MTBF

First, dont shoot me if this topic is in the wrong section!
I've been wondering, i am trying to make reliable engines with some power, but the highest mtbf wich i get is 65k to 75k MTBF. (i am using inline six and V8's for this)
is this high or low? and what is a nice MTBF to aim for?
and last but not least, whats the MTBF of RL cars?
I've been wondering, i am trying to make reliable engines with some power, but the highest mtbf wich i get is 65k to 75k MTBF. (i am using inline six and V8's for this)
is this high or low? and what is a nice MTBF to aim for?
and last but not least, whats the MTBF of RL cars?