i have a 04 xterrra with about 77,000 miles on it and the oil light came on and the engine started to make a clicking noise. sounded like the cams at the top of the engine. i did about 90% highway miles on my truck and about almost 200 miles a day sometimes alittle more. i did get my oil changes done between 3,000-5,000 miles and i know that nissan says it should be 3,750 miles. anyways nissan says i need a new engine. says i have some sludge in my engine and they say that voids my warranty out for an engine replacement. they didn't even pull my truck into the garage at first before they decided it needed an engine. they went outside and started the truck up and said it will probly need an engine and they stuck with that. anyways i got an engine flush done with oil change and the oil light does not come on but it is still making the clicking noise but not as bad as before the flush. a friend said it might be a bent cam or some kind of lifter in the cam mechanism. any feedback would be apprechiated. thanks.