I'm guessing because at highway temps the oil gets hot enough to deep clean the engine, so an engine with highway miles has seen a lot of power cleaning. Is this on the right track?
They say "highway miles" cars last longer because?
- Thread starter zerosoma
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Because cars are meant to be driven, not sit around. If they are well maintained I have no problem buying a HM car for cheaper.
We actually had a guest professor in my kinematics class last week who talked about this exact issue. He is specialized in fluids/lubrication and bearing design.
The oil pump basically just brings the oil to where it is needed. On the parts that rub, the lubricant creates a (hydrodynamic?) film that prevents contact and wear. At higher RPM, this fluid film is greater than at lower speeds. So in a nutshell, at elevated RPM's you get better lubrication. If you idle a lot the oil is not as effective in preventing wear.So a highway driven car should have less wear than a car that experiences stop/go or long-term idling.
Of course, it was much more detailed and advanced then that. I never took a bearing/lubrication class (yet), and hope to take him before I graduate. He is an amazing professor... So I am sorry if I maybe skewed some details for those who know better.
The oil pump basically just brings the oil to where it is needed. On the parts that rub, the lubricant creates a (hydrodynamic?) film that prevents contact and wear. At higher RPM, this fluid film is greater than at lower speeds. So in a nutshell, at elevated RPM's you get better lubrication. If you idle a lot the oil is not as effective in preventing wear.So a highway driven car should have less wear than a car that experiences stop/go or long-term idling.
Of course, it was much more detailed and advanced then that. I never took a bearing/lubrication class (yet), and hope to take him before I graduate. He is an amazing professor... So I am sorry if I maybe skewed some details for those who know better.
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- Transmission is shifting less, less wear.
- Engine is staying within an optimum RPM range, not accelerating from idle, then going back down to idle again. Less wear, fuel dilution and moisture get burned off.
- Brakes get used less.
- Highways MAY be smoother than surface streets, increasing life of suspension components.
- Cooling system is getting plenty of fresh air, not having to work very hard to keep things cool.
- Engine is staying within an optimum RPM range, not accelerating from idle, then going back down to idle again. Less wear, fuel dilution and moisture get burned off.
- Brakes get used less.
- Highways MAY be smoother than surface streets, increasing life of suspension components.
- Cooling system is getting plenty of fresh air, not having to work very hard to keep things cool.
It has nothing to do with a clean engine. I just bought a 2003 Focus with only 80k miles and it's spotless through the fill hole. However, the records show that an EGR valve needed to be changed. Why? Because during short trips the engine doesn't spend much time at operating temperature, so it produces more soot and other emissions. This will affect emission equipment and oil, so changing oil is critical in these types of scenarios.
Highway miles mean that the car spends most of its time at a steady speed, RPM and operating temperature. These parameters mean that the engine produces the least amount of contaminants and emission particles, which in turn doesn’t clog catalytic converters, EGR valves and leaves the oil cleaner.
In reality the engines will last probably the same with either driving cycles, provided proper maintenance was done, but it is the emissions equipment and suspension that will see the difference.
Highway miles mean that the car spends most of its time at a steady speed, RPM and operating temperature. These parameters mean that the engine produces the least amount of contaminants and emission particles, which in turn doesn’t clog catalytic converters, EGR valves and leaves the oil cleaner.
In reality the engines will last probably the same with either driving cycles, provided proper maintenance was done, but it is the emissions equipment and suspension that will see the difference.
A few things.
-Like xBa380 said, lubrication is better at cruising RPMs.
-Heat-cycling (short trips) isn't good.
-Combustion is dirtier at idle and when accelerating, especially when the engine is cold. (Fuel-air ratio is higher).
-Accelerating (stop and go traffic) puts more load on the engine.
-Even at higher speeds (say, 80mph), the horsepower requirement to maintain speed (absent large hills, of course) is fairly low, relative to the engine's peak output.
-Like xBa380 said, lubrication is better at cruising RPMs.
-Heat-cycling (short trips) isn't good.
-Combustion is dirtier at idle and when accelerating, especially when the engine is cold. (Fuel-air ratio is higher).
-Accelerating (stop and go traffic) puts more load on the engine.
-Even at higher speeds (say, 80mph), the horsepower requirement to maintain speed (absent large hills, of course) is fairly low, relative to the engine's peak output.
All these comments make sense. Two more: 1) if an engine will last for a finite number of revolutions, those revolutions will take the car much further on the highway than around town with idling, spending time in lower gears, etc., and 2) conventional wisdom is that a very large part of engine wear occurs on start-up of a cold engine, which highway travel naturally avoids.
One thing I didn't see mentioned so far is the fact that in addition to the other reasons above, for the same number of miles the highway biased vehicle will have actually turned fewer RPMs and have that many fewer hours of operation.
I think its regional. If a seller says everyday on the beltway then I'd not get that car either! Highway miles in mojave isnt the same as "highway miles" near/in cities that were built before cars such as east coast.
Ive actually poked around on craigslist and seen potential in vehicles that were owned by people from mountain communities. If the weather is super bad they will park a honda and drive a 4wd. The brakes and suspension are probably addressed more because it's sort of life and death coming down twisty roads, or accelerating a blind curve and discovering stopped vehicles in front of you.
Ive actually poked around on craigslist and seen potential in vehicles that were owned by people from mountain communities. If the weather is super bad they will park a honda and drive a 4wd. The brakes and suspension are probably addressed more because it's sort of life and death coming down twisty roads, or accelerating a blind curve and discovering stopped vehicles in front of you.
