wit as to engine longevity as long as the oil is changed when recommended.

 

[rslifkin]

Straight weight, multi-weight, it doesn't matter a wit as to engine longevity as long as the oil is changed when recommended.

Pretty much, yeah. As long as the oil meets the basic needs of the engine in question (some engines have more specific needs than others and some engines are more abusive to oil than others) and you change it before the oil is sheared too thin, diluted with too much fuel, too dirty, or the additives are too worn out, then you're in good shape.

 

[KnotYet]

rslifkin,
OK good …
But do I dare ask for high millage oil?
The diesel car I’m looking at is a Golf w 350,000miles.

I think I remember reading on the bottle/can that my Chevron Oil was good for cars too.

In my VW diesel I've used Shell Rotella T-6 with very good results. It is 5-40 weight.
Oil change intervals are 10,000 miles per Volkwagen. T6 would be fine in any diesel.

I would never consider mixing oils to achieve some imagined benefit since the oil
manufacturers have already provided a myriad of choices to fit most any situation.

Interestingly, the engine builder of my 425 HP Ford V-8 gas engine recommended
Rotella T5 in that engine from day 1. So that's what I use. It is 15-40 weight.

 

[Nomad Willy]

At times I have mixed 30w and 40w Delo. Usually less than 50-50 as in one quart 40w and 3quarts 30w. For summer use.

But now I am considering mixing 10-30 and 20-50. If the viscosity is linear up and down the scale as one changes vis I think one would come up w 15-40. But I don’t know if this is a linear function.

If 15-40 lube oil is readily available in 15-40 for gasoline road vehicles I’ll be good to go but I don’t think it is. However it would be handy for many of us to mix what viscosity we wanted relative to the variables at hand like low temps and flat land or high temps and mountainous roads. I don’t think 15-40 is available for gas engines. I wonder why but if one can mix per above anyone can mix up 15-50.

Mixing would mostly happen as I mentioned above .. like adding a quart of a different vis. Doing this the vis wouldn’t change enough to need numbers .. IMO. If you have a car in Wash state and the owners manual recommends 5-30 oil from Cali to Wn and in Wn the recommended vis is at max vis (per owners man) just adding a quart of lowest vis per manual should be safe and bring the oil vis up or down to a more desirable overall vis. No need for linear info either.

So is there any chemists aboard that know if one can mix and achieve these vis numbers in a linear way? And as usual I’m open to opinions.

Straight weight, multi-weight, it doesn't matter a wit as to engine longevity as long as the oil is changed when recommended.

What matters is viscosity. Higher vis means longer life. And more residual oil is on the to be lubed parts at start up. A heavy synthetic clings to metal best but viscosity is king re wear.

 

[Nomad Willy]

KnotYet wrote;
“ Interestingly, the engine builder of my 425 HP Ford V-8 gas engine recommended
Rotella T5 in that engine from day 1. So that's what I use. It is 15-40 weight.
________________

I like the 15-40 oil in MV. Thanks for the comment. I’ll take it to the bank .. er garage.
So you use oli manufactured for diesel engines in your gas engine. What does your “builder” think about additive packages meant for diesel engines in gas engines? That’s something I wouldn’t do … normally but w his reco stacked on top of yours holds a lot of water .. or is it oil .. in my book.

 

[Nomad Willy]

Sunchaser wrote;
“I also note Hertz is buying used cars as insufficient new ones can be found. These are amazing times Eric, your Rabbit may well be worth double what you bought it for, clean oil or not.”

Golf actually .. and not this one that I sold.
The one I have now is silver w a 2.Ltr engine.

 

[mike66]

https://bobistheoilguy.com/motor-oil-101/
A lot of stuff on viscosity, temp, etc. Good read.

 

[rslifkin]

What matters is viscosity. Higher vis means longer life. And more residual oil is on the to be lubed parts at start up. A heavy synthetic clings to metal best but viscosity is king re wear.

Thicker oil protects better, but only up to a point. An oil too thick relative to what the engine was designed for may lead to issues if there are any small passages where you may get insufficient flow. Some engine designs are pretty fussy about oil weight, others will tolerate anything within a pretty wide range.

Of course, there's also concern for viscosity at cold start (and resulting wear from poor flow right at startup if oil is too thick). With the same engines I've got in the boat, I'd be running 5W-40 instead of 15W-40 if they were in an application that saw cold weather use.

