Future is THIN

[jason07-1zzfe]

I didn't say fast acceleration. I said wide throttle opening/high load.
And that that's why I said it's hard to do with automatics. With a manual you don't keep it in lower gears. With an auto, you can coax it to upshift sometimes by lifting the throttle, then giving it more throttle after upshift, then do it again.
High load low rpm is best.

 

[bulwnkl]

quote:

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Originally posted by Jason Troxell:
What you say disagrees with BMW and SAAB

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It doesn't have to. Let me use an example to illustrate.

Let us suppose it takes 40hp to move a SAAB 9-3 down the highway at 75mph (don't know whether that's reasonable or not; doesn't matter for the example). What I'm saying is this: Causing the engine to generate only 40hp, never more, as you accelerate away from a stop sign on your way down the highway to the next town saves an enormous amount of fuel compared with using, let's say 120hp to accelerate the car to 75mph and then backing off to only 40hp to maintain cruise speed.

How you maintain 40hp output is flexible. What SAAB says (don't know what BMW says) is that it is more fuel efficient to open the throttle wide and use a higher gear (lower rpm), compared with lower gears (higher rpm) and less throttle opening.

You can achieve what I mention above the way SAAB is saying to drive. If you're running your 9-3 at only 1200 rpm, the engine may only make a maximum of 40hp or so at WOT. So, at that point, you are taking greatest advantage of the cycle efficieny of an Otto-cycle engine by running the throttle wide open. You are also maintaining only the 40hp output necessary to achieve and hold your desired 75mph cruise speed.

This seems too long to have helped me explain, but hopefully you can see what I mean.

 

[buster]

quote:

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There is just alot more too it than to say 20W sucks.

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Thats how I look at it. If you believe that oil analysis on BITOG is a credible indicator of engine wear, then you must think 20wts are great in vehicles that call for them. We've seen nothing but great reports from 20wt oils across the board. But as you said, viscosity is simply one variable.

 

[Willscary]

I drove a 1998 Chevy Prism 5 speed until very recently. This car is a twin of the Toyota Corolla. During the summer months my work commute of 60+ miles of almost all highway driving each way produced a fuel economy of about 40 mpg. The spring and fall might be 41 mpg due to less A/C use. In the Wisconsin winters, the mileage would drop to between 37 and 38 mpg.

I bought an '04 Malibu LS with the 3.5L V6 and the 4 speed automatic. This Malibu has about the same room in it as our 1999 Olds 88 does. However, it gets much better mileage than the Olds. On long highway trips I can get 33 mpg with the Olds. If I use it for my daily commute, I can get 29 mpg. The Malibu is averaging OVER 37 mpg!!! This is a midsize car with a 200 HP V6.

Of course, I drive like an old lady back and forth to work. I accelerate slowly, coast into slower speed zones, and drive the speed limit.

After reading everybody's comments, I started thinking about the great mileage I get with a car that is MUCH bigger than the Prism it replaced.

First of all, it has a relatively strong motor with very good low end torque. The Toyota 1.8L motor in the Prism was higher revving to get into a decent power band. Thus, the Prism did 2500 RPMs at highway speeds while the Malibu cruises at about 1600 RPMs. The Prism had to be revved to get up to speed without lugging the small motor. The Malibu can be accelerated to 55 MPH without breaking 1900 RPMs. The Prism had a drag coefficient of (if I remember correctly) .34. The Cd of the Malubu is .31.

I love the Malibu. The problem is...I love my 3/4 ton Silverado with the 300 hp 6.0L V8 also. The truck is my weekend warrier for maybe 30 miles on the days off, while the Malibu will rack up nearly 40K miles per year. If I didn't need the truck for my home projects, I'd dump it and just drive the Malibu.

By the way...because of this forum, I bought 5 qts of Mobil 1 5w30 for the Malibu and installed it last Saturday. This is the first time I have tried synthetic. I hope you guys are all correct about the virtues of M1!

 

[Bryanccfshr]

quote:

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Originally posted by bruce381:
IMHO 20wt does not cushion the puunding metal components take as as such intill something breaks used oil analysis will not show impending falure only wear rates.
bruce

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This makes no sense from a physics perspective. They are both fluids regardles of viscosity. You cannot compress a fluid. There can be no cushion in an oil film..it is as solid as the metal parts themselves.The only way to lose this uncompresable film is for the flow of oil through the bearings to stop or not be adequate in volume to maintain the uncompressable wedge of fluid. So regardless of viscosity the "wedge" depends on flow for volume and pressure to keep the flow going through that grinder we call a bearing.

This is why foaming is so dangerous... foam introduces air into the mix. Air compresses and the if you have compression you have a failed wedge.

