Graymist, I don't know that there is a minimum number of miles you must have on oil before you can get an accurate reading, but I prefer checking at the time I do an oil change, which is usually around 15,000 miles. I would think it would be best to have at least 5-10M miles on the oil.

 

They should be able to tell if you have excessive wear on certain bearings from their analysis. I also like to have a historical view to check and see whether things are getting worse. They know, based upon historical data, that metals should be at a specific level with a specific number of miles and with each brand of oil. If your level of copper is high, then you may want to check further before there is a system failure.

 

I see what you're saying Gman. But under practical circumstances, when going in for a used truck purchase, how realistic is it to expect the seller to provide oil sample test results going back a few months ? Would you, as in yourself, buy a used truck where you had the results of only one such test to go by, that being the one you that got done yourself ?

Also, as for dyno testing, how long does it take to obtain a report ? Is there any such testing available for other components like the tranny, electricals, & suspension & frame ?

 

I would rely on a single oil analysis when looking at a used truck. Most sellers will not go to the expense of an oil change when they are ready to trade or sell. You can still tell a lot about what is going on inside the engine with an oil analysis. The dyno can usually be done in a few hours, depending on how busy the shop may be at the time. They dyno itself should not take that long.

I don't know of a similar test for the tranny, etc., However, you can pull the inspection plates from the rear power divider and rear end. You could get a magnet and put it in the bottom to see if there are any pieces of metal. That could be a sign of some potential problems. Springs, frame, etc., will need a visual inspection and a good mechanic can usually spot any problems. You can easily check spring hangers, shocks, etc., Kingpins are good to check. You can pay special attention to unusual tire wear. That could alert you to some potential problems. If you find a truck that you really want to buy just driving it and a visual inspection can tell you a lot about what the mechanical is likely to be. One inexpensive way to check the truck is to have a DOT inspection performed at a qualified shop. They are usually good about spotting things to do with safety. If you are not mechanically inclined, I suggest either taking a mechanic with you or a shop and have them check it over thoroughly.

One other inexpensive check you can do is have a qualified mechanic hook up his computer to the truck's cpu. It will give you a good history. This should be done for around $40 or less. This only takes a few minutes. The shop can usually give you a print out on the spot.

 

Graymist, I recently bought my used tractor with only an oil anaysis that I had done during the drive home. Some of the readings will tell you if an obvious problem exists even with only one sample/analysis. Maybe you could take your own sample before you agree to buy and make the purchase. Get the results, then make your final decision. In my case, I had the truck inspected at a dealership in the town where I bought it, the seller was a small dealer with no shop and he let me take it to a KW dealer at my expense to have a pre-purchase inspection done. During the inspection, the dealer removed an oil sample for me which I took with me and had anazlyed later. The shop also hooked up to the truck's computer and printed all the data for me.

 

The differance between a lab oil sample and speedco ....

At the lab the run it through a filter that can change red wine to white wine ( seen it done @ Fabic Cat in Fenton, Mo )

Oil analysis is more controled over time ( more samples ) but a single sample can tell you alot if you have a few details.... ( miles on engine and as close as you can miles on oil ) if the dealer changes the oil before he sells it I would run away!!!!!!

I dyno and oil sample every used piece of equipment I buy and recommend it to every one....

Most dealers will foot the bill if you agree to purchase if it passes.... I have had a few hard heads and I get them to agree in WRITING that if it fails a dyno then they pay if it passes I pay