If they are going 100k miles, they are probably using a bypass filter. With good enough filtration and decent additives(there are additives built into some bypass filters) you can run forever without a full oil change. There are a few documented occurances of trucks going over 1million miles without an oil change(although oil does have to be topped off periodically). I personally wouldn't take mine past 3k miles though with just a regular filter on.vindication said:20k huh? yeah you can do that if you get that crazy expensive oil that trucks use that last 100k miles. Even the Amsoil should be changed at max 15-17k, I'd change it every 10k with amsoil.
I change my oil and filter every 6k miles and I use castrol syntec
I haven't read the whole page yet, will do sometime tomorrow.
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