Engine choice is like your favorite flavor of food...... it is a personal opinion in most cases.
example.... international DT series engines dt360 dt 408 dt466 dt530 these are turbocharged, mechanical injection engines that have "sleeves". This means, to a point, the engine can be rebuilt in the bus.... or in situ. slightly cheaper for rebuild. I kinda like these engines. parts are around, they tolerate dirt better than a newer Electronic injection engine.. a DT466E for example is a newer engine with a computer driven injection system.
A DT360 and a cummins 5.9 on paper are a nearly identical engine from an engineering standpoint. With one major exception. Then engine block on the cummins is all piece and you cannot over haul the pistons/cylinders- which are called pistons/sleeves in the dt360. So a mechanical injection cummins has to come out of the bus to rebuilt. inline 6 a smooth running engine
a cummins 8.3 DT530 are the most similar to each other. both are about the same size 8 liters or 500 cubic inches inline 6 smooth running engine
a caterpillar 3116 and DT466 are most similar about 7.3 liters or 450 cubic inches inline 6 smooth running engine.
there are older Ford-New Holland engines 6.6 and I think 7.8 again both mechanical and inline 6
ford/international 6.9/7.3 idi indirect injection been around for a while not a power house but respectable... you are buying a bus, not an american muscle car. newer version 7.3 is again electronic injection but more power.
the weak point for all the international v-8's 7.3 6.0 6.4 what ever... is when they are turbocharged and the power turned up ... head gaskets. These engine use only 4 bolts around the piston. most of the others have five or six bolts.
the international 6.0 or ford 6.0 is had several problem areas and just doesnt have the staying power that the 7.3 does... in addition to the headbolt/ headgasket issue is camshaft lifters.... they come apart and that destroys the cam and that destroys the engine..... You have to completely take apart the engine to clean out all the metal bits ... It can do the job, but you will spend more in order to do this with reliability.
international 365 v8 same kind of issues with the 6.0 just has not gained a good reputation.
international maxxforce engines..... lawsuit lawsuit lawsuit terrrible terrible just dont. buy it and see about putting another engine in it
caterpillar 3116 3126 c7 the had more failures at lower mileage than the 3126. the 3116 is mechanical and the 3126 is electronic. The c7 engines last longer then the cummins 5.9 but about half the c7's failed at 590,000 thousand miles
the cat 3208 can be dependable bigger engine found in bigger busses... needs to have bearings replaced more often that seems to be the big weak point. again big v8 diesel found in older buses
detroit 8.2 v8 also know as "fuel pincher" this engine was the same era as the 3208 ford new hollands and cat 3208
cummins 5.9 half the engine failed at about 350,000 miles
then there are industrial gas bus engines ford dodge and chevrolet... international
yadda yadda yadda okay I am done for now.
Every engine, every transmission has a weak point. If These engines were such junk in the first place, they were not likely to have been made more than a few months.... read read read read... learn to filter out the opinions as stick to facts.
william call if you wanna talk bout engines 785 207 7600