avoiding cold starts

Modern engines with modern oils are way less sensible to cold starts. What you are doing does not do any noticeable good for your engine, and technically does not hurt either. It hurts your wallet and our ecology, though.

Define cold. Cold to me is anything below 85F. Below 50F and I don't go outside.

I would dispute that it puts "a lot" more stress on it. Cold starts with modern oils of the correct grade for the climate you're in are really a non-issue. Yeah, a modern engine may piston-slap like a diesel when its cold and sound very different than when its hot (unlike older engines with different piston alloys and designs that traded efficiency for quiet when cold,) but that's a completely harmless sound. It would be far more harmful if the pistons bound in the bore when the engine was fully heated up.

You're probably doing HARM through excessive fuel dilution into the lubricating oil.

Interesting....I was reading in the past few years that idling doesn't hurt the engine any more than driving does....but i think a LONG time ago I used to hear that it's not good to idle too "long" (an hour?).

One slightly related (to my original question) thing I heard last year: If your going to let you car sit parked (off) for a long time (weeks??), you should NOT 't drive a short distance and then turn the engine off before the long parking duration....You should drive it until it's fully warmed up....supposedly the condensation in the engine would remain there and cause rust if you don't fully warm it before turning it off and letting it sit.......true?

Must have been when carburetors were the norm. I can't imagine that a modern fuel-injected and electronically controlled engine would have problems with idling for long periods of time.

Modern motor oil is probably better in handling all this stuff. Many (if not most) engines these days are aluminum. I've never had an oil analysis with any appreciable amount of moisture, even when taken after a short drive.

Depending on where you are leaving the engine idling may be illegal. It is also a very poor idea since many of the insurance companies have it buried in the fine print that leaving the keys in the vehicle means they don't have to cover it in the event of loss/theft. It is also not required with modern vehicles and oils.

Your Owner's Manual will probably say you are in the severe driving condition catagory. As far as oil change intervals, it means follow the RECOMMENDED o.c.i. If I were in this situation, and using my favorite synthetic engine lubricant, I have the option and confidence to follow what it claims on the lable.

The problem isn't idling, its idling when cold. Idling will *never* bring the oil up to full operating temp, even if the coolant gets there, and its the oil that really needs to be heated to drive out absorbed fuel and water vapors.

Its not that it causes rust, its that it causes acid formation in the oil. But yes, its generally true. An occasional short cold trip really isn't going to do any harm because the buffers in oils can handle the acids just fine. But doing that sort of thing on a daily basis will eventually overwhelm the oil and the total base number will decline, meaning the oil is becoming acidic.

On the Canadian Prairies:

85F = Hot day. Stay in the shade. 50F = Might want a sweater on. 40F = Time for the jacket. 20F = Time to change the oil. Max 5W30, maybe 0W30. 0F = Getting a little chilly. Might want to warm the engine for two or three minutes before driving or it might cough and die.

-20F = Plug in the block heater. Put on long underwear. Wear a hat.

-40F = Some parents keep kids at home from school. The rest of us go to work.

-50F = Can't talk outside. Your words freeze and fall to the ground, and in the spring everyone can hear what you said about them when those words melt.

-60F = Smoke freezes in the chimney and the furnace fumes back up into the house. Got to climb up on the roof and poke a long stick down through the frozen smoke, turn the heat way up and burn the rest of it out.

-70F = Can't drive at night. The headlight beams freeze to anything they hit and immobilize the vehicle. Have to turn off the lights to get moving again.

Dan