Maintenance Q&A
Updated oils in a restored ride

By Paul Abelson, Senior technical consultant

I recently bought a 1982 Peterbilt 359 as a restoration project for me and my oldest son. It has a Cummins 400 horsepower big cam motor, an Eaton Fuller 13-speed overdrive transmission, and Rockwell 3.90 rears.

There have been a lot of improvements to oils, greases and filters in almost 35 years, so I want your advice on what to use and how often to change things so I won’t be spending money on things I don’t need.

What a great family project. When I called to get some more information, you said you would be pulling a platform trailer in parades and to truck shows but not doing any real hauling.

You are right that oils have improved tremendously in the 34 years since your truck was new. Your engine required 15W-40 CD oil for turbocharged diesels when it was built. The current spec is CJ-4. It will keep your Cummins rolling smoothly for far longer than the 10,000- to 12,000-mile drain interval most drivers used back then.

Unless you’re especially active with the truck, taking it all across the country, you should be able to go up to six months between oil changes on today’s improved mineral oils. Even then, I would only change it because oil can oxidize into sludge over time. Synthetic oil will go a year in limited use. It has much better oxidation resistance, but is much more detergent than mineral oil. Use it only after you have torn down and rebuilt the engine.

If you drive the Pete more, you could consider changing oil at 18,000 to 20,000 miles, with filters and a chassis lube halfway to your oil change. Greases and seals have improved so that 6,000-mile chassis lubes are no longer needed. When you do your restoration, be sure to upgrade to the most modern seals. Check with your grease supplier for their interval recommendation. The same for engine oil seals.

Fuels have gone from 5,000 parts-per-million (ppm) sulfur to only 15 ppm. With today’s engines having fuel injection pressures greater than 30,000 pounds per square inch (psi) compared to your big cam’s 2,000 to 3,000 psi, any filter that will fit on your engine’s filter mounts will provide superior protection.

Make certain that you have a fuel-water separator, built either into a fuel filter or as a stand-alone unit. Since your truck may be sitting for weeks between events, water will condense from the air in the fuel tanks. If it gets to an injector, the water can suddenly expand with explosive force, driving the tip into the aluminum piston crown. After each outing, be sure to drain all accumulated water from the separator’s reservoir.

Back in the day, truck engine tolerances were measured in thousands. Oil filters remove contaminants as small as 25 to 40 microns, or 0.001 to 0.0015 inches. In order to allow oil to flow freely, primary or full flow filters haven’t changed their filtering sizes, but the materials they’re made from have improved. As filters plug, their efficiency improves, but their ability to flow oil decreases. The ultimate example is a fully plugged filter that blocks 100 percent of all contaminants but doesn’t allow any oil to flow.

To delay this plugging, bypass filters like the Luberfiner you got with the truck take about 3 to 5 percent of the oil and send it through densely packed fibrous material to remove contamination as fine as 1 or 2 microns. This ultra-filtered oil goes directly back to the oil sump, bypassing the engine’s lubricating system. Many companies’ filter elements will fit in your 750-cubic-inch housing. If you use one, don’t forget to add additional oil to fill the canister each time you change oil. Change filter elements every time you change oil.

With the new synthetic gear oils made today, your transmission and drive axles should be good forever if you switch over. Good luck on your project. I hope to see the Pete at a truck show someday.

With all the talk about corrosion, I never see anyone suggesting undercoating. Back in the 1960s, you paid extra but got this great coating underneath any vehicle, car or truck, which kept the bodies from rusting. Why don’t we just go back to that?

There were many reasons we stopped applying the old asphalt-based undercoating. First of all, demand fell when vehicle manufacturers switched to galvanized steel and other pretreated materials that successfully controlled rust. Undercoat material required a good amount of volatile organic compounds or solvent to allow the tar-like mass to remain pumpable and sprayable. The EPA set limits on volatile organic compound emissions, further reducing demand. And few operators wanted the added weight of a fully undercoated truck, especially an undercoating made with rust-resistant asphalt.

Then came the combining of salts and other chemicals and the corrosion crisis we’re facing today. That inspired innovation and improvement as crises usually do.

There are undercoatings available, but you often have to look long and hard to find them. I’ve heard truck salesmen say that their trucks are made from rust-resistant materials and don’t need undercoating, especially when they’re trying to beat a competitor’s price.

Today’s undercoating has improved. It’s now applied at less than 20 mils thick (0.02 inches) compared with five times that or more with the old high-volatile organic compound undercoat. It’s reasonably light and cost-effective.

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