Maintenance Q&A
Upgrading again fleets and long-life coolant

By Paul Abelson, senior technical editor

Q. I’m an owner-operator who expanded my operation. I now have seven 2002 Peterbilt model 379s with the Cat C15 engine. A few of them are approaching 1 million miles, and we will have to start replacing them in the near future. As you are aware, that engine is no longer available in a new truck.

I looked at the new Peterbilt 579 and understand it is supposed to get better fuel mileage than my 379s. We are trying to decide whether to buy the 579 or 389 and whether to get the manual or automatic transmission.

Can you give any information on the fuel mileage and the tractor for the 2012 or 2013 model 389 and possibly 579? I’m not sure if the 579s are on the road yet. We are concerned about fuel mileage. Our trucks are for our own use, although we do try to get a backhaul to help offset fuel costs. We also want to make sure we get the truck our drivers want. We would consider the 587, but that would probably be low on the list.

A. At one time, Caterpillar was the engine to have if you were an owner-operator or small fleet operator. But as we all know, they decided to leave the over-the-road trucking market to concentrate on off-highway machines. That segment accounted for about 80 percent of their business. Now I’m sure it’s much more.

Part of the reason may be the trend to vertical integration by the truck makers who formerly installed Cat engines. Daimler Trucks North America owns Detroit. They make engines, axles and now automated transmissions for Freightliner, Western Star and Mercedes trucks.

Volvo Group makes most of its own engines and some transmissions for their two brands, Volvo and Mack.

Paccar makes engines for Kenworth and Peterbilt, and Navistar makes engines for its International brand.

Cummins engines are now available in some International models and for big power in Kenworths and Peterbilts. Cat’s former customers narrowed the market opportunities for Caterpillar engines by adding proprietary power.

Pete’s 579 shares some of its cab structure with the old 379, but it is wider by about 10 inches. The aerodynamic enhancements are dramatic. The 579 package should be good for around a full mile-per-gallon improvement at highway speeds, when compared to the 379.

The Eaton UltraShift Plus automated manual transmission (AMT), available from Peterbilt, is a tried-and-true transmission that has had some dramatic electronic programming enhancements.

I was first exposed to AMTs a dozen years ago when a friend ordered his new show truck. At that time, he was a 3-million-mile safe driver. I was very surprised that such an “old pro” who could float gears with the best of them would buy an AMT. As I drove across the hills of I-44 crossing Missouri, he pointed out many of the transmission’s features.

The first thing the truck’s owner mentioned was that his right shoulder and left leg didn’t hurt at the end of the day.

As experienced as he was, he rarely missed a shift, but the AMT never missed one. When I was on a 6 percent downgrade almost a mile long, I would never think of trying to downshift with a regular gearbox. With the AMT, I was able to stab brake and go down a gear – twice. The third time I tried it, the engine and transmission were out of range of each other. Instead of hanging me out in neutral, the transmission just stayed in gear. It would not start a shift it couldn’t complete. That, to me, is a great safety feature. I found I didn’t spend much time at all worrying about matching speeds and gears. That left me more time to pay more attention to traffic.

With AMTs, shifts are smoother, causing less wear and tear on the entire drive train. Because shifting is computer controlled, fuel economy is improved. The newest Eaton UltraShift Plus models available on Peterbilts have creep control and hill hold – both useful convenience and safety features.

If you haven’t already guessed, I’m a big fan of automated transmissions. They pay for themselves in just a few hundred thousand miles, leaving you the balance of the million miles you keep your trucks to put money in your pocket.

Fuel mileage has many variables, so I hesitate to comment about what you can expect, other than to say that the laws of physics dictate that a more aerodynamic 579 will be significantly more economical than an identically spec’d 389. From all that I’ve heard to date, drivers love the new Petes.

Q I recently bought a 2006 Freightliner Coronado with a 500 horsepower Series 60 Detroit Diesel engine. It had about 625,000 miles. I had a mechanic change all the fluids and check all the components because the maintenance records were sketchy. I got a good price because of that. And so far, I think I’m ahead even with the mechanic’s charges. When he drained the coolant, he said it looked cloudy. He replaced the green coolant with orange because he said it will last about as long as I intend to keep the truck (about 1 million miles) or longer if I put in a booster.

My questions: Why was the coolant cloudy, and will changing the coolant to the new type fix the problem?

A. It would have been nice to have had a coolant analysis done, but it’s too late now. I consulted with Carl Tapp, one of my brain trust members. We agreed that the cloudiness was likely because of poor maintenance of the cooling system. The previous owner probably said, “Change the oil and if it runs, leave it alone.”

By draining and upgrading the coolant, your mechanic did the right thing. With long-life coolant, maintenance will be minimal.

We recommend that you do oil analysis at your next few changes. Plot the results for the major wear metals on graph paper and see if any trends develop. That will let you know the health of the engine.

Keep checking your coolant for traces of oil or sludge, just in case. Be careful that you top off the coolant with only the new extended-life coolant. The older style coolant will mix without harming the engine, but you’ll lose all the long-life advantages. LL