 

[Ski in NC]

I too drive a diesel Jetta, yr 2001, 1.9ltr, 288k miles. Rotella T6 5-40 for last 200k miles. No issues.

Don't get too hung up with viscosity. Oil viscosity varies a LOT with temperature, whether a single grade or multi-vis. Between the two types of oil, the multi-vis changes less, but between cold and hot engine the vis difference is HUGE.

Don't worry about it. What ever oil you use the car will be a POS before the engine suffers a lube related failure.

I stick with T6 so the "hot" turbo does not coke the oil on hot shutdown. Original turbo still doing fine, so it is working. My Cummins 450 with water cooled turbo gets dino oil (T4).

 

[fgarriso]

Just ask VW

 

[Nomad Willy]

Ski wrote;
“Don't get too hung up with viscosity. Oil viscosity varies a LOT with temperature, whether a single grade or multi-vis. Between the two types of oil, the multi-vis changes less, but between cold and hot engine the vis difference is HUGE.”

Thank you much Ski. Took a long time to come out but this is very important. Oil coolers are golden I’m think’in. And running 30w in my little car with very little difference in idle speed (cold to hot) shows that even w “huge” difference in vis there’s almost no difference in how it runs.

Another thing that’s just a notion w me .. I’m going to mention.
If one started at the recommended vis and went (in vis) both ways the same amount I’ll bet running extra thick oil is FAR better than running extra thin. This is assuming plenty of warm up time running. Re this I’m inclined to think that small changes in vis are also more likely to be good or bad. And if you run just outside the range of recommended vis it’s better to be on the higher vis end. And if you have cold start running issues in mind just warm up longer.

Ski,
How is power (low to mid range) tween the Jetta 1.9 and the 2 Ltr. gas engine. Mine may have issues as it has two flat spots. One low-mid range and the other next to the top end. When I put my foot in it it has more power when I pull my foot back a bit. A NA engine shouldn’t do that I’m think’in. Most people wouldn’t notice … not as noticeable as the flat spot w the 1.8 turbo … usually called “turbo lag”.

 

[Nomad Willy]

https://bobistheoilguy.com/motor-oil-101/
A lot of stuff on viscosity, temp, etc. Good read.

Mike66 wrote;
“A lot of stuff on viscosity, temp, etc. Good read.”

A lot of stuff indeed.
Bob is the oil guy breaks down what is a condensed history of the evolution of modern internal combustion engines lube oil development. It’s far to complicated for most all (and maybe all) TF members. He subscribes to 4-5 things I don’t buy into like the notion that most engine wear takes place during start up.

But I learned quite a bit by reading the intro chapters and plan on reading more. His concepts about the starting and warm up stage of lubrication followed by the warm/hot operating range I liked. And that the problem is in the start/cold stage and warm operating range of lubrication is relatively easy.

A part of the picture That I’m vague about and think is important is the great emphasis placed on low friction, efficiency and economy. I wonder if sacrifices in engine life and sales in our world of dwindling recourses and the popularity of “eco” things has led the auto and oil manufactures down a road of “buy this it’s popular and modern”. I remember modernness was popular in the fifties and in most of recent history. But it’s especially strong now.

The info presented in the “oil guy’s” presentation is worth reading again and I plan on it. If I succeed I’ll post another response. I should really take time to take notes.

 

[psneeld]

My question for the future will be...all the hybrids and some gasser cars have engines that shut down and start up at every red light, some stops signs...etc...etc...what will that trend show for starting wear?


Can't wait to see what the consensus is about that effect on starters and engines over the long haul.


I would think hybrids have been around long enough that maufacturer's are still using the auto stop/start on 2021 gasser vehicles.

 

[rslifkin]

My question for the future will be...all the hybrids and some gasser cars have engines that shut down and start up at every red light, some stops signs...etc...etc...what will that trend show for starting wear?


Can't wait to see what the consensus is about that effect on starters and engines over the long haul.


I would think hybrids have been around long enough that maufacturer's are still using the auto stop/start on 2021 gasser vehicles.

