Possibly stupid question...
I'm used to driving my car at about 1800 rpm's in 5th when cruising.
Just wondering if there is any danger to engine / transmission etc if I cruise (ie, maintain same speed on moderately flat ground) at 1500 rpm's in sixth gear. The engine sounds like it struggles more? Any opinions? thx

 

it is perfectly fine

 

i guess its fine but i'd probably just leave it in fifth, or even fourth for extra power on demand. It doesn't really matter if the engine is spinning more especially if the car is doing little-no work to keep it's speed which is probably the case as you are cruising on level/smooth roads...

 

I think it is fine as well, but for some reason ever since I installed my crank pulley I dont drive under 2000rpm's. Dont want to lug the motor around at such low rpm's especiallyt up a hill-I know I dont have to do this, but like I said for some reason now I do....btw 30+K miles on pulley with no issues.

 

You are fine as long as you don't try to accelerate quickly. Make sure you down shift.

 

Saves gas......

 

If the car sounds like its struggling, it is. I haven't tried it but 1500 RPMs sounds like it is to low for 6th.

 

Interesting observation - I have a "dip" before entering my drive to the carport. The drive to the carport is on a more that slight incline - If I dont practically stop the car will " bottom out" on the dip. To avoid this I slow down, put it in 1st before entering the dip - let out the clutch - and it will pull itself up the inclide by self feeding the proper amount of gas. It doesnt lug at all. Have noticed that on the level it will self feed gas in 2nd gear without lugging. This is great upon entering the carport as I want to avoid the bottoming out and not too fast into the port. Driving the 350 Z stick is a new experience from former stick cars I have owned over the years.

 

It's fine...Like someone said earlier, down shift before giving it WOT. Cruising is fine though at that RPM

 

And to add…I see a minor problem cruising at 1,500 RPM. If you want to get out of a dangerous situation by accelerating, you may have a problem.

 

Gasoline engines are built to rev. This is not a diesel!

Have a look at your oil pressure gauge when the engine runs below 2000rpm. Now tell me driving with 60% of max oil presure is good for lubrication!

 

It won't hurt it if you don't accelerate quickly.

 

If you're breaking in your car, this might be a high engine load.

 

required oil pressure has a direct relationship with rpms...the lower the rpms you are at, the lower your pressure requirements are.

 

It's still lugging your engine. Granted I don't know exactly how the rings behave at that speed. Fact is, I have plenty of my friends who drives their cars at low rpm. The blew their engines (head gasket, more often main bearings give up). Probably not related...

I rev my engine high, still below red line. I'm over 75k miles on the Impreza, with lots of lapping, gravel and ice rallies. No abnormal vibrations.

 

I think Kolia has a pretty good point. Low oil pressure = low lube. You should really only be down that low in rpms if you are coasting in gear. The heat from the explosions probably makes the motor too hot for such low oil pressure/low lube. Thermal breakdown, man. That's why motors are more efficient at the 2000 rpm mark. Little fuel, good enough lube.

 

can someone explain why it would be bad to go WOT in 6th gear at a low rpm? just curiousity.

 

Thanks guys for all your opinions. I wasn't exactly sure what happened with the engine at low rpm's. Obviously I do downshift to accelerate :P it's just that in 6th gear I save a lot of gas, i just want to be sure that the money i save on gas isn't offset by damage to the engine.

 

Cylinder pressure will rise pretty high for a relatively long period of time (slow rpm). The engine won't have enough lubrication on the cyclinder wall and main bearings, the oil film on wich everything is running can then fail and you now have metal to metal contact in your engine. Not good.

 

1500rpm and you're worried its struggling? This is no joke but I drop mine to 6th and do 28-30mph at about 1,000 rpm. Has very slight throttle but can definately keep it constant or even speed up slowly from there. 1st 2nd normal rpm, drop way down then 6th and cruise very quietly. Neighborhood, park, ect..