He puts his hat on. Marty speaks quite casually in the next line.
Marty: Oh Doc, I tore a hole in the gas tank. We'll have to patch it up and get gas.
Doc freezes and his expression changes. Something is wrong. Something Marty isn't aware of.
Doc: You mean we're out of gas?
Marty: Yeah, no big deal, we got Mr Fusion, right?
Doc: Mr Fusion powers the time circuits and the flux capacitor. But the internal combustion engine runs on ordinary gasoline, it always has. There's not going to be a gas station around here until sometime in the next century. Without gasoline, we can't get the DeLorean up to 88 miles per hour.
Marty: So what'll we do?
SEPTEMBER 4,1885
Cut to the area outside Hill Valley. The DeLorean is being pulled by horses. Doc and Marty sit on the roof. Doc has a whip in his hand. Marty is reading the speed off of Doc's digital speedometer.
Marty: Uh! Uh! Uh! Uh!
Doc: Ya! Ya!
Marty: (re: speed) 24!
Doc: It's no use Marty! Even the fastest horse in the world can't run more than 35 or 40 miles an hour. (to horses) Ya! Ya! Ya!
Cut back to Doc's shop. Doc is pouring some liquid into the DeLorean and Marty is inside it.
Marty: (re: liquid) Bartender says that's the strongest stuff they got.
Doc: Try it, Marty.
Marty tries to start the car, but it stalls. There is a strange noise coming from the back of the car.
Doc: Need more gas...
BOOM! The fuel injection manifold breaks off the back of the DeLorean.
Doc: Damn! It blew the fuel injection manifold. Strong stuff all right. It'll take me a month to rebuild it.
Marty: A month? Doc, you're gonna get shot on Monday!
Doc moves to a window. Outside we can see the railway station. Next to the window is a calendar with the date - September 4th 1885 - on it. Doc turns around to face Marty again.
Doc: I know, I know, I know! I wish..... wait, I've got it! We can roll it down a steep hill..... no, we'd never find a smooth enough surface. Unless..... of course..... ice! We can wait until winter when the lake freezes over...
Marty: Winter! Doc! Monday! It's three days away!
Doc: Wait. Let's just think this thing through logically. We know it can't run on its own power, and we know we can't pull it. But, if we can figure out a way to push it up to 88 miles per hour... huh?
Outside, we can hear a train whistle. A steam engine pulls into the station. Doc looks outside and spots it.
Doc: That's it!
Cut to the station. Doc and Marty are talking to the train engineer.
Engineer: How fast she can go? Why, I've powered her up to 55 myself. I hear that fearless Frank Fargo got one of these up to near 70 out past Verde Junction.
Marty: Is it possible to get it up to 90?