"im never changing my oil" thread discussion

[pmckechnie]

I am the one that started the original post that started this whole thing. The topic continues to hinge around mileage. Mileage is only a part of the formula for when to change your oil. Long haul trucks spend a lot of time on the interstate systems while some others stay in town for short haul deliveries. Some cars spend a lot of time on the interstate system and others stay in town for short trips. Big rigs hold 40 quarts or more oil and have BIG oil filters. My diesel holds 7.5 quarts and a small filter (in comparison). My diesel is used for short trips. I would like to hear how often you change your oil AND what type of driving you do. The manufactures recommend you change your oil at a certain mileage. Then they mention severe service and tell what that means. The mileage interval for severe service is usually 1/2 of the recommended interval for normal service. I personally look at how many of the severe service items apply to my driving and adjust my mileage accordingly. For instance, I make short trips, the trips are in stop and go traffic (city), engine never gets warmed up, some of this driving is in very dusty conditions. I change my oil every 1000 to 1500 miles. Some recommended that I make the trips longer so the engine gets warmed up but that takes time and fuel. I do take it out on the weekends for longer trips which helps but still the M-F driving is killing the oil. It is the moisture and acids that form that hurt the engine, so I get them out more often. Think about it. Oil is cheap compared to engines. And NO I can't walk or ride a bike to work.

[CozyGuy]

Detergent additives clean soot from engine parts, turning oil black. Diesel engines put more fuel into the oil than gasoline engines. Gasoline burns faster than diesel fuel and leaves less residue following a power stroke, and diesels have much higher compression. Both contribute to diesel fuel finding it's way into lubricating oil.

Diesels depend on the added lubricity of fuel. That's why Ultra Low Sulfer needed lubricity additives. Biodiesel actually helps in this, because it has a higher lubricity. It is sometimes used in ULS as a lubricity agent, like in Europe and Minnesota.

The reason for changing the oil is that the suspended soot will turn into sludge when detergent oil becomes saturated, or if left sitting for extended periods. This crankcase sludge can clog journals and inhibit proper lubrication. The interval can be much longer, however. In other countries, it often is.

Some engines actually require frequent changes to operate properly. The Saturn S engines use engine oil pressure to ratchet up the timing chain tensioner mechanism, and 6000 mile intervals may, over time, cause a timing chain failure. This is unusual, though.

If you use biodiesel, some people think it mixes poorly with engine oil, and actually contributes to sludge. From

http://www.biodiesel.org/pdf_files/Biodiesel_Blends_Above%20_20_Final.pdf:

"High levels of biodiesel present in the engine oil may polymerize over time and cause serious engine oil sludge problems. Engine oil change intervals may need to be shortened significantly if using high blends of biodiesel."

Because I use homemade B100, I change my oil frequently. I want my cars to go a million miles.

Regarding injection pump issues, there is fire behind the smoke. Mostly, damage is related to low-quality fuel. I don't know anything about American vs European pumps, other than Europe has been dealing with biodiesel for a longer period of time than most of us, and they have more diesel passenger cars. Here's a pretty good discussion of biodiesel engine/pump issues:

http://journeytoforever.org/biodiesel_FIEM.html

One of my diesels is a motorhome, and it has a very large sump as well as enormous oil filters. The recommended change interval is 15,000 miles. It's pretty much the same Cummins ISB found in Dodge pickups which have a smaller sump and filter and recommend much shorter intervals.

-- Len

[cjlipps]

A lady that worked for me didn't ever change her oil. For whatever reason, I don't have a clue. The car was a 1990ish Ford Taurus. It lasted 70,000 miles before it failed and the engine didn't come apart, it just wouldn't run and a mechanic figured out her problem and she got rid of the car. It was only then I was made aware of the situation. I wish I would have known....
As a side note, I am a firm believer and a 20 year practitioner of full synthetic lubricants and extended oil change intervals. FWIW.

[Hatterasguy]

The problem with these engines is the soot loading. You can go 13k miles in a new CDI without any issues. From what forum members have observed via oil tests it seems that.
616/617's are good for about 6k-8k miles.
603's about 7k-10k.
606's you can stretch them 10k-13k.

Note you can only extend intervials with a true synthetic, like Delvac 1, Amsoil etc. Try it with a dino oil and you will blow the engine up, as MB dealers found out in the FSS lawsuit.

[P.E.Haiges]

Cervan,

Didn't your English teacher ever tell U that U are supposed to start a new sentence with a capital letter?

P E H

[vstech]

as to the soot loading of the various engines.
I wonder why the newer ones don't soot as much.
do they burn that much more efficiently? or are the pistons/rings that much tighter? could the rings in a 617 be replaced with tighter rings? what would be needed to make the 617 a more efficient burning motor?
john

[Hatterasguy]

Originally Posted by vstech

as to the soot loading of the various engines.
I wonder why the newer ones don't soot as much.
do they burn that much more efficiently? or are the pistons/rings that much tighter? could the rings in a 617 be replaced with tighter rings? what would be needed to make the 617 a more efficient burning motor?
john

They burn cleaner. Not to mention have a totaly different head design, and in the case of the CDI different injection system as well. Their is less wasted fuel injected into the cylinders. Computers can do a lot, like pulse the injector 5 times per combustion cycle.

That is why an E320 CDI gets mid 30's to low 40's and a 300D with a 617 gets mid to high 20's. Consider that the CDI weighs a lot more, and puts out almost three times the power. A lot has changed in 25 years.

