How often should you change your oil?

[Aaron 2NR]

That’s correct it’s difficult to get a mineral base oil below a 5w30 (molecular unstable)... that’s why most of the lower viscosity are full synthetics

[adnj]

Everything that you need to know regarding oil change is in the owner's manual. If you choose to change at a different interval or use a different engine oil spec, it is your perogative.

This. Everyone thinks they know better than the manufacturer.

Yeah, but the manufacturer recommendation is based on conventional oil.... synthetic is a whole different story

Many manufacturers, in various engine families, specify the use synthetic engine oil only. It is not unheard of for some OEMs to also specify a specific brand of oil.

When new drive trains are being developed, lubricant manufacturers are brought on board to provide a set of specific lubricant qualities. These form the basis of new lubricant specifications.

In my experience, many issues associated with engine oil is attributal to owners that refuse to service the air filter at the recommended interval.

[kamakazi]

Everything that you need to know regarding oil change is in the owner's manual. If you choose to change at a different interval or use a different engine oil spec, it is your perogative.

This. Everyone thinks they know better than the manufacturer.

Yeah, but the manufacturer recommendation is based on conventional oil.... synthetic is a whole different story

Many manufacturers, in various engine families, specify the use synthetic engine oil only. It is not unheard of for some OEMs to also specify a specific brand of oil.

When new drive trains are being developed, lubricant manufacturers are brought on board to provide a set of specific lubricant qualities. These form the basis of new lubricant specifications.

In my experience, many issues associated with engine oil is attributal to owners that refuse to service the air filter at the recommended interval.

Air filter?... Care to elaborate on that

[Aaron 2NR]

Poor air filtration allow elements into the system which can then be found in the oils which promote wear metals

[kamakazi]

How does refusing to change an air filter allow more dirt in?; Are you saying that the filter collapses and or fails?

[adnj]

Aaron nailed it.

A dirty air filter can lead to a rich fuel mixture, promote plug fouling and sooting. Black tail pipe emissions is caused by a rich mixture in either a gasoline or diesel engine. Though you don't need to see black smoke to have a rich mixture.

These deposits can and usually do become trapped in the engine oil. Oftentimes, these deposits cannot be filtered from the oil and decrease the lubricity of the oil.

Poor air filtration allow elements into the system which can then be found in the oils which promote wear metals

How does refusing to change an air filter allow more dirt in?; Are you saying that the filter collapses and or fails?

[Aaron 2NR]

How does refusing to change an air filter allow more dirt in?; Are you saying that the filter collapses and or fails?

Severely dirty air filter can allow contaminants to enter the engine. This is because the engine has to work harder to pull in enough air, the result is a vacuum effect that pulls in dirt and debris into the engine

[kamakazi]

so to answer adnj.
Yes that is a possibility but only in older vehicles that don't have any real emissions control systems. Modern engines will detect the lower volumes of air (if the filter is dirty) and subsequently pump less fuel to match; which negates a lot of soot formation (because emissions).

@Aaron 2nr.
I can only see a very dirty air filter allowing more contaminants (dirt/debris) into an engine if the filter media ruptures or fails due to excessive vacuum.

I honestly don't give much thought to air filters anymore, not that it isn't important, but because I leave them in pretty long (like 30000kms-40000kms; and the manual for my vehicle actually has 30000kms) and they don't seem to get to what I consider severe, in terms of appearance.

[adnj]

so to answer adnj.
Yes that is a possibility but only in older vehicles that don't have any real emissions control systems. Modern engines will detect the lower volumes of air (if the filter is dirty) and subsequently pump less fuel to match; which negates a lot of soot formation (because emissions).

One may wish to hope but that is simply not the case. Rich/lean fuel mix is a performance and emissions problem that gets plenty of attention from every OEM except Tesla.

Long periods at idle, high humidity, high temperature, hard acceleration, stop-and-go traffic, hill climbing, and heavy loads are the very conditions that make it tough to properly mix the air:fuel ratio.

A dirty air filter just makes the task more difficult.

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Engine Running Rich Causes

The ideal ratio of air-fuel mixture mostly depends on the amount of fuel in the combustion chamber. A number of components including oxygen sensor, ECM, and catalytic converter are vital to this process. So, any defect in them will cause the car to run rich or lean.

