Yeah, some folks will say, shift at lower rpm as long as the engine is not lugging; and they'll add that lower rpm means lower piston (etc.) speeds and this equates to less friction (which increases with the square of the velocity) and therefore less engine wear.

That's all fine, but there's the other side of the coin. I'm not an engineer, but referring to an article (one of the several car mags I've read for the past 45 years) several (or many -- at my age there's little difference) years past, it recommended moderate to high rpms often (like everytime you shift). It seems that if you don't get the piston rings and/or cylinder walls nice and hot, "varnish" (the article's words) forms on the surfaces -- this substance tends to repel oil (it doesn't have the adhesion that metal has), and so oil won't stay on the surface. This, in turn, will lead to greater cylinder-wall or piston ring wear. Moral: you're encouraged to use higher (although not excessive) rpms for greater cylinder longevity.

And here's another tale. A decade or more ago, I had a nice conversation with my Mercedes (when I had a few cars of that make, along with my Volvos) dealership's service manager on his lunch break -- we were just sitting and talking about everything. But the conversation went to making the engines last. He told me that the biggest mistake owners make is in babying the engines, and he explained that you have to get the pistons nice and hot to get them to expand to their full "hot" dimensions once in a while to wear down the "lands" of unworn cylinder on the top and bottom of the bores -- if you don't, they'll build up (or rather, won't wear down) and then, when you really need the engine's full power, you have the pistons smashing into the ridges, causing all sorts of stresses on the pistons and cylinders.

And, personally, I use high rpms a lot! But I also use a good (AmsOil) synthetic with phenomenal film strength to negate much of the high speed friction shortcomings of driving like this. In fact, my daughter once had a boyfriend (who was taught by his father) who let her use his car once in a while, but he instructed her to always shift early. Then I once rode with her, and she emulated her boyfriend -- I told her flat out that while he wants her to drive his car like that, she should never, ever drive any of my cars like that! But that's me. Anyway, my engines last (without using oil) 250 to 350K miles, so I must be doing something right.

So, now you're confused. Welcome to the club -- go with your gut!

Regards,

"Cleaner" is a relative term. Most of the gas you buy today allready has some sort of additive to help keep valves clean. No need to do any "Italian tunups". As long as your engine isn't lugging you shouldn't have any problems. It's hard to say what's best to do all the time but after all that's part of the fun of driving a stick. You can vary your driving style and pretty much drive it like you want and not be locked into the way the automatic's computer is programmed. One on the many little things we all can do to help keep our minds busy and keep the Alzheimers demon away.

Your overall efficiency is usually best if you shift near the max of the torque curve for your engine which is probably near 2000-2500 rpm. That's where an automatic is usually programmed to shift during moderate driving. And it's why experienced bicyclists use their gears freely to help maintain the cadence they are most comfortable with. The issue is not critical unless you are revving so low that you lug or lose power or so high as to risk premature wear or mechanical damage. When driving a manual I try for smooth acceleration at the rate needed - that is likely to be more or less the most efficient.

No reason to believe shifting habits would affect engine condition. Your engine's control system automatically compensates for a wide range of gasoline octane variations.

If you are driving under heavy loads or doing extremely severe work with the car I would be more concerned about the clutch and driveshafts than the engine, unless you are overheating.