[CozyGuy]

Diesels have been evolving for years. The three biggest changes were valves per cylinder, injection method, and turbocharging.

Going from two to four valves makes the engine breath better by enabling more and faster intake and exhaust flow. I think this happened around 1993. It improves combustion by making more oxygen available, and more completely exhausting combustion gases.

Injection method is the real biggie. Early Mercedes, as other older diesels, used indirect injection. That means fuel is injected into a pre-combustion chamber from where the burn spreads. This was done so as to make flat-topped and therefore cheaper pistons possible; make mixing fuel and air easier; and enable lower injection pressures. Coincidentally, it also makes engines much more tolerant of fuel variations. These older engines were said to burn almost anything from alcohol to motor oil, at least for a little while. It demands an efficiency cost, as there is greater area for heat loss and the gaseous expansion in the pre-combustion chamber generates no power. These engines are smokier and less efficient than modern equivalents. They also had only two valves per cylinder.

As injection pump technology improved, direct injection became cheaper and spread to passenger cars in the 1980s and 1990s. It had been used in commercial vehicles since the 1970s. At first, it was mechanically timed using cams or timing chains. It has evolved with computer technology and improvements in materials to the modern Common-rail Direct Injection (CDI) that now electronically meters fuel at upwards of 1000 psi. Although this technology has become ubiquitous, it's called different things by almost all car companies. I think Mercedes implemented CDI around 1997.

The big deal about high pressure injection has to do with atomization. Low-pressure injection results in coarse droplets and poor combustion, leading to dirtier engines and more fuel residue to work it's way into the lube oil. Fine atomization allows more complete combustion, and electronic timing using solenoid valves allows precise metering. Some engines even pre-inject a very small amount to prepare the combustion chamber so that it will be even hotter than the compression event has achieved. Then, the rapid, high-pressure injection of fine spray will encounter a still-highly oxygenated and very hot environment in which to burn.

Turbocharging makes air intake and sometimes exhaust more complete by tapping into energy otherwise lost by placing a turbine in the exhaust stream. A cleaner environment during the power stroke means a better burn. Starting with a small amount of compression from the forced air input means higher compression with less effort. Obviously, if the piston travels closer to the top of the cylinder, there is a smaller combustion chamber and higher compression, but getting there by using a turbo and exhaust gas instead means better efficiency.

Other, less important changes have happened. Manufacturing and materials technology have improved, so that engines today are made to closer and more uniform tolerances, at least where it's important to do so. Ring technology has changed. Synthetic oils were a tremendous improvement over detergent petroleum oils, which were themselves a huge improvement over non-detergent single-viscosity oils. Fuel keeps changing; I hate this ULS crap, although it's obviously a lot cleaner burning. We need a better source of veggie oil so we can get away from petroleum as fuel; that's next.

So it goes.

-- Len

[P.E.Haiges]

CozyGuy,

I agree with most of what U say except the pressure of the fuel injected by the Diesel common rail electronic fuel injection systems. Actually the common rail injection systems use fuel pressure upward of 20,000 PSI. This pressure is created by a high pressure fuel pump and the injectors (similar to gasoline injectors) are electric solonoid operated under control of the computer.

The injectors of the 226 and 603 type engines are mechanical and when the fuel pressure created by the pumping action of the injection pump plungers gets to about 1500 PSI, the injectors pop open and fuel is injected.

P E H

[CozyGuy]

You're right; I should have typed 'bar'- the 1997 Bosch common rail was 1350 bar, not psi. Bosch's upcoming 4th generation common rail may be as much as 2000 bar, or a little over 29,000 psi (one bar = 14.5037738 psi). Yeah, that's quite a bit over 1000 psi.

The switching mechanism in the latest generations have moved away from solenoids to multiple layers of piezo crystal wafers, which have the characteristic of expanding and contracting at very high speed. That's what will permit many precise injections per power stroke, instead of a small number of (or even one) pulse.

Hard to imagine, but the combination of extreme high pressure and piezoelectric switches could enable dozens of separate injection pulses during a power stroke, instead of the solenoid max of about 5.

-- Len

[P.E.Haiges]

Len,

I heard of the piezoelectric injectors but I didn'r know they were in production yet.

Yes, its amazing how fast they can operate.

P E H

[Matt L]

Piezo injectors are what CDI is all about. There is a high-pressure rail, but not nearly as high of a pressure as you get at the nozzles.

VW has the PD engine, with a separate camshaft lobe right on top of the injector. No line, and 29Kpsi injection directly into the chamber.

The M-B prechamber systems run at about 15Kpsi.

[dukegrad98]

Originally Posted by P.E.Haiges

Len,

I heard of the piezoelectric injectors but I didn'r know they were in production yet.

Yes, its amazing how fast they can operate.

P E H

I believe Ford is using piezoelectric injectors in the brand-new 6.4L twin turbo PowerStroke.

Cheers, John

[benzforlife]

Originally Posted by dukegrad98

I believe Ford is using piezoelectric injectors in the brand-new 6.4L twin turbo PowerStroke.

Cheers, John

speaking of the new ford,"not trying to hijack here, but"has anyone seen or herd the recall, go to utube and type in 2008 ford recall.

[P.E.Haiges]

MattL,

U are off by an order of magnitude. Injection pump engines run at about 1.5K PSI not 15K PSI.

Is the VW PD engine electronic fuel injection? How do they control the timing?

The old Detroit 2 cycle Diesel engines had the injectors driven by the cam shaft and no injection pump. I don't know how they adjusted the timing, if they even did.

P E H