[Rando]

I've read everywhere that short trips (like <10 miles) are tough on the engine, and the computer definitely decreases service intervals for that.

I'm trying to understand why. Here's what I don't get:

Say you drive 5 miles, then stop. You have put some wear-and-tear on the engine. But the guy who drives 50 miles also puts the same initial wear-and-tear on his engine!

My understanding is that oil has not fully circulated -- which means that the NEXT time you start the engine, you place more wear-and-tear if the previous trip was not long enough. Is that the right way to think of it?

The oil temp argument wouldn't apply, because the oil cools down between trips. (Assuming they are at least 6 hours apart or so.)

Thanks!

[Couch]

I would say that for one, your 5 mile trip, the car wouldn't have enough time to completely warm up. So I would think, theortically, oil temp would apply. As it takes ~15 minutes for it to warm up.

[UFOGUY]

the worst thing you can do with your car is to start it.

cold starts produce 95% of wear on your engine because engine components must operate without being fully lubricated. also, the oil doesn't lubricate as designed until it reaches a sufficiently high temperature.

once an engine is at operating temperature and crusing on the highway there is very little wear on the engine becuase it is fully lubricated at the proper temperature and the oil is also able to be better filtered since it is at proper temperature.

lots of short trips will produce vastly more wear on an engine than an equal amount of miles at proper temperature.

with seven quarts of full synthetic oil our cars are very well lubricated.

[Hotan Braskey]

One byproduct of combustion is water. Without fully allowing the engine to come up to temperature (by only taking short trips, for example), it does not get hot enough to fully dissipate the water in the system, so there is a chance for water to to become absorbed in various seals, gaskets, etc, and possibly making it into the oil. This decreases the lubricating powers of the oil, causing more engine wear. Or something like that

[335i4u2nv]

wow there's actually some great info on here

[Rando]

Thanks for the replies. I think I need to rephrase my question:

Is it any worse on the engine to:

Drive one 5 mile trip each morning, and 5 mile trip each evening

VERSUS

Drive one 20 mile trip each morning, and a 20 mile trip each evening.

And if one is worse, why?

Thanks!

[LACA335i]

Originally Posted by Rando

I've read everywhere that short trips (like <10 miles) are tough on the engine, and the computer definitely decreases service intervals for that.

I'm trying to understand why. Here's what I don't get:

Say you drive 5 miles, then stop. You have put some wear-and-tear on the engine. But the guy who drives 50 miles also puts the same initial wear-and-tear on his engine!

My understanding is that oil has not fully circulated -- which means that the NEXT time you start the engine, you place more wear-and-tear if the previous trip was not long enough. Is that the right way to think of it?

The oil temp argument wouldn't apply, because the oil cools down between trips. (Assuming they are at least 6 hours apart or so.)

Thanks!

a short trip will wear your engine fast and rob your gas really fast. It is called stop and go. it also wear your brake easy and fast. Your bmw engine love long distance drive cause it always be at cruise. Engine love Cruise because it does not need to work too hard on the combustion chamber.

[Nikolas]

Originally Posted by Hotan Braskey

One byproduct of combustion is water. Without fully allowing the engine to come up to temperature (by only taking short trips, for example), it does not get hot enough to fully dissipate the water in the system, so there is a chance for water to to become absorbed in various seals, gaskets, etc, and possibly making it into the oil. This decreases the lubricating powers of the oil, causing more engine wear. Or something like that

Absolutely correct. We are all so concerned with the oil temps, but those temps must be high enough to remove water from the system. Well at least 212F

[UFOGUY]

a longer trip is always better since the oil will be sure to reach operating temperature and can therefore be better filtered and relieved of moisture, etc. assuming the 20 mile commute is NOT stop and go traffic.

a periodic highway cruise is the best thing you can do to filter your oil.

i wouldn't worry much on this topic. remember, you are running SEVEN quarts of pure synthetic long life oil. your car benefits from the best protection available at this time (with the exception of installing an AMSOIL dual bypass filtration system).

check out this site for more info on oil. there is much to learn and i only know enough to be dangerous.

http://www.bobistheoilguy.com/

[BMWI6]

Originally Posted by Rando

Thanks for the replies. I think I need to rephrase my question:

Is it any worse on the engine to:

Drive one 5 mile trip each morning, and 5 mile trip each evening

VERSUS

Drive one 20 mile trip each morning, and a 20 mile trip each evening.

And if one is worse, why?

Thanks!

the 20 mile trip will be worse under the same road conditions because you are putting the same initial wear, plus the added wear of the additional miles which is not too much after the engine is warmed up. now two 5 mile trips in the morning and two in the afternoon could add up to more wear than one 20 mile trip on each occasion. hope that helps

[pony_trekker]

Originally Posted by Rando

I've read everywhere that short trips (like <10 miles) are tough on the engine, and the computer definitely decreases service intervals for that.

