Truck Repair: Check Engine Light, cat engines, mile trips

Question
I recently purchased a retired 1988 U-Haul GMC 6000 with a large block Cevvy engine which is performing nicely enough though a bit rough on gas mileage. It gets ~5.3 mpg loaded and ~5.9 empty on long (greater than 300 mile) trips.

The check engine light is on. What should I be doing about that? The truck has ~143,000 miles on it and other than a really noisy manual transmission I find no fault with it.

Answer
there are many reasons for the engine light to come on.
you really need to have the engine scanned for codes. some CAT engines allow you to count the engine light flashes to read the codes. turn on the key, set the cruise switch to on and push the set button for 10 seconds then release. the engine light should start to flash.

flash,flash......flash,flash = code 22

write me back if you get a code. good luck    Rusty