Don't confuse the issue guys -- this thread wasn't about personal preference regarding gear choice -- it was about whether running at a little higher rpm was bad for the car. That's simply one piece of the data one needs to make an informed gear choice. (And as I recall, the original poster had already made his gear choice)
Most of you are too young to remember what it used to be like. Overdrive tranny's and really low cruising engine revs are largely a product of the EPA. As CAFE requirements got tighter, manufacturers achieved their highway mileage numbers largely with long rear gears. The fox bodies are a classic example -- a 2.73 gear with a .675:1 overdriven 5th. Not to save wear and tear on the engine - but to achieve a certain highway mileage number. Drop on back to the 60's when all the domestic cars were running 3 speed automatics (the vast majority) or 4 speeds -- top gear was 1:1. And a pretty standard rearend ratio was 3.00:1 or 3.23:1. The tires were a bit taller - but not much. (to compare that rear gear number to the Fox number - multiply 2.73X.675) The engines routinely saw MUCH higher revs under cruise. And they were aerodynamic slugs that weighed more which made the engine work harder to push them through the air at a given speed. And even with poorer oil, poorer machining and assembly, carbs/points (tuneups pretty much required every 6000 miles just to keep them from missing) -- cars routinely lasted 100K. Our 65 Olds Vista Cruiser had 156K miles on it when Dad sold it - still in very good working order. Many, many of those miles were put on loaded with 5 kids and luggage and spinning along at about 3000 rpm at 70-75 mph on the highway. And we weren't the only ones -- millions of other high mileage cars out there under similar conditions during that time period.
Let's add another one in -- most of the smaller engined cars out there today are turning significantly more revs at cruise than the stock 5.0's. Even though some are lighter, most need the torque multiplication that comes with more gear to make performance targets. So most of those 4 and 6 cyl. powered vehicles are zipping along at revs more like what we're seeing with 3.73 gears. And the majority of them are capable of about the same revs as the 5.0L -- they're good for about 6000 rpm -- it's not like we have 9000 rpm engines turning at 3000 rpm. Do you have any idea how many 100K+ mile Civic/Accord/Camry/Corollas there are out there still running just fine?
The point isn't whether there's more wear/tear -- the point is whether the additional amount is SIGNIFICANT -- remember the post -- between 70-80 mph. It's not significant. You do A LOT MORE to shorten the life of the motor/car/driveline every time you take it to the track, or run it hard through the gears, or play burn-out king, than you will cruising it at 500 rpm higher. So if less wear /tear is what you're after - there are a lot of more impactful driving behaviors that should be focused on than simply cruising with 500 more rpm. And for those of you that seem really paranoid about it (5 spd) -- perhaps you should just idle it around. That way there's no more wear and tear than absolutely possible.
As for the youngster spending his hard earned pay from MickeyD's on his ride, I couldn't agree more Couped -- the best thing we can do is coach him to mod the car correctly -- including fixing any vibrations that come along with his mods and understanding the implications of his choices. But he'd get his biggest bang for the buck (in terms of longevity) laying off the Friday night burnouts and attempted ricer kills.
Should they worry about driveline integrity from spinning the shaft faster? Yes - they should pay attention to that. Should they worry about hurting a good running, well maintained engine by spinning it 500 rpm higher on the highway? No - they don't have to worry about that.
Lastly - on the 100K mile rebuild front - if you've got a well maintained engine with a few accurate gauges, there's no need for pre-emptory rebuilds. Your oil pressure gauge and a periodic examination of your used oil filter will tell you if you've got a bearing issue rearing it's head. You should be cutting a filter open every 4th or 5th change -- cut them all open if you like. It's easy to do. With a little common sense, you can run very high miles without any needless worry about blowing it up unexpectedly.