When I was a young person most car did not have fuel injection and I was told it was a good thing to go out on a highway and " blow out the carbon from the engine".
Is this still a good thing to do ? If so, how often and for how long ?
The ol’ Italian tuneup was only ever really (maybe) useful if you had a car that mostly got used for short trips at low speeds. With modern fuel injection, carbon buildup shouldn’t be a problem, but if you do have a “couple of blocks to church every Sunday” type car, it’s not a bad idea to do a bit of highway driving occasionally to drive out any condensation and light hydrocarbons that might accumulate in the oil. No need to run it at top speed or anything like that. 5-10 miles of normal warmed up highway driving ought to do the trick.
Italian Tune Up? No really needed anymore, with modern additives. But if you make lots of short trips, where the car never gets up to ideal temperature, might not be a bad idea to let her gallop once week or so.
Edit: got greased by Jack.
There are products available these days that will handle the problem better than trying to run the car hard enough to burn the “junk” out. One of the best is a foam from Mopar, Mopar Combustion Chamber Cleaner.
Over here, diesel engines have a particle trap which needs a good run to get it cleared out. Anyone using a diesel engined car for short runs is advised to take it for a sightseeing trip once a week or so.