Back to the Future- Marty wakes to a new future - question

At the ending of Back to the Future, Marty says he’s not going to the lake as the car is ‘wrecked’. All tha family react as if he’s taking about the BMW. They rush out and see it is fine.
But they know Marty has the Toyota truck- why would they not think he meant his car is wrecked’?
I know he says car not “truck” but he’s talking about going up to the lake- he wouldn’t be going in his Dad’s BMW.
So is this a mistake or bad script writing?

It’s not a mistake, nor is it bad writing.

In that scene, the rest of the family knows that Marty has a truck (because they only know the reality of the “new” timeline), but Marty doesn’t know this yet; in the original timeline, when Biff was still bullying his dad, Marty doesn’t have a truck.

Early in the film, we learn that Biff had borrowed, and wrecked, the McFly family car (which is what Marty would have driven to go to the lake with Jennifer). And, there’s also an early scene in which Marty fantasizes about someday owning that Toyota truck.

When Marty returns to 1985, he doesn’t realize that the timeline had been changed by him helping his future father find his courage, and, as far as Marty knew at that moment, the family’s car was still wrecked. And, when he says “the car is wrecked,” they assume he’s talking about the BMW.

Yeah. He’s not thinking about the new vehicles.

So the question has to do with the rest of the family’s reaction (which I don’t exactly remember after all this time), not Marty’s expectations. If, in fact*, they all rushed to look at the BMW, then this reaction doesn’t match what they are supposed to know about the current McFly car situation, i.e. Marty having the truck.

*I really don’t remember this one way or the other.

Right, but the question that the OP is asking is what the rest of the family is thinking (when he says that the car is wrecked), not what Marty is thinking.

That is what I’m asking about- the family’s reaction didn’t make sense. They rush to look at the BMW. Marty did not know yet about the Toyota and that no car was wrecked.

BTW, for reference, here’s the dialogue from that scene (source):

They’re talking about the new car. They don’t know Marty’s reality.
He doesn’t know theirs.

It makes perfect sense. Marty says, “the car’s wrecked.” They assume he means the BMW, because, in their minds, if Marty meant his vehicle, he would have said “truck.”

They aren’t putting two and two together as you suggest (“why would Marty be talking about the BMW? He has his own truck, and that’s what he’d be taking to the lake!”); what we see and hear is their immediate reaction to Marty giving the shocking (to them) news that “the car’s wrecked.” That’s all.

The real question is what happened to the ‘Alternative’ Marty; the one who grew up in this timeline and with whom the other characters are familiar, who was suddenly and inexplicably replaced by ‘Prime’ Marty?

Stranger

Same Marty. The time travel is never all that consistent in the movies.

It’s like what happened in the 50s. Once the changes to the time stream catch up, he gets caught up in them, too. In the 50s, that means he might never have existed, so he would eventually fade from existence. In the new timeline, it means his memory will eventually catch up to the new reality.

Apparently, this happened to future Biff in the sequel, according to the filmmakers. After he went back to make his younger self a millionaire, this resulted in a future where he didn’t make it to old age and he started collapsing when he got back to 2015

I’m with the OP on this, it does feel a little off, but then again it’s a time travel film, and as Stranger has just mentioned, plot holes occur as they always do with time travel films. It’s still one of my favourite films ever. It is fun to discuss all the inconsistencies though.

There are timey-wimey things that don’t line up. The car issue at the end is easy.

Or, why did McFly hire the attempted rapist of Lorraine for things like waxing the car?

^^^ This is my question. How can she be okay with having this proven sleazebag around, tamed or not? He sexually assaulted her. Then he got his ass kicked, okay, but still. No way she wants to see him working in the driveway, no matter how much he’s groveling.

There’s only one thing about the new timeline that bothers me, and that’s why they have such a crappy house when they’re such a successful family.

The only way it works to me is if Biff winds up in jail, shows himself actually reformed, an the it’s Loraine herself who has compassion on the ex-con and chooses to hire him.

And, yeah, while I agree the OP’s logic makes sense that they’d think Marty was talking about his truck, it could be that new Marty just always refers to his truck as a truck and always used “car” to refer to the BMW.

Edit: and the house could be something passed down that they kept for nostalgic reasons.

I seemed to me that there were …”context clues”?…that the house was changed also. It was the same house, but now was airier, lighter, more open and well maintained instead of being slightly run down and had perhaps unseen features such as maybe a tennis court that were not hinted at in the original timeline. Much like the McFlys

Look at it this way:

This is a two-car household. If the car is wrecked and Marty takes the truck up to the lake, then the rest of the family won’t have any way to get around. So, the family just thought Marty was saying
“We talked about this. We’re not going up to the lake. The car is wrecked [so you’d have no way to get around while I’m gone]”
“Wrecked! When did this happen…”

Though why only two cars? What did Marty’s brother or sister drive?