[ August 26, 2005, 06:57 PM: Message edited by: Bryanccfshr ]

 

[darkdan]

Viscosity is a measurement of flow.

Therefore, if something can flow quicker then it will have more ability to leave the area while the two surfaces are being compressed.

 

[Bryanccfshr]

The flow direction is constant and as long as the pressure is mantained the amount of fluid entering the bearing is going to be constant. The oil enters one end of a bearing and exits the other. The friction the oil gives to shearing determines the backpressure it gives from the non pressurized side(could be expressed as either friction or pumping loss). The oil pressure keeps the flow entering the bearing a constant. The only variables is the distance the oil must flow before it no longer gives backpressure and its resistance to shear.

A thinner oil will have to travel a larger bearing (a larger diameter) to provide the same backpressure to prevent being squeezed out or go through the bearing at a higher velocity A thicker or more shear stable oil can tolerate loads without being squeezed out of a bearing at lower velocity and through a samller diameter bearing surface.
There are a lot more forces than fluid flow going on here but viscosity only changes one aspect of a fluids behavior and that is its resistance to flow. This probably explains why suuch a wide range can work within an engine. As long as the fluid can resist being squeezed out of a bearing (which seems unlikely to me because the rotattion is constantly drawing fresh fluid into the surface that needs protecting)it is a perfect barrier between moving parts.

If this was not acceptable we would be seeing much worst numbers in used oil analysis with lower viscosity oils in engines designed for them. I don't think this has anything to do with clearances but more to due with surface areas and the diameter of the bearings in engines designed for these lighter oils.
Some engines may intrinsicaly have design features that allow them to tolerate these thinner oils even though the oil was not in the designers mind at the time. That can explain why some engines not originakly specced for 20 wt can still thrive on them. But I wouldn't think of using them in a diesel or a big block.

20wts will become more common and the design features of engines that use them will become more commonplace.

I have no personal gripes with thick or thin. I am selling my Toyota

so I can buy an old used jeep XJ and play with the 4.0 engine. The Toyota has just been too boring for a guy who likes to tinker.

So I will go from running a light 30wt near 20 wt..to running heavy 30wts to possibly just running a 15w40 HDEO.
Regardless of my pontifications on the abilities of thin to work I have a prejudice towards more viscosity, not less.

 

[bruce381]

"There can be no cushion in an oil film..it is as solid as the metal parts themselves."

In a journol bearing this is WRONG, in hydrodynamic lubrication the oil in a journal bearing will form a "wedge" and the oil will float the crank BUT if the clearence is to great, speed to slow or oil to THIN boundry conditions will form and wear will increase especially if surface asperities break through the thin oil.
Oil will only become solid in elasto hydrodyanmic conditions such as seen in gear teeth where the oil is trapped and subject to high pressure it will form a solid. Journol bearings will not hold the oil and EHD lubrication will not occur.


"The only way to lose this uncompresable film is for the flow of oil through the bearings to stop or not be adequate in volume to maintain the uncompressable wedge of fluid. So regardless of viscosity the "wedge" depends on flow for volume and pressure to keep the flow going through that grinder we call a bearing."

Again WRONG viscosity is important to forming a oil "wedge" as I stated above so is flow, pressure, and even surface condition of the bearing. To low a viscosity a wedge will not form.

But to clarify I'm not worried about crank or rod bearing wear but other areas where a higher vis oil WILL due to film thickness cushion parts due to the heavier oil resisting oil film rupture.

Like Cam lobes, valve tips, cam thrust plate, valve train rockers, drive gears etc.

Why not just cut to the chase and run a 0/10 thats where it is going. IMHO >30wt nuh said
bruce

 

[nickmckinney]

quote:

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Originally posted by bruce381:

But to clarify I'm not worried about crank or rod bearing wear but other areas where a higher vis oil WILL due to film thickness cushion parts due to the heavier oil resisting oil film rupture.

Like Cam lobes, valve tips, cam thrust plate, valve train rockers, drive gears etc.

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But thats not what significantly wears on cars since about the late 1980's. Usually its valve guides and valve seats, followed by the rings coking. For any in the above list to go bad, the engine is really in trouble.

From my prior days in a busy engine shop, 99% of our work was head repair from either overheating, broken timing belts bending valves, or burnt exhaust valves.

 

[427Z06]

quote:

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Originally posted by Willscary:
I bought an '04 Malibu LS with the 3.5L V6 and the 4 speed automatic. This Malibu has about the same room in it as our 1999 Olds 88 does. However, it gets much better mileage than the Olds. On long highway trips I can get 33 mpg with the Olds. If I use it for my daily commute, I can get 29 mpg. The Malibu is averaging OVER 37 mpg!!! This is a midsize car with a 200 HP V6.

