How do I know when I'm lugging my engine and doing damage? Yesterday on a slight uphill where the speed limit is 25 mph, I was able to maintain 25 in 5th gear at 1100 rpm. I was barely giving any throttle, just the bare minimum needed to keep the speedo at 25. This gave me instantanious mpg readouts of 58 mpg plus on my scanguage. There wasn't the normal rumble that you hear from the engine when lugging. So, even though I don't get the usual audible indications of lugging, am I doing damage to my engine at such a low RPM?
This is purely a opinion, but if your light on the throttle and it's not bucking and kicking, I think your fine. I think it becomes more of an issue as you try to open the throttle, under load. If your being conscious, careful and go easy, you should be fine.
driving around in high gears at low speed is just fine and a great way of using minimal power to sustain motion. when it comes to acceleration however i feel it's better to downshift one or two gears. don't be affraight to use the engines optimal power for a few moments when you actually need it.
trying to pull up in a to high gear will force your engine to deliver power below it's optimal peek wich is actually bad for FE. i used to try to always stay in an as low gear as possible, but recently i've started pulling up much more dynamically by downshifing sooner and upshifting a little later yet imediately going to my top gear again once i've reached the desired speed. my FE continues to improve so i believe it's the right thing to do.
As long as the engine running faster than idle and is capable of producing more power than you are presently requesting via your right foot, you are not lugging. If the engine produces (wide open throttle) 12 hp at 1000 rpm , and the road conditions are such that you need but 1/4 throttle to maintain speed, then you are not lugging.
also this is in a truck, correct? the engine is tuned for decent low end power.
with my VX if I try to push the engine slower then about 1,100 rpm on anything but perfectly flat, or even down hill grade, it starts to show signs of lugging, and I know it's hard on the drive train, I've already replaced the tranny once due to a worn main bearing and was warned about that being a commen problem.