What would cause my oil to get dirty faster than normal?

I use mobil 1 with a wix filter and change it every 3k or less. today I just changed the oil at 2500 and it was pretty dark. I realize I drive the car harder than normal, so thats going to account for some, but i still think it gets dirty faster than normal. The oil in my truck doesnt look dirty until 3500, even 4k and its 90% the same engine.

My air filters are kind of old, i plan on replacing them. could this be a cause? my dad thinks my car is running rich because it blows black condensation out the exhaust if you rev it cold. (i dont see how this would cause that though? )

its done this since i bought it at 75k miles 4 years ago, its now at 89.5k the heads look clean (looking from the oil cap) and the car runs strong as hell (see sig). Its never been opened for anything. doesnt burn, use, or leak any oil whatsoever. It also gets fantastic gas mileage, so i dont think it could be running too rich, but who knows?

any input?

 

Dirty turning black isn't an indication of how dirty it is. It just shows its doing its job at keeping the inside of the engine clean and free of sludge and buildup.

 

ok well i guess that makes me feel better. but should i continue to run oil thats dirty at 1500-2000 miles? When i saw the dipstick yesterday it was an instinct to immediately change it.

 

Honestly, I'm not sure about "dirty oil"... there is a place you can send it for analysis (search msgboard) to see if you've got problems... I doubt you do.

Other article I read (also found on here via search) was about Mobil1 and oil analysis... stuff doesn't get to its best condition before 2000 miles, so changing it at 3000 miles seems "too frequent" for me.

Anyway, there's tons of good info available here.

 

someone on another board suggested it might be my 160 tstat - the engine might be running too cool making the computer give it a rich mixture. could this be it? i didnt think rich mixture would make oil dirty, but two people have said things like that.