Recommendations?

So im in the market for an ecodiesel reason being is i want/need a fullsize truck that gets good gas mileage on the freeway and have a family of 4. I commute to the next town over 5 days a week not including overtime. Its a 60 mile trip each day. My budget is being about 20k. Im located in California and all the used EDs are about 15-20k but all with 100k-170k miles. Would you recommend getting a high mileage one depending on service records?