Whereas the 1938 Grand Prix single-seaters had a swept volume of 3,000 cc, the new ones had supercharged 1,500 cc engines or 4,500 cc, unblown engines. For motorcycles, supercharging and special fuels had been prohibited. The 188 km/h (117 mph) fastest lap made by Sanesi with an Alfa Romeo in the automobile Grand Prix, and especially the lap averages made in the motorcycle Grand Prix - 177 km/h for the 125 cc, 144 km/h for the 250 cc, 160 km/h for the 500 cc - showed that the new road circuit had to be considered faster than the "Florio circuit" of 10 years before. With its renewed facilities the Autodrome was host to all the events between 1949 and 1954. During this period accommodation for the public was in particular improved with small covered stands on the outside of the second "porphyry" bend and the second Lesmo curve. Other small stands were installed at the "porphyry" bends while a number of boxes were built for the public on the roof of' the refuelling pits.
The 6,300-metre road circuit witnessed numerous formula changes for Grand Prix cars with the 1,500/4,500 cc Formula 1 up to 1951, the 2,000 cc Formula 2 in 1952 and 1953, and the new 2,500 cc Formula 1 in 1954. For this reason it is difficult to evaluate the technical and functional developments of these cars on the basis of performance at Monza. Contrarily, motorcycling results are a clear indication of the increased speed achieved, first by progressively increasing specific power, and second, mainly by having continuously more complete recourse to aerodynamic fairings. In 1954 general averages rose to 146 km/h (90 mph) for the 125 cc bikes and nearly 180 km/h (112 mph) for the 500 cc class.
In the meantime the activies of the autodrome had been enriched by a number of events including the Inter Europe Cup for Touring cars introduced in 1949, the Autodrome Grand Prix reserved for Formula 2 single- seaters (except in 1953 when it was run with International Sports Cars), and it was sometimes coupled with the Monza Lottery. In 1954 Lottery prizes were awarded according to the outcome of the Supercortemaggiore Grand Prix, a 1,000 kilometre (620 mi) race sponsored by Italy's major oil company and reserved for Sports category cars up to 5,000 cc. This race was won that year by Mike Hawthorn in a Ferrari and the second year by Jean Behra in a Maserati.