Possible causes of a car running rich:

Defect in the oxygen sensor

Faulty ECU

Defective mass airflow sensor

Dirty/clogged air filter

Blocked open injectors

Damaged engine coolant temperature sensor

Retrofitted cooling system


https://carfromjapan.com/article/car-maintenance/car-running-rich-things-you-should-know/

[kamakazi]

"Counterintuitively, dirty air filters don’t affect fuel economy or emissions on computer-controlled gasoline and diesel engines, as long as they were built after the introduction of closed-loop oxygen sensor feedback systems. Modern computer-controlled engines can adjust fuel injection to compensate for a dirty air filter, but carbureted engines depend on air flow for fuel delivery."

http://knowhow.napaonline.com/what-could-a-dirty-air-filter-do-to-your-engine/

[adnj]

"Counterintuitively, dirty air filters don’t affect fuel economy or emissions on computer-controlled gasoline and diesel engines, as long as they were built after the introduction of closed-loop oxygen sensor feedback systems. Modern computer-controlled engines can adjust fuel injection to compensate for a dirty air filter, but carbureted engines depend on air flow for fuel delivery."

http://knowhow.napaonline.com/what-could-a-dirty-air-filter-do-to-your-engine/

You are specifically referencing fuel economy and emissions. In steady state tests like those used for fuel economy, I do agree but performance takes a hit. Under hard acceleration or heavy load, the fuel mix goes rich.

A decrease in performance typically introduces harder acceleration, all things being equal. The long term effects of a rich fuel mixture performance compensation are fouling of the O2 sensor and blockage of the catalytic converter resulting in fuel economy reduction and emission increases.

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Does a Dirty Air Filter Hurt Gas Mileage?

Changing the air filter probably won’t improve fuel economy with modern cars. When we tested a car to see whether a dirty air filter hurt its gas mileage because of reduced air intake, we found that the car’s acceleration was hurt but not its fuel economy.

The engine’s computer automatically compensated for the restricted airflow by reducing fuel use to maintain the right air-fuel ratio. We expect similar results after any air-filter change.

https://www.consumerreports.org/fuel-economy-efficiency/how-to-get-the-best-fuel-economy-now/

[kamakazi]

Fuel economy, emissions and performance are not mutually exclusive.
In a modern vehicle with closed-loop feedback systems:
Under hard acceleration or heavy load, the fuel mix goes rich.... but doesn't exceed what the ECU is capable of
In those systems, Fuel is injected based on available air, not the other way around. With a clean filter or a dirty filter, both will run rich temporarily for the duration of the acceleration event.

Your argument might then be because one has to accelerate longer to get to the desired speed they will be running rich longer; yeah but using a similar amount of fuel in the process ("because the fuel economy remains about the same between dirty and clean air filters and this is due to the fact that they are using tables in the ECU").

If however, you are saying with a dirty filter you will be accelerating all the time well that is a different story entirely, but realistically how much of a difference in performance do you feel? Should get someone to randomly change the filter to a new one without your knowledge of when. Would like to see anyone identify when it occurred due to the increase in power that they felt. Not saying it is impossible but it would be interesting to know if someone can feel that difference

and back to my earlier point, I am not going to generate any more soot with a dirty air filter vs a clean one in a modern vehicle with closed loop controls.

On a carb vehicle or one with open loop controls, this is a different story. It doesn't know anything about air filter, oxygen sensor, MAF, MAP....nada.

edit:
As i think about it your right foot as more control over soot generation than anything else in a modern car

[adnj]

You are oversimplifying somewhat but I suppose that you could visualize it by considering how far do you need to depress the accelerator to reach the same velocity in the same distance with cars that are essentially similar except that one has twice the horsepower of the other?

A dirty air filter doesn't typically change your fuel economy or emissions levels when the vehicle is cruising down the highway - the driver does because of the decrease in the ability of the vehicle to reach cruising speeds.

[sMASH]

came across this pretty interesting walk through of the oil system.

[VexXx Dogg]

^ excellent vid. explains it thoroughly. I def learned some new stuff!

At about 3;48 man said JOOK yes.

[eitech]

Interesting point he made at the end with the position of the plug. If you don’t jack up the car properly u wont drain all the oil from the sump.