maxxTORQUE | THE Magazine of the GM Diesel Community

Last August, the Phoenix debuted in our local car club’s “Show and Shine” – the culmination of 20 years of waiting, working and waiting some more as we built and rebuilt what is arguably the ultimate working pickup truck.

My son Jens stays busy with an international transportation company, keeping their aging equipment between North Vancouver and Lillooet running: laying track, operating heavy machinery and generally making himself useful.

Ever since high school, Jens has participated in an annual silliness around here known as The Birken Ralley. The local off-road enthusiasts spend all their disposable income and sometimes more to build the toughest trucks. Then – here’s the silliness – they get together every Spring and drive out into the bush to get drunk and wreck their masterpieces. Early on in the madness, Jens recognized the superiority of the 1967 to 1972 Chevy/GMC body style. The high degree of GM part interchangeability, the simple, classic lines, the uncomplicated, before-pollution-control systems and the heavier-than-today sheet metal convinced him that the last of the line, the ‘72, represents the zenith in the development of the North American pickup truck. Over the years, he has built up quite a number of these vehicles and he has come to understand them down to the molecular level. In his work travels, he keeps his eye out and knows the location and condition of every one within a couple of hundred miles of home.

Owners of the GM 6.5L buy their vehicles expecting the benefits of a powerful diesel truck: legendary towing and hauling along with excellent fuel economy — they expect big things from the 6.5.
For most however, the 6.5 has fallen frustratingly short in the power department. When the 6.5s were built, there really was no horsepower race and 190 HP was, well, “not bad”. Compared to the Duramax, 190 HP doesn’t measure up and, as we all know, power really does matter. To make things worse, the 6.5 problems have not been limited to less-than-desirable power; they have also had reliability issues – as we experienced for ourselves in the course of this rebuild.

Perhaps, in a quest for more power and reliability, you have searched some of the big name diesel upgrade companies only to conclude that there are not any products out there that will mollify the frustrations you have experienced with your 6.5. There are, however, solutions that will make these trucks perform like they should – at a price that can’t be beat. maxxTORQUE, seeking to get the word out about the hidden value of these vehicles, hooked up with Heath Diesel Power (HDP – www.heathdiesel.com) and asked them to build up a common 6.5L truck. Bill Heath, the owner, was delighted to participate noting that “the 6.5 is much-maligned due to the problems experienced with them beginning with the introduction of the 1994 models that featured the Stanadyne fuel injection system."

Why have a section about lubrication in a magazine about GM Diesels? Simply stated, there is a direct connection between lubrication and the health and life of your vehicles. GM has done its part by manufacturing these marvelous machines; each owner is solely responsible for their maintenance. As a Certified Lubrication Specialist (CLS), certified by the Society of Tribologist and Lubrication Engineers (STLE), I cringe at the misleading advertising, misinformation and lack of lubrication education for both consumers and service professionals. In this continuing series, Lube Notes, I seek to provide factual information on lubrication to allow readers to rise above all the advertising hype and half-truths in order to make informed decisions when selecting lubricants – engine oil, transmission fluid, gear lube – for their vehicles. With this goal in mind, I intend to educate, not indoctrinate. In fact, the information in these columns will equip you to see through the attempts at indoctrination that surround us. I want to begin with some fundamentals of lubrication and, in subsequent editions of maxxTORQUE, progress through lubricant formulation and applications.

So come along for the ride and be sure to jot down questions as you read. You will always find my email address at the end of the article, and I will be glad to answer your questions. Also, I will select some of the questions to publish in the next issue of maxxTORQUE.

The fish are in the freezer, and with that, it is time for my annual reel cleaning and vehicle servicing regimen; an oil change is always part of it. I am reminded of what that oil went through on all those fishing trips. It all started with a realization that my thermo-viscous fan should not be such a common occurrence. I seemed to fly effortlessly up steep mountain grades with my big camper load, on a 103ºF Arizona day, in air conditioned comfort, and in complete complacent silence, dreaming of bass boils. Then I awoke, eyes wide and startled, to the sound of a 747 landing on top of me… THAT FAN!

I wanted to silence that fan, and all heat issues its aural signature represented. I remember the first time I heard it, going 70 MPH on slight, rising terrain with NO load. On a 114ºF sunny day, it doesn’t seem to shut off. Adding insult to injury I know I am losing two to three miles per gallon whenever it is in full spin. I have heard the statement, “that fan is normal, be glad you have it,” a hundred times. I am glad. Glad I don’t have to believe that any more. What if I said that you are an oil overheater, and you have never seen it? Crazy am I? Do you have an oil temperature gauge? If you knew what your oil temp was when you towed through my back yard, you would own one. The oil overheats on every summer camping trip. Presently, oil is cooled indirectly at the stock engine mounted oil-water cooler. Oil heat must be conveyed to the coolant, then to the radiator, then to the atmosphere, making it indirectly cooled.

