The thing to remember is that your oil pump and your coolant pump are crankspeed dependent.
Drive at too low an RPM and you're not providing adequate cooling or lubrication. And, the oil functions as both coolant and lubricant. It provides 60% of your engine cooling, and from some of the most critical areas. As it lubricates the main and rod bearings, it also carries away heat. Same with other areas of the engine, such as cam journals, where the coolant doesn't flow.
2200-2500 RPM is fine if cruising (though I prefer staying at 2500 or above).
But, there is a difference between cruising and accelerating. The engine isn't lugging if power output exceeds demand (such as cruising). But, I wouldn't mash the wow pedal from 2500 RPM in 5th to accelerate, this is where you want to select a lower gear first.
There's an old addage which is good advice: "when in doubt, downshift".
Cheers!
Last edited by Lil bastard; 03-22-2011 at 10:08 PM.
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