[dawrr]

On the highway, I usually go 65 mph (the speed limit around here).

Most other people go 75-90 on average.

Once in a while, I need to get up to 75 to avoid merging-related accidents. Yeah, people around here just don't know how to merge.

So, my question is, is cruising at 3000 for extended lengths of time going to ruin my engine? What rpm would you say is the "cutoff" mark for cruising. I don't drive for hours- maybe an hour at most. Usually 20 minutes.

[EagleAutosports]

3000 isn't too bad. You'll be alright. And I know about people wanting to fly when they're not going anywhere.

[dawrr]

Originally Posted by EagleAutosports

3000 isn't too bad. You'll be alright. And I know about people wanting to fly when they're not going anywhere.

What about 4000? I know a guy at my college who has 4.56 gears in his V6 Automatic. He claims he cruises at 4000 on the highway. How long do you think he'll be able to do that for?

The dampener should take care of vibrations up to around redline, right? And at such speeds, the airflow cools everything down well. So what else busts at high rpms? Call me stupid, but I want to know this.

[EagleAutosports]

4000? I've heard of that before and can we say no gas mileage? I wouldn't want to do it on a consistant basis, like in a daily driver.
Yes, the damper should control harmonics up to 6000 or so and the main parts that would fail with consistant high rpms would be the valvesprings due to metal fatigue.

[dawrr]

Originally Posted by EagleAutosports

4000? I've heard of that before and can we say no gas mileage? I wouldn't want to do it on a consistant basis, like in a daily driver.
Yes, the damper should control harmonics up to 6000 or so and the main parts that would fail with consistant high rpms would be the valvesprings due to metal fatigue.

Interesting. That's what I thought, but I've also read about how a few people on here hold their engines revved at 3500 for 10 minutes.

I'm looking at it from a different perspective. Moving stuff wears out faster than non-moving stuff in most cases.

[markwondi]

RPM is a relative rate for the fatigue limits for materials. The engine was designed to run below those threshholds so that the engine won't break parts due to fatigue (called fatigue limit).

You'll be perfectly fine at 3,000 rpm.

[dawrr]

Originally Posted by markwondi

RPM is a relative rate for the fatigue limits for materials. The engine was designed to run below those threshholds so that the engine won't break parts due to fatigue (called fatigue limit).

You'll be perfectly fine at 3,000 rpm.

Ok cool. I was just rethinking the gear decision. My gas mileage really didn't change at all, but I didn't want to kill my car. I rarely go over the speed limit, and if so, it's usually minuscule.

[markwondi]

Originally Posted by dawrr

Ok cool. I was just rethinking the gear decision. My gas mileage really didn't change at all, but I didn't want to kill my car. I rarely go over the speed limit, and if so, it's usually minuscule.

Run it hard, run it forever... it'll be fine

[8fo5ohgeetee]

It might be wise to install underdrive pulleys if you're running 3000+rpm's a lot. Not only will you get a bit more power by reducing parasitic losses, but it'll prolong the life of belt driven accesories, especially your power steering pump. I think the engine itself will last for a reasonable amount of time but don't expect it to last as long as an engine that spends that same amount of time at 2000 rpm's.