The last issue of maxxTORQUE Lube Notes explained the regimes of lubrication including Hydrodynamic Lubrication, Boundary Lubrication and Elastohydrodynamic Lubrication.  As promised, I will now talk about the formulation of motor oils and why we put all those additives in our oil.  Before we get into the formulations of the motor oils, we better take a look at the functions of motor oil.  If we understand what oil is doing, then we can better understand why we choose certain base stocks and additives.

Motor oil must perform the following functions:

Lubricate engine parts in order to prevent wear

Reduce friction and improve fuel economy

Maintain clean engine components

Prevent rust and corrosion

Minimize engine deposits

Provide engine cooling

Aid in engine starting

Provide ring seal for better combustion pressure

Each of these functions is vital to optimum performance as well as to the durability of the internal combustion engine.  Motor oils are complex lubricating fluids carefully formulated to perform all of these functions.

Motor oil is composed of base stocks and additives.  The base stocks are either petroleum or synthetic and the additives are chemicals designed to satisfy the functions listed above, depending on engine type and duty.

Grandpa used to lecture me about the importance of draining the water separator on his farm’s diesel tractor. This man, who wouldn’t hesitate to fix things with haywire or binder twine was, however, a purist when it came to maintenance. Experience had taught him that draining the water separator could mean the difference between a well performing engine and one with problems – or one that didn’t run at all.

The investment required to properly maintain the fuel system meant avoiding the corrosion and scoring caused by water when it runs amok in the fine-tolerance components of a diesel engine. Duramax engines are significantly more sophisticated than Grandpa’s tractor. One might think that these more sophisticated engines can look after themselves a little better. In a sense that is true: today, we have more feedback than ever coming from our engines. But to think that these engines can handle not being maintained as well as their less sophisticated forerunners is far from the truth. In fact, just the opposite: today’s fuel injectors and other components require much higher tolerances. Consider that a typical conventional diesel fuel system prior to the DMax operated at fuel pressures of 1,200 to 1,500 PSI. Then compare those numbers to the original LB7 fuel injector that operated in the range of 4,500 to 23,200 PSI!

In Direct Oil Cooling – Part One, we discussed indirect and direct cooling methods and we examined oil’s new role as a coolant, rather than a mere lubricant, with new technologies such as under-piston oil squirting shifting more – up to 50% more – of the turbo diesel’s total cooling burden to the oil. We observed worst-case oil temperatures exceeding 360ºF, causing oil pressure to plummet and rendering oil, as a lubricant, virtually useless. In Part Two, we’ll look at the science behind indirect and direct oil cooling and discover why direct cooling, properly engineered, offers the only solution that can control:

Oil temperature,

Viscosity, and

Flow rate

to design specification limits under those same high load/high RPM conditions; and, substantially expand the overall capacity of the cooling system. In doing so, we will discover a host of benefits that can be realized only by directly cooling your oil.

Fact: As we saw in Part One of Direct Oil Cooling, GM has chosen to design and implement an indirect oil-cooling system for the Duramax engine. One result – other than living with scorching oil temperatures – of this OEM system that is not able to keep oil temperature under control during times of high combined work loads and high RPM is a host of after market solutions that promise to atone for the cooling system’s shortcoming. Unfortunately, many of them simply attempt to beef up the existing system with a bigger radiator or another fan instead of providing a solution based on a sound engineering approach that does not create undue burden on the overall system. That is, they continue to try, piggyback style, to cool the oil indirectly. While these would-be solutions may succeed in reducing oil temperature, for example, from 360ºF to (only) 330ºF, they do so at a great burden to the Duramax electrical system as well as taking a toll on precious fuel economy.

Suburban Renewal (Winter 2007), walked you through the upgrade process for a stock 6.5L using a representative Suburban 4x4. In that article, we focused reporting on the overall reliability and performance improvements realized through the upgrades. While these are, of course, vital to the everyday use of your truck, we will now focus on the uphill, heavy towing performance gains realized as a result of the upgrades. For many of us, this is what matters the most and it is during these times of high stress that we want to be able to depend on our work trucks. We took the time to test the towing capabilities at both the near-stock configuration and after completing our regimen of upgrades. Looking at the results, you will see that, with the right modifications, the 6.5L can comfortably “make the grade” and perform as a work truck should.

Our evaluation included the following level-grade tests measured in both elapsed time and distance consumed:

0-to-60 MPH Acceleration

40-to-60 MPH Passing Performance

The third test measured overall speed capability on a steady uphill six percent grade. During the tests we noted:

Engine Coolant Temperature

Exhaust Gas Temperature

Boost Pressure

Transmission Temperature