Most of those systems use a significantly different, beefier starter. Both to handle the extra cycles better, but also as part of their method for ensuring fast enough restarts. I'm not sure what, if anything, the manufacturers have done to mitigate oil related wear concerns (although it's less on a warm restart than a cold start).

 

[jleonard]

My question for the future will be...all the hybrids and some gasser cars have engines that shut down and start up at every red light, some stops signs...etc...etc...what will that trend show for starting wear?


Can't wait to see what the consensus is about that effect on starters and engines over the long haul.

Yes it will be interesting.
In some applications bearing wear is a function of number of starts.
When I was working as an engineer we supplied to the company that handles all the spare parts for the postal trucks. On a tour there we were told that average life of a starter in a postal truck is 6 months.
Makes one think.

 

[Nomad Willy]

Jay,
Are postal trucks gas or diesel?
The little “mail delivery trucks” are probably mostly or all gasoline.
But the brown UPS trucks are diesel. Don’t know if they shut off at each stop tho.

The max wear on startup theory is predicated on (presumably) the fact that oil is liquid in nature and then drains down the cylinder walls.
When I was flying ultralights I took off the exhaust manifold and looked into the exhaust port. I could see the oil on the piston skirt .. profoundly so when running very high vis motorcycle racing oil. This oil (Bell Ray) had such a high viscosity it was not recommended for oil injection systems on 2 stroke engines. The only oil that was not. For that reason I used it as an oil viscosity improver in a very noisy boat transmission. It got the job done.
But with Bell Ray or other oils I could see what appeared to be brush strokes on the piston skirt and my finger confirmed it was oil. So IMO the high wear at startup notion dosn’t hold water.

Any comments on mike66’s Bob the oil guy?
He mentions (supports) high startup wear.

 

[jleonard]

Jay,
Are postal trucks gas or diesel?
The little “mail delivery trucks” are probably mostly or all gasoline.
But the brown UPS trucks are diesel. Don’t know if they shut off at each stop tho.

I'm speaking of the gas trucks, the ones on the 1980s S-10 frame with the aluminum body that you see everywhere. There are about 140K of them in service.
They are not "stop/start" but they are moved and shut off and started many times each day.
Hopefully a better, longer lasting starter is in the newer vehicles

 

[diver dave]

Nomad. Not just the pistons.. Shell bearings need pressurized oil to minimize wear. Cold oil (more precisely thick oil) flow is poor inside the journals. They want oil that flows well, ASAP at startup. That would be thin oil, but that “thinness” is bracketed on the thin side but the ability to maintain pressure, esp hot motors at low rpm.

Oh, my last PRC trip about 5 years ago, had my metro bus diesel shut down at EVERY stop. Also, no towels in the mens room. I think those two process' are related. :lol:

 

[Nomad Willy]

diver,
That’s the theory.
But like religion a theory I don’t accept.
“ Cold oil (more precisely thick oil) flow is poor inside the journals. They want oil that flows well, ASAP ” the necessary oil is already there.
But my opinion is …. Opinion.

 

[diver dave]

It is a fairly consistent message to warm up the engine before hard use. There is a tremendous change in oil viscosity, hot to cold, even with these 0W-x synthetic oils.

 

[rslifkin]

diver,
That’s the theory.
But like religion a theory I don’t accept.
“ Cold oil (more precisely thick oil) flow is poor inside the journals. They want oil that flows well, ASAP ” the necessary oil is already there.
But my opinion is …. Opinion.

A thick oil will take longer to drain off, but depending on the area of the engine to be lubed and how long it's been sitting, it can still get down to an insufficient film for lubrication. And with thick oil, it takes longer to get good flow to some areas (particularly valvetrain components) at startup, so they have to rely on that leftover oil film for longer.

Plus, there comes a point where thicker oil doesn't meaningfully impact wear and just costs power and fuel consumption. How thick you have to go before reaching this point depends on how hot the oil runs in a given engine (and therefore actual operating viscosity) as well as the bearing design and loading.

An engine with highly loaded small bearings will need thicker oil than a design with large, lightly loaded bearings. How much oil pressure the engine runs (based on pump relief valve setting and oil pump volume) also determines how thick an oil it takes to maintain a sufficient oil film in the bearings. That's why running, say, 0W-20 isn't a big deal in some modern engines, but you'd be crazy to expect good results in an older engine that was designed for a 30 or 40.