I have a question about engine cruising RPM vs engine wear. The new car I am buying is a 5 speed manual...

I have a question about engine cruising RPM vs engine wear. The new car I am buying is a 5 speed manual, and at highway speeds it runs at about 4000 RPM. I am used to my older 6 speed that cruises at half this RPM on the highway, so 4000 seems high. I do a fair bit of highway driving so I am wondering, will an engine that cruises at 4000 RPM on the highway face more engine wear than one that cruises at 2000? Or am I being irrational and worrying for nothing? The engine uses 0W20 oil if that matters.

No but more fuel.

In theory anything under the red should be fine for the engine, but I'd imagine in practice faster rotation means higher wear.

Source: my ass

Doesn't matter even a little bit. Economy cars of '80s-'00s, and to a lesser extent today, frequently turned 4,000rpm going down the highway. They did this by design, for twenty years and hundreds of thousands of miles, without complaint.

Not necessarily, even though the engine is spinning faster it is at a lower load % and uses less fuel per rotation

I used to think that RPM = fuel consumption but it is actually a lot more complex than that

Engines have an optimal wear zone. 4000rpm is getting pretty close the the edge of that zone. There's a reason why commercial and industrial engines are big and low rpm. I'd be more worried about your ears having to listen to 4000rpm for hours on end.

Im just going by my own shitbox 5 gear that soins at 4k
City driving consumes less fuel than highway.
Our golf 7 tdi lasts much longer

my shitbox is between 3500 and 4k when im on the highway and it gets 30 mpg all day. these little motors are made for it. 130k miles and counting still running fine

I accidentally shifted from 5th to second and the RPMs shot up to 7000 but 1500 below red line. Is my engine kill?

No

No, it doesn't even have to be kill even if it went past the redline if you could just keep driving after

Noice.

meh, my daily runner does 3500-4k rpm on the highway, no probs. the manufacturer knows in what window the engine will spend a lot of time if they couple a gearbox with those ratios to the engine.

Dont worry about it. Just change your oil and transmission fluid regularly and you will be good to go.

always wondered why is that, after all as the engine builds revs it also build inertia, so a fast turning engine should continue turning while using less fuel, or no?

I wouldn't worry about it.

If it overreved, yes your engine will be damaged.

But since you said it didn't, it should be fine. Synchros might have gotten more than average ware kek

its not bad for the engine, but you might not enjoy it

it is more complex than that, but there is a tendancy. higher RPMs don't correlate 100% with increased fuel consumption, but if you are revving significantly higher, the higher number of combustion will generally equate to more than the decrease in fuel per combustion.

Hence people getting worse mileage on the hwy when they put a different diff and their cruising rpms go from ~1,800 to like 3,000.

Example: see how your fuel usage compares going 100 miles at 60mph in 4th gear and then in 5th gear.

I thought the exact same. Even after learning all these years the best simple answer I can come up with is "it depends".

Is it an ITR? I drove one for a week, b18cr revs like a motorbike. I was cruising everywhere at 110km/h and doing just over 4K and barely noticed. Even if the cabin noise gets to you it's worth it for the super aggressive diff for when you want to chop 3rd and pass that v6 commodore

if the engine is healthy, its fine, if theres any underlying problems, itll show up fast. my Toyota Crown ive gone down the highway at 5000rpm for hours at a time, never an issue since its a healthy engine. my Subaru Sambar 50km of highway after i bought it from the guy i was crusing at 100kmh probably 5000rpm uphill and the thing quits, waterpump seized because nobody ever changed it and shredded the fucking timing belt lol

the stroke length of the pistons also plays into it

How fast are you guys driving on the highway?
My 99' corolla rides at 3k going 78mph in 5th gear.
4 grand is 101mph and this thing is a pice of shit car.
My 94' Tercel is a 4 speed and would be at 83mph at 4k,

2002 yaris 120 km/h at 4k rpm.