I was just wondering this the other day. I saw an ad for a Ford Freestar van listed as having 779,000 highway miles... Not sure if it was a typo or what but to me the fact that they are "highway miles" makes no difference.
The less moving parts have to change direction and speed the less they wear.
There was a book on how to make your car last nearly forever and the author went so far as to recomment parking on the street vs in the parking lot to save half a dozen steering maneuvers that would be needed to drive into the lot and enter a parking space vs parallel parking on the street. Forget about it. I'll just have the tie rods and ball joints replaced once in a great, great while. Not worth it. Besides can get side swiped on the street.
Since I live in SE Michigan where they pour road salt out all winter long, my vehicles are going to rot out before they wear out, so I say drive 'em hard and have some fun before it rots out.
There was a book on how to make your car last nearly forever and the author went so far as to recomment parking on the street vs in the parking lot to save half a dozen steering maneuvers that would be needed to drive into the lot and enter a parking space vs parallel parking on the street. Forget about it. I'll just have the tie rods and ball joints replaced once in a great, great while. Not worth it. Besides can get side swiped on the street.
Since I live in SE Michigan where they pour road salt out all winter long, my vehicles are going to rot out before they wear out, so I say drive 'em hard and have some fun before it rots out.
Just read the owner's manual. Stop and go driving is considered "severe service," and the mfg. often recommends changing the oil and filter twice as often under those conditions. Another factor, I believe, is that many vehicles' performance characteristics are optimized for highway operation, resulting in less wear. For example, at steady highway speeds many vehicles run a very high gear, resulting in lower rpms.
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Highway driving is good for an engine because the cylinders get hot enough to burn carbon deposits off and assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
The oil staying warm also gets rid of fuel contamination and helps clean the engine.
Obviously the reduction in stop starts and higher forces from changing speed helps as well, but in general terms a car driven mostly on the highway will last 2 to 3 times as long in engine main block terms than one that spends most of its time in the city.
The oil staying warm also gets rid of fuel contamination and helps clean the engine.
Obviously the reduction in stop starts and higher forces from changing speed helps as well, but in general terms a car driven mostly on the highway will last 2 to 3 times as long in engine main block terms than one that spends most of its time in the city.
Originally Posted By: skyship
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
I might add to the valuable acounts above, that in vigorous university studies (real time atomic count on irradiated parts) engine wear accours most during RPM+ delta (accel) and this is lessened in steady state operation.
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Originally Posted By: surfstar
Originally Posted By: skyship
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
I think he/she intended stoichiometric mode
Originally Posted By: skyship
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
I think he/she intended stoichiometric mode
Originally Posted By: skyship
Highway driving is good for an engine because the cylinders get hot enough to burn carbon deposits off and assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
The oil staying warm also gets rid of fuel contamination and helps clean the engine.
Obviously the reduction in stop starts and higher forces from changing speed helps as well, but in general terms a car driven mostly on the highway will last 2 to 3 times as long in engine main block terms than one that spends most of its time in the city.
'
In the US, cars don't have lean burn due to our poor quality gasoline. They may run lean-er, but they still are running
pretty rich.
Highway driving is good for an engine because the cylinders get hot enough to burn carbon deposits off and assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
The oil staying warm also gets rid of fuel contamination and helps clean the engine.
Obviously the reduction in stop starts and higher forces from changing speed helps as well, but in general terms a car driven mostly on the highway will last 2 to 3 times as long in engine main block terms than one that spends most of its time in the city.
'
In the US, cars don't have lean burn due to our poor quality gasoline. They may run lean-er, but they still are running
pretty rich.
Quote:
In the US, cars don't have lean burn due to our poor quality gasoline.
Is this true? I have read on BITOG before about this "poor quality," but is there any proof of it? Hard to believe our gasoline is of lower quality than other countries, though I realize most of our gas has ethanol in it now. What makes for "poor quality?"
In the US, cars don't have lean burn due to our poor quality gasoline.
Is this true? I have read on BITOG before about this "poor quality," but is there any proof of it? Hard to believe our gasoline is of lower quality than other countries, though I realize most of our gas has ethanol in it now. What makes for "poor quality?"
Lean burn mode is what many folks refer to the fuel control units setting which gives the leanest mixture. Most engines built within the last 10 years have electronic fuel injection control and that adjusts the mixture every time you step on the gas in addition to more normal temperature related changes. In general terms the more you stay in lean burn mode the better it is for the engine, for both diesel and petrol engines.
Might be called Stoichiometric mode in the US:
A stoichiometric amount or stoichiometric ratio of a reagent is the optimum amount or ratio where, assuming that the reaction proceeds to completion:
1.All of the reagent is consumed,
2.There is no shortfall of the reagent,
3.There is no excess of the reagent.
Might be called Stoichiometric mode in the US:
A stoichiometric amount or stoichiometric ratio of a reagent is the optimum amount or ratio where, assuming that the reaction proceeds to completion:
1.All of the reagent is consumed,
2.There is no shortfall of the reagent,
3.There is no excess of the reagent.
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Originally Posted By: surfstar
Originally Posted By: skyship
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
Take it easy.
Originally Posted By: skyship
assuming you don't change speed too often the engine stays in lean burn mode so they don't form in the first place.
Hmm, and which engine is this? Any 'ol engine has 'lean burn mode'? Really?
I think I'm joining others here that are getting tired of your spouting of incorrect 'facts' lately.
Take it easy.
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