Wow what a discussion,
Can i add a few curve balls too!
I think it is to do with air speed or engine rpm and also piston materials used.
My ford 3000 tractor is about 30 years old, and has an oil bath filter and still starts with out glow plugs. Cast iron pistons, and low rpm/ air speed. Think of all the dust when plowing.
My son has a 2005 model dirt bike with the best filter you can buy. Last month he rode in dusty conditions for 45mins with the air cleaner not fitted correctly and dusted his engine. Now it will only roll start. No compression and time for new piston. Alloy piston/14'000 rpm and a 1/4 inch gap under the oil filled foam filter and engine destroyed in 45mins.
In short, i think newer vehicles rev harder, have greater air intake speed. The engine materials are lighter alloys and not as durable and tolerances are less so a better air filter system is required so 'horses for courses'.
All the best
James