I'm trying to understand why. Here's what I don't get:

Say you drive 5 miles, then stop. You have put some wear-and-tear on the engine. But the guy who drives 50 miles also puts the same initial wear-and-tear on his engine!

Because in 5000 miles you will have made 1000 starts while the other guy will have made only 100.

[pony_trekker]

Originally Posted by Rando

Thanks for the replies. I think I need to rephrase my question:

Is it any worse on the engine to:

Drive one 5 mile trip each morning, and 5 mile trip each evening

VERSUS

Drive one 20 mile trip each morning, and a 20 mile trip each evening.

And if one is worse, why?

Thanks!

Oh they're both the same. I thought you meant 4 5 mile trips versus 1 20.

[UFOGUY]

what are the driving conditions on these two scenarios? all stop and go, highway, what?

if you are NOT making exclusively short trips all the time then i wouldn't be the least concerned about wear. your oil will be cleaned and purged of moisture during highway driving. and i hope you are getting some highway miles on your car because that is where your bimmer will shine.

if you are concerned about the condition of your oil i highly recommend that you have it analyzed after your next oil change (blackstone labs does this) and it will show what type of wear is occuring in your machine. i have done this in the past on a diesel and the analysis is really informative

bottom line, as noted above, the MORE cold starts you make the more wear and tear on your engine.


trust me, we probably have the best engine oil systems available.

[anerbe]

most people are correct here with the conditioning of the oil and removal of water from the engine.

there is also an issue of incomplete combustion and carbon build-up in the engine.

someone only going 5 miles may not fully warm up the engine, thus resulting in lower revs. There may be areas in the engine that get oil, but may not get warm enough to be replaced by circulating oil (causing a sludge build-up).

although this could be remedied by occasional high throttle applications, this is less probable in a 5 mile commute than a 20. make sure you put the car through its paces once in a while.

[demosthenes]

Originally Posted by anerbe

most people are correct here with the conditioning of the oil and removal of water from the engine.

there is also an issue of incomplete combustion and carbon build-up in the engine.

someone only going 5 miles may not fully warm up the engine, thus resulting in lower revs. There may be areas in the engine that get oil, but may not get warm enough to be replaced by circulating oil (causing a sludge build-up).

although this could be remedied by occasional high throttle applications, this is less probable in a 5 mile commute than a 20. make sure you put the car through its paces once in a while.

Agreed.

So the answer to the OP's question is that the 5 mile trips are harder on the engine IF that's all you drive. Plus, the colder the outside temperature and the more traffic you encounter, the harder it is. Plus, as the previous poster stated, we shouldn't be revving our engines until they are warmed up, so the 5 mile trips are done with the engine at lower RPMs, further contributing to the problem.

[Chowbow]

The worst "times" for a gasoline engine is 1) warm up, and 2) idling. Take 2 cars with 10k miles on each of them. One car makes a single 100 mile trip everyday, and the other makes 20x 5 mile trips the same day. Each time the car is started, the engine will have to warm up to temp. Out of the two cars, the one that does the short trips has to warm up 20x as much everyday. Granted it may not be fully cooled down each time but the point remains that the engine does have to start again and warm up again.

The same thing goes with stop and go traffic versus constant driving... There is less wear and tear on the engine when there is a load on the engine while the car is in gear, versus the engine idling along in traffic.

I wouldn't say the more oil our cars hold, the better the oil system. I mean you could take a tiny 4 cylinder Mazda pickup that holds 4 quarts of oil, and put a bigger oil pan in there so that it holds 15 quarts of oil... The actual oil pump will be the exact same thing. Quantity of oil in the system doesn't necessarily mean a good system, although I agree that typically, BMWs do have above average oil circulation systems.

[maximka]

+1

[Rando]

Great answers and information, thank you all.

pony_trekker actually answered why the oil change interval thing needs to tick down after for the guy who makes short trips -- it probably deducts quite a few miles "per start". Obvious perhaps, but I hadn't really thought about it that way.

[F32Fleet]

Don't forget rusting of exhaust system due to excessive water build-up, and fuel/water build up in crank case since oil isn't heated enough to burn off.

[KaiserCO]

Originally Posted by Rando

Thanks for the replies. I think I need to rephrase my question:

Is it any worse on the engine to:

Drive one 5 mile trip each morning, and 5 mile trip each evening

VERSUS

Drive one 20 mile trip each morning, and a 20 mile trip each evening.

And if one is worse, why?

Thanks!

the way i understand it...which could be wrong... it's better to drive one twenty minute trip than to drive 4 trips of 5 minutes

[nyc3r]

yea yea but who cares, you got the car to drive it.. don't stay home just because you don't want to 'start' the car.. drive it!

[Kiemyster]

Originally Posted by nyc3r

yea yea but who cares, you got the car to drive it.. don't stay home just because you don't want to 'start' the car.. drive it!

+1