In the cartoon series, Optimus Prime most closely resembled a Kenworth K100.
Peterbilt produced cabover trucks primarily from the 1960s through the 1990s, with models like the 362 and 377. While exact production numbers are not widely documented, it's estimated that several thousand cabover units were manufactured during this period. The cabover design eventually fell out of favor in North America due to changing regulations and preferences for conventional trucks. Today, Peterbilt cabovers are considered classic and are sought after by enthusiasts and collectors.
Peterbilt truck
Peterbilt 379
Optimus Prime is the semi in the Transformers movies. He is a peterbilt 379.
Most of the newer trucks average around 6 mpg. My 1984 International Cabover with a 300hp BC3 got 5.5 mpg and my 1985 Freightliner Cabover with a 3406 310hp caterpillar got closer to 6 mpg. My 1996 Peterbilt 377 got a lifetime average of 7.3 mpg with a S60 Detroit 500 hp.
40 - 60 psi, depending on which engine you have;
Depends on your engine. Cats, Detroits, and Cummins all have their "sweet spots" - and they're not the same.
Cabover.
Peterbilt was created in 1939.
The more high end tractors are the Kenworth W900L, Peterbilt 379EXHD, Volvo VNL64T770 and VNL64T880, the International 9900ix, and the International Lone Star.
One can view the Peterbilt show trucks from the Peterbilt Motors Company and their website. Peterbilt is based in Denton, Texas and was founded in 1939.
You should probably be a little more specific. Transformers is a long standing franchise, and the cartoon series alone has several 'generations'. Traditionally, in the cartoon series, Optimus Prime was a red Cab-Over-Engine tractor (he was shown as a Peterbilt 379 bonneted tractor in the movies).