Since Rochester filled it up, let’s assume it was near empty. Jack only put in a gallon or so at a time. How large is a Maxwell’s gas tank? Any car buffs?
Assuming Jack Benny would have sent Rochester to the cheapest gas station around, let’s assume 20¢/gallon in the mid-'40s. If the total was $2.80, then that comes to 14 gallons. Again, I don’t know what a 1908 Maxwell Roadster’s fuel capacity is; but 14 gallons seems a little much for a smallish car. (For comparison – kind of – my '66 MGB has a 12-gallon tank, and my '46 Willys CJ2A had a 10-gallon tank.)
But what if it wasn’t right after the war and was in the '50s instead? If we assume a quarter for a gallon, then that’s 11.2 gallons. That seems reasonable. But since it was a gag, the number of gallons isn’t as important as the amount Rochester spent.
That would depend on which model, undoubtedly. Maxwell was actually a fairly popular make in the first couple decades of the 20th century. They were made from 1904 to 1925, and the company produced several models:
On radio, they probably didn’t establish which model Benny drove. The wiki article on Benny indicates that they used two different ones when he moved to televison, and he probably used different models for promotional appearances, not just the 1908 roadster in the pictures:
One of the Jack Benny commercials from the early 70s had service men singing “Won’t you fill up, Jack Benny,” done to the tune of “Won’t you come home, Bill Bailey.” It ended, of course, with Benny singing, “I’ll take a gallon.”
The writers were never consistent what year or model Maxwell Jack was driving. In a late 1930’s show, Mary Livingstone chides Jack for still driving a 1920 Maxwell. as the show went on, the Maxwell became older and older, where a 1908 model would have been more consistent with the description given. (The Maxwell that jack was shown driving in It’s A Mad, Mad, Mad, Mad World was a restored 1923 model, inconsistent with the bone-rattling deathtrap Jack drove on his show.) Having said all that, Jack was so cheap that any price paid for gas would have been outrageous.
It’s a cameo early on, I think, because it’s still in the desert. The bunch of them are arguing about something, he pulls up in his Maxwell to ask if he can help. When they refuse vehemently, he does his patented “Well . . .” and drives off.