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A lot of the same mileage improving tricks are employed in this engine as Chevy's LS-x V8 series. Short, coated pistons, low-tension oil rings, rollerized valvetrain, reduced line pressure in transmission under cruise conditions, aerodynamic improvements, etc, etc.

Great for highway MPGs, but as soon as you have to do a lot of stop and go driving, curb weight will have a bigger influence on fuel economy.

Example using EPA numbers so we can compare apples to apples:

code:

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2005 Malibu Auto-4 3.5L/V6 22 City/32 Highway

2005 Corolla Auto-4 1.8L/I4 30 City/38 Highway

2005 Camry Auto-5 3.3L/V6 21 City/29 Highway

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[427Z06]

quote:

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Originally posted by nickmckinney:
From my prior days in a busy engine shop, 99% of our work was head repair from either overheating, broken timing belts bending valves, or burnt exhaust valves.

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I have to agree. We obsess over the most reliable parts of a vehicle.

 

[buster]

Most 20wts thicken to a 30wt grade and don't shear at all. Most 0w-30/40's shear down. So with the 20wts you still might be getting the extra "cushioning" over a drain interval due to oxidative thickening. No VII are needed for 0w30 and 5w-20 oils. When I drain the Mobil 1 0w-20 out it will most likely be a 5w30 oil.

 

[bruce381]

"No VII are needed for 0w30 and 5w-20 oils."

Unless PAO based they all need 4-7% VII, GPIII also needs some too.


"When I drain the Mobil 1 0w-20 out it will most likely be a 5w30 oil."

Possible if exceeds drain interval but don't do that LOL.
bruce

 

[dave1251]

bruce thanks for your posting I was wondering about Mobil 1 0w-20 becoming a 5w30.

 

[slickfisher]

The sad think is mfg's spend their money trying to get their engines to survive on super thin oils and lobby the oil mfg to make sure there is enough additives to make it work instead of doing real design work and comming up with technology that will make a real difference. Direct fuel injection comes to mind. VW Group and Isuzu (of all mfgs) have it. I've always though many hands were in the oil scene including the EPA. I remember as a tech seeing the first 7500mi oil change intervals in the owners manuals and fellow tech saying what the....
Meanwhile our dealer always advertised 3k oil changes.

 

[slickfisher]

quote:

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Originally posted by nickmckinney:

quote:

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Originally posted by bruce381:

But to clarify I'm not worried about crank or rod bearing wear but other areas where a higher vis oil WILL due to film thickness cushion parts due to the heavier oil resisting oil film rupture.

Like Cam lobes, valve tips, cam thrust plate, valve train rockers, drive gears etc.

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But thats not what significantly wears on cars since about the late 1980's. Usually its valve guides and valve seats, followed by the rings coking. For any in the above list to go bad, the engine is really in trouble.

From my prior days in a busy engine shop, 99% of our work was head repair from either overheating, broken timing belts bending valves, or burnt exhaust valves.

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Exactly. Especially the coking of the rings.

 

[ex_MGB]

AP - NEW YORK - "With crude oil prices already near record levels, Hurricane Katrina targeted the heart of America’s oil and refinery operations Sunday, shutting down an estimated 1 million barrels of refining capacity and sharply curbing offshore production in the region.

It is an area crucial to the nation’s energy infrastructure — offshore oil and gas production, import terminals, pipeline networks and numerous refining operations throughout southern Louisiana and Mississippi.

The impact was immediate Sunday night when electronic trading resumed on the New York Mercantile Exchange, as crude oil futures spiked above $70 for the first time since oil began trading there in 1983."

 

[ToyotaNSaturn]

In an effort to squeeze every MPG out of my daily commuter 4 banger, Pennzoil 5w-20 SM is now in the old Satty. Hopefully this will prove to be a positive move as the future is thin, and now the future is now in the crankcase.

I'm not worried about wear. As was stated before that 30wts shear back to 20wts anyway.

 

[buster]

Shell had a great article and bascially it showed a higher oil film with 5w-20 wts then thicker viscosities. As long as the oil pump can deliver proper amount of oil to the bearings, wear might be lower with 20wts as Dr. Haas has suggested. If you noticed, Pb(bearing wear) is non-existant with the 20wts so far. I paid $3.19 for regular this morning in Princeton. I'm not about to switch to a thicker oil. LOL...time to inflate my tires to 38psi's.

BTW, Ford did a tremendous amount of testing with 5w-20's. One of the cars was a V6 also.

 

[427Z06]

quote:

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Originally posted by buster:
I paid $3.19 for regular this morning in Princeton.

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Yep...at these prices, it makes economic sense to reevaluate lubrication selections depending on vehicle and application. Some may want to move back closer to manufacturer's recommendations.