RallyJon

Does the small filter fill up/wear out at a slower rate than the big one?

Edward

From my understanding, the large oil filter is considered the "main" filter for the engine oil. The small one is for filtering the oil to the heads, more specifically the valve train because of the tight tolerances in the hydraulic lash adjusters. From this I presume far less oil flows through this filter media, which suggests why the factory allows an interval twice as long.

My feeling on this matter is that 12-15K miles on a filter "designed" (and I use that term loosely) to filter at 30K mile intervals still offers a comfortable "cleaning margin," if you will.

If there is anyone with direct knowledge on this issue of the small filter's task and longevity, I'd be glad to hear it as I am in no way expressing any points based on hard data.

Edward

Bull

Both filters are full-flow filters, with all of the oil passing through each filter. One filter is in the scavenge circuit (large) while the other is in the pressure circuit (small). The size difference is likely due to the fact that the first filter usually traps more contaminants than the second filter. With syn oil, don't wait for it to turn "black" like dino oil, as it won't.

Once you shorten the factory recommended interval for oil (15k) and filter(30k) changes, it is up to the individual as to where to stop. I too find it interesting to see the rationalizations explained.

Slow Guy

And so you're saying that by not changing the filters every time on a car that gets 3,000 mi. between changes that we're shortening the lifetime of our engines? Do you have proof of that?

Maybe it's just that I'm not hung up on replacing something that doesn't need replacing, it has nothing to do w/ the cost of filters.

CentralCoastC4S

I just went through all of this discussion in my head and went ahead and changed the oil and both filters on my 993C4S. It had been more than a year, far less than the recommended miles but I was not comfortable with the time
between changes. I live in an area where it's often hard to get the car up to full temps, even after driving for a while. I assume I'm getting some condensation in the oil as a result. Also, look at the oil system diagram
in the factory manual. That little filter is in a fairly important part of the oil system. If I'm reading the manual correctly, it's in the system that also includes the lifters, the cam spray bar and the crank squirters. Is that correct?
If so, why not change that filter everytime you change the other one. It's not
that big a deal, get the right wrench, remove the rubber ducting hose and the
oil return line and you are there.
I agree there is no point in wasting money on oil and filters too frequently but I've always thought that on cars that get driven less than frequently, may not always get up to full temps- change the oil at least once a year.
Found my Mobil 1 15-50 at Target, not cheap but at least they have it.

pedsurg

What about the flip side of this issue?? Change the filters per facory spec but replace the oil alone, MORE frequently as described above.
Thanks
Jack

Bull

Then why change the synthetic oil at 3,000 miles, or do you believe it needs replacing?

Slow Guy

Simply because I like to change the oil once a year at least. I drive the 993 apx 4k per year. However, when I do drive the 993 it's for longer drives and the oil gets a chance to warm up completely. I don't like doing short grocery runs with this car, I have others for that duty.

Edward

FWIW, it's generally accepted (by many wrenches, if you take stock in that sort of thing) that low annual-mile/low-use cars should have their oil changed annually, regardless of mileage. Water content from unburned condensation is no good for the load-bearing surfaces within the engine, nor is it good for the other contaminants from the combustion process to just float around. So even though the oil is often not "used up" in the strict sense, it is no longer as "useful" (or maybe "effective" is better) as it was.

Edward

Slow Guy

I'm no expert but this would make sense to me. However, BMW seems to be moving away from this, at least w/ regard to their "free" scheduled maint. From what I've heard they won't do the oil change unless the "oil service" light is on.

FWIW, when my wife's new 328 comes in I'll not only replace the oil/filter after the first 1,500 mi. (not covered) but also change the oil (at least) every 7,500 mi. (again not covered).

I'm thinking about getting a '02 M3 for a daily driver/DE car but if the PO has only done BMW's recommended maint. I'm not sure I'd want to buy it.

Red rooster

The oil quality can be seriously affected by repeatedly making short trips , even if the milage builds up over a year .
The 911 loves at least a 20 mile trip to get the oil/motor right up to temperature and give the motor internals a good clean out - boils the water off .

Bottom line is that oil / filter change based on annual mileage should have how much long trip mileage is part of the equation !

Geoff

--------------------------------------------------------------------------------
KS400200 , the oldest 964 on Rennlist , unless you know differently !

FLYT993

I change everything every 5k.

However, I will be talking with Chris W. next time I decide to do this because at $300 (parts/labor; $100 for oil & filters/$193 for indie labor) I need to learn how to do this myself. I also find myself driving the car more and more. I don't understand how anyone can have one of these and only drive it 6k/year or less. That's just me though, to each his or her own. I've wanted one ever since I was a little boy, and now that I have one, I intend to enjoy it. I never put her on the road for less than 20 minutes, and always take the long, long way home just to have more seat time.

Edward

BMW is not alone in this. More and more manufacturers are going with longer service intervals. Reason is simple: cost. If the car has "free" service, the savings is obvious to the dealer and mfr. But manufacturers also want to use the "see, our cars need less maintenance" angle to help sell their cars ...not only on the showroom floor but also as fleet/business vehicles. Who cares if the car's mechanicals are stressed; the service cost is reduced! BMW even has the "sealed for a lifetime" transmission fluid. Yeah, I'm sure that super-duper teutonic oil is perfectly fine at 100K miles.

Edward

Dick in TN

Our family car is a '97 BMW 540i that we bought with 30K miles, now has 130K.
Transmission fluid never changed, as it is lifetime fill, and operates perfectly.
Engine oil changed per the service light, which is 12 to 15K, with Mobil1.
Have never needed to add oil between oil changes.

JasonAndreas

Another reason is that most new oil level sensors can also measure the condition and quality of oil and not just the level. Mercedes Benz has been using a simple version of these since MY98 while the new'n'improved sensors are starting to show up more frequently in other european cars. The North American based manufacturers have been calculating oil condition based on your driving habits and data from multi-million mile driving tests since sometime in the mid to late nineties.