WAC

There's been lots of discussion recently on the 2 year and 20,000 service interval. But I'm just curious what everybody thinks the oil change interval ought to be. Porsche says 20,000 miles. Obviously, if you track the car, or never drive, you might think that's too long.

I change the oil in my other vehicles between 3,000 and 5,000 miles. But I'm not running Mobile One in them either. They all have much longer service intervals than I follow, but I think new oil is cheap insurance - and it can't hurt.

With respect to your 997, driven on the street, or with only very minor high performance driving, at what interval do each of you actually change your oil?

MrBonus

Prepare for a lot of unsubstantiated conjecture about when and why you should change your oil.

1999Porsche911

Oil is a cleaner and in the process of cleaning, it is holding contaminants in suspension. Acids also accumulate in the oil. Outside dust and other particles get into the oil through the intake system, further contaminating the oil. Therefore, how long the protection properties of an oil last are only a small part of what determines when an oil should be changed.

Therefore, a 20,000 mile recommended oil change interval orginally suggested by Porsche is wrong and was issued for no other reason than to be "green". Since this recommendation was issued, Porsche has begun to realize how wrong they were and lowered the interval to 15,000 and will most likely be lowering it again before too long.

IMO, a primarily street driven engine needs an oil cgange somewhere between 5,000 -7,500 miles. Dustier areas, such as planting season in the farm belt, would require more frequent changes.

Porsche has a poor history when it comes to determining which oil to use and when to change it. It is far better to do some research on your own than to rely on their recommendations in order to determine which oil to use and the frequency of oil changes best suited for your driving conditions.

911Dave

It appears you hit the nail on the head!

fskof

I agree with you 100%. A few engineers have told me that you should always subtract half of what the manufactors recommended oil change interval is. If a owners manual says 20k than do it at 10k and so on. This rule applys to all of the fluids in every car!

The reason manufactures are going with these long fluid change intervals is because it lowers there Maintenance to operate costs. Companies such as BMW that include FREE Maintenance with every vehicle can save Millions by streatching out fluid changes. Bottom line its all about saving $$$$$$$

MrBonus

I heard from an engineer that you take the recommended oil change interval, square it, multiply it by .74 then take the square root, then subtract the number of touchdowns Joe Montana threw in his post season career (Multiplied by 10, of course) and then divide by pie.

Only then do you know the true fluid change intervals of a car.

helispud

So we need to change oil every 5,333 miles!

MichaelL

A 5,000 to 10,000 mile oil change range is reasonable for a car that is driven, assuming synthetic oil. Once a year for minimally driven cars. Cars that are essentially stored unused, less than 2,000 miles, probably once every two years.

911Dave

My engineers told me the same thing, except they said divide by apple pie if the car is domestic, but rhubarb pie a la mode if it's foreign.

joninoc

You have to change the oil on these things?

InTheAir

No, because they're water cooled.

jnx

Pie ?

sharmat

i think he ment pi (as in 3.14....)

tkids

When it makes me feel good! 5-10k

joninoc

3.14159