A friend of mine who is very anal retentive, has to move his car twice a week to the other side of the street. But instaead of just moving the car, he insists on taking it for a five mile ride first because “short trips are bad for the car”. I am aware that short trips will not allow moisture in the exhaust pipes to evaporate, causing them to rust away quicker, but are short trips really bad for the engine?
Yes, they are. In a short trip The engine may not get up to full operating temperature. Oil changes every three months are a definite must.
You’re not telling me why they’re bad Sky.
Besides the rust potential, the oil tends to gum up when it doesn’t reach full operating temperature.
With a short trip, the engine might not reach normal operating tempurature, imparing oil flow.
"Short-trip driving is especially hard on oil because the engine never warms up enough to boil off the moisture that accumulates inside the crankcase. The moisture comes from combustion gases that blow by the piston rings. Most of these gases are removed by the vehicle’s PCV system. But in a cold engine, much of the moisture condenses and ends up in the oil.
“Water reacts with oil to form sludge and acids, and the result is accelerated engine wear.”
Apart from the temperature issue, the oil is simply all sitting at the bottom in the sump, so for a few moments, there is minimal lubrication.
Now, I am not a mechanic, but x-ray I suspect your friend doen’t know what he’s talking about.
Start-up is bad for the car, yes. whether your friend U-turns to the other side of the road, or takes it for a run of a few miles, he’s still started it up one more time regardless. As driving a cold car isn’t good for the engine, I think he’s better off just driving the thing across to the other side of the street and be done with it.
The “short trips” thing refers to the number of start-ups made over a given mileage, not the number of start-ups generally. Thjis is why you’ll see taxis plugging away on the original engine with half a million miles on the odometer, because the cabs are often running 24/7. One driver gets out, the other gets in. The same model car driven twice a day to work or to the mall, however, will probably get motor trouble at 200 000 miles.
Short trips are bad on a number of levels
First off for every gallon of gas you burn a gallon of water is created. If the engine does not get to full operating temp the water will not boil off from the oil (some of it will slip past the rings into the crankcase) Water is not a wonderful lubricant.
Secondly if the engine does not get to full operating temp, the exhaust for sure does not get hot enough to dry out either leading to the exhaust rusting out before its time.
Next comes the fuel mixture cold. Extra gas has to be added to make the engine start and run cold. This extra gas tends to wash the film of oil off the cylinder walls. If the engine is only driven cold (across the street and back as in the OP) the life of the engine would be shortened.
Also some of the rich mixture will also slip past the rings into the crankcase so that the oil will also get diluted with gas. Gas is also not a great lubricant. The rich mixtures will also tend to increase the chance of a fouled plug.
With all that said, do I drive 10 miles every time I start my car? Hell no, but most of the time I drive plenty far enough to get the oil fully warm and everything happy.
For what its worth, modern catalytic converters require at least five minutes of driving to heat up to operating temperature. The first few minutes of your journey your vehicle is essentially operating without a cat; of course, those five minutes still exist even if you keep driving after the thing warms up, and this has no bearing on engine or drivetrain wear. It just means lots of short trips are worse in a polluting sense than one big one.
I think what most people are saying is that over 5000 miles, short trips are worse than long trips whereas what x-ray vision is really asking is if over 5000 trips, short trips are worse than long ones.
What I’m suggesting is that 5000 ten minute trips are worse for the car than 5000 ten second ones. The engine wear five minutes after starting is less severe than immediately at start-up, but you’re getting the start-up wear regardless. Why add to it?
I find TheLoadedDog’s argument quite persuasive.
The dude probably does occasionally actually drive the car somewhere, which will get the engine hot enough to boil off any accumulated water in the oil.
If, OTOH, he only ever moves the car across the street, you might ask him why he’s got the friggin’ thing in the first place.
I’m with TLD all the way.
This is an Aussie conspiracy.
What counts as a short trip?
There are, obviously, two separate questions and two answers. From reading the posts, it seems that short trips are worse for the exhaust system than long ones, since it doesn’t dry out. For the rest of the system, it seems likely that if you occasionally take a long trip to boil oil off the water, then the fewer trips you take the better, but short trips are no worse than long ones.
I drive maybe twice a week. One day a week, I go two miles to the supermarket and back and on average once a week I go four miles downtown and back. And two or three times a year, I go 500 miles and back. My owner’s manual says that the car must be driven daily for good performance, but after 13 1/2 years and 98 million meters, it is still going fine.
I think the issue is, how long does your friend want to keep the car for?
Engines are rarely the first things to fail on a car. You’re much more likely to have to spend a bundle on other parts before the engine fail.
If your friend is going his regular oil changes (based on time, not miles) his engine should be fine (although, I wouldn’t want to buy his car). I can’t say the same for several other parts that might stop working if left out for too long.
My sister once left her Grand AM out for a winter. After it was boosted it worked, but her brakes had seized because of rust.