If it was not for bad luck I would have none at all!

heres what I would do, an older mechanic told me this that has delt with low budgets before although it may not be right in some peoples eyes it has worked for me

1)check the oil pressure with a mechanical gauge

2)if its low drain the oil

3)refill the oil with diesel fuel or furnace oil this cleans and will lubercate some insted of running a solvent through it

4)run for 1-2 minutes and drain

5)repeat until its clean, drain and make sure all diesel is drained

6) change oil filter and refill with quaker state