I certainly have a lack of knowledge in this area, so I thought I'd
throw it out there.

I have a 2004 Audi A4 1.8T - which is an automatic, but with
'triptronic.' Here, I can essentially change gears with the flick of
my wrist. I was wondering, however, if keeping it in 3rd gear (around
70 mph and 5000 rpm) for an extended amount of time (30-40 minutes) is
damaging to the engine? I know that it burns a fair amount of fuel (to
say the least), and I make sure the engine doesn't get too hot - but
the allure of that 'sporty pickup,' especially on the highway, is
awesome.

Thanks.

http://dmoz.org/Shopping/Vehicles/Parts_and_Accessories/Performance/

http://dmoz.org/Home/Consumer_Information/Automobiles/Purchasing/By_Make/Audi/New/

Hi telarium-ga,

   I do not see any problem in continually running the engine at a lower
gear, as long as you do not see the engine getting overheated(ie. the
radiator is functioning fine, and the thermostat controlled overheat fans
are running).  The only downside is an increased fuel consumption. You
might also need to change the engine oil and the transmission fluid at
a reduced duration than the normally suggested interval, and also keep
your air filters and oil/fuel filters in top condition(A clogged/underperforming
air filter could lead to excess of unburned fuel and might lead to gumming
on the cylinder heads/valves, An oil filter keeps the oil clean to reduce
the quantity of suspended particles that could cause more damage at higher
engine speeds). This will ensure, that the engine life is not affected in
the long run.  Also since most of the damage to the engine occurs during
the cold start, it would be better, if you do not drive in lower gears(or
accelerate fast in the lower gear), till the engine warms up to normal
operating temperature. Avoiding use of A/C at low speeds(less than 30mph)
could help ease on the overheating possibility. You could also try high
performance coolants for the radiator(which may not help with avoiding
freezing), or other additives to reduce surface tension for improved cooling
performance.

Hope you find this information helpful.

Regards
ldavinci-ga

Thanks, daytrader and ldavinci. 

Yea, I'm always careful to not work the engine too hard on a cold
start, and I always let the engine cool down before I turn the car off
when I'm running at high revs for a long period of time.

I believe the AC automatically shuts off when running the engine hard
at low speeds, anyway - and will shutoff if the engine gets too hot.

Thanks,

Brad

I've owned a number of high performance cars from 300ZX twin turbo to
Vipers. Plus I've built a few race cars.

I would never suggest to anyone to run any car engine at 5000 rpm for
40 to 50 minutes.  The reason for this is: Car engines are made to run
"most of the time" at about 1000 to 1500 rpm.  You are just increasing
the wear and tear on the engine.  Race engines run 5000 to 6000 rpm
for one race and then are taken apart and rebuilt.  The reason for
this is the wear.  If you continue to run that engine that hard you
are asking for trouble and decreasing the life of the engine.

If you do decide to keep running the engine at these high rpm, then I
would suggest changing your oil every 1000 miles, add a big trans
cooler, add a oil cooler.


I hope this helps.

I agree with just4fun2-ga. Think about it, you are making a hunk of
metal move repeatedly in a high pressure and temperature environment
5000 times a minute rather than 2000-3000 (about what I rev at doing
70 on 5th gear on my '99 A4) a minute. Increased wear and tear.
Granted Audi put an exceptional block in there, but cut it som slack.

Plus, you are never perpetually accelerating. Switch to high gear when
you are cruising, and learn to just down shift when you want to over
take / race.

I hope youre using synthetic oil too...

Hope this helps!