Freak

I was just about to post when you posted your comment.
You are right.

Something I can add.
The oil filter will not change the color of the oil.(Keep it clear for longer).
The oil filter is there to keep out microscopic metal pieces and also small dirt that can damage your engine.
My other car was also like yours.
I changed oil and at about 1000 to 2000km into the service it started to become darker in color. At 5000km it was black and I changed oil.
I decided to remove the sump and clean it out.
It was not dirty when removed but I cleaned it out anyway.
Put it back on and put in new oil.
It is now driving about 5 to 6000km before it starts to darken.

As Freak also mention, if you drive it hard it will darken more quickly.
Town driving can also cause your oil to become darker quicker.

Try and remove the sump. Clean it out and also as Freak mentioned to make sure check your Air\Fuel.
It can also cause quicker dirty oil.

another solution might be to change your oil at 5000km intervals? its better for your engine and you could retain your oil filter every 2nd oil change to keep costs down if you like...

Town driven and gets a fair hiding. How can i check my air/fuel ratio, i know the ECU has a self diagnosis system with the red/green lights but i cant get any info thats good to me from it.

ANGE i change it, every 5000 with a new filter as well with mobil one fully syn (can anyone recomend a better oil for driving in sydney's conditions) I also keep samples of the oil i take out in glass jars to compare and its cleaner every time ive changed it------also whay engine do you run looked in your album but no eng bay pics, with a body as good as yours i guess it has seen some work too??????

CA18DET ECU self diagnosis is only for faults. See the factory manual for the S13. It's on various websites in PDF format.

A proper dyno tuning session is required to be sure.

If you are running anything aftermarket on the engine, then you can't be sure that the CPU is compensating appropriately for the modifications.

Buy a Nissan oil filter and see the difference. If you haven't rebuilt your engine, then it might still be cleaning up the build up from it's Japanese past. I've heard that it's VERY common for the Japanese to not Service their cars. They don't keep them long enough to make Servicing a concern.

Chris

its still running an a12...

im attending to the interior at the moment then an engine conversion will be done last... probably after the summer when the nice cruising weather is over...

Factory CA18 manual says the oil should be replaced every 3 months or 5000kms.

5W-20 should NEVER be used in hot areas, or for sustained high speed driving.

20W-30 should be used over summer, on the street. And 20W-50 if driving hard over summer.

10W-30 in winter is recommended.

This is all from the factory manual.

Chris.

the only reason oil becomes "dirty"in colour is because the heat and friction of the engine oxidises the oil (or burns it) like when you have a wok too hot on the stove and the oil burns. This oxidisation forms the sludge which blocks oil galleys and can cause ensuing oil changes to be also "dirty" .
The best bet is to run an oil cooler with a remote filter mounting for performance applications and also fully synthethic oil to prevent further oxidisation of the oil underhigh temp ranges. (Fully syn oil has a much higher resistance to high temp oxidisation and willkeepits viscosity and therefore anti frictional properties.)

thanks for all the responses.

And i thought i'd let you guys know that a Nissan oil filter for a CA engine was cheaper than an aftermarket Ryco Z145A filter at kmart. Nissan was $7.80 compared to $12.70 for the ryco. Genuine parts cheaper, since when????