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Reader: Thanks for the good article on extended oil drain intervals ("Willie's Workbench," June '07). I am a mechanical engineer by day and wanna-be gearhead by night, so this area is fascinating to me. I have a '96 Dodge Ram 2500 4x4 with a 12-valve Cummins turbodiesel, and the truck currently has 279,500 miles on it. After a break-in period of 15,000 miles or so, I switched to Mobil Delvac 1 synthetic 5W-40 for diesel engines, and began sending a sample of the oil to U.S. Oil in Combined Locks, Wisconsin. I did this on the advice of a mentor/buddy who runs and maintains a fleet of tour buses in the Chicago area. They use oil sample analysis for predictive maintenance. I made a point of sending an oil sample, taken from a drain valve in the pan with the engine hot, every 5,000 miles, and at the same time installing a new Fleetguard filter filled with a quart of new oil.
For $12, U.S. Oil sends me a report from their analysis, which I believe uses mass spectroscopy to measure the levels of various metals, contaminants, and components of the oil itself. The main categories that concerned me and my Cummins engine were the iron, chrome, copper, and aluminum wear metals, in addition to the silicone, fuel, and water levels. The wear metals indicate which engine components are wearing or damaged (iron = cylinder liners, chrome = rings, copper = bearings, aluminum = pistons). U.S. Oil has compiled a database of results from many engines, and they give warnings or other comments based on the levels of those items in the sample analysis. For example, if the silicone levels are high, I would probably check or change my air filter; if the fuel or coolant levels are high, I would check for a blown head gasket; and so forth. I never saw the iron content go over 50 ppm, at which point U.S. Oil indicated it might be time to change the oil. I routinely drove for a calendar year on a single oil change, or between 25,000 and 35,000 miles per year.
Given that my engine has never been apart, except for fuel pump upgrades (currently dyno'd at 350 rear-wheel hp and 890 lb-ft), the program to which I adhered certainly kept my engine in good working condition. I have tried various oils, including Mobil, Lucas, and now Amsoil, all of which yielded similar results and fuel economy. I can't say that I saved any money versus using mineral oil and changing it every 3,000 or 5,000 miles, but on the other hand, I have never had any failed parts.
New Albany, IN
Reader: I am the mechanic for Skamania County's (Washington) fleet of vehicles, which includes our Sheriff's Department pursuit vehicles, as well as the Road Department's snow plow pickups. I am in charge of the maintenance and repairs of about 120 vehicles, all with gas engines. The debate about when to change the oil is always controversial, so my answer is to go with 3,000 miles as most manufacturers recommend. This does two things. First, it covers me, but for liability issues, if anything should go wrong it would be documented that I serviced them at the correct intervals. Secondly, it's my feeling that with a fleet of vehicles such as ours-especially police pursuit vehicles-changing the oil is only one part of inspecting the vehicle at regular intervals to make sure everything is in top condition, e.g., the tire tread, brakes, lights, and so on. So to me, it is more a matter of seeing them on a frequent basis to make sure nothing else is failing.
As a note, in my 12 years working here, we have only lost one engine in a fleet of 120 vehicles-pretty impressive considering how many miles get put on them in so many years with so many different drivers and conditions.
Editor: Willie's essay on oil-change intervals sparked more reader responses than any other story that's appeared in Four Wheeler in the past five years. Sometimes, it's the small things that make the biggest impact on folks. We forwarded all of your messages to Willie, and while he likely can't reply to every one, we're sure he'll be checking in again one day with more on this always-timely subject.
And we're definitely believers in oil analysis. Our own Jimmy Nylund had the oil in his brand-new Silverado pickup (with only 1,300 miles on it) analyzed for the September '06 issue, and found that it was nearly as contaminated-more so, in some instances-as the used oil that he runs in his high-mileage Jeep-based tractor. Thanks to all for writing in.
Reader: Your review of the new 54-inch TSL Bogger (June '07) contained a mistake in the specs. You stated that the tire turns 104 times per mile. That is off by a factor of four, for some reason.
The circumference of a circle = f d, and given a static loaded radius of 24.25 inches (according to the mag), this yields a 152-inch circumference. Divided by 12, this yields 12.7 feet. Now, 5,280 12.7 = 415.75 rotations per mile, not an amazing-sounding 104. For the tire to only turn 104 times it would have to be a 194-inch-tall tire-and I seriously doubt it's that big at 55 mph.
Editor: Well, you're off a wee bit too (the actual overall diameter of the TSL is a smidge over 51 inches, not the 48.5 you used to arrive at a 152-inch diameter), but heck, you're obviously a lot closer than we were. The guilty party has been remanded to his junior-high geometry class for a refresher course . . . and thanks for keeping us on our toes.
Reader: Being a subscriber to your magazine, I saw the start of your Project RangeRunner. I thought, "Wow, long travel and four-wheel drive." Well, I sold my 4x2 Tahoe and bought an '04 4x4 Ranger. All I knew is that the Dixon suspension kit had to be purchased from them in California, and I live in Las Vegas.
Another part of this was the fiberglass fenders. I visited Glassworks' site and saw that there was a Las Vegas dealer that sells the fenders, Woolworth Motorsports, so I gave them a call. I asked them if they had heard of the Dixon Racing long-travel kit for Rangers, and they replied with, "Yeah, we have three Rangers here at the shop with the kit on them." I got a price, and then went down to their shop to check out the kit installed on their shop truck. It was the coolest thing I ever saw! We worked out a price and the parts got ordered. I found out that you can't just go pick this up-you have to wait. The kit finally came in, and my life was changed forever
I have the front end done, with Fox Shox remote-reservoir coilovers, and I had them weld in the bumpstop cans so I can easily add those in the future. I went with Mickey Thompson Classic Locks and 33-inch BFG Mud-Terrains.
After getting a taste of it now, I am saving for the rear to get done. I started a new Web site to help promote the sport, and have been going to all the races from SNORE, BITD, and so on, and I am waiting for the Las Vegas CORR race this year. I wanted to tell you how your project changed my life and thank you. It has been a lot of fun so far.
Adem Martin del Campo