I usually go by my oil pressure. I can tell by the pressure reading when it is getting bad. The oil life things tells me to change it when idle pressure is at 38-39 psi hot. With fresh oil, idle pressure is 43-44. I usually change it when it gets to 40-41.

Mobil1 Synthetic all the way! Some things you shouldn't skimp on .. and engine oil is one of them.

 

i run castrol 10/30 full synthetic change it 4,000 miles

 

I change it when I see the color changing. Like a darker brown usually. I don't go by milage. That oil life monitor is off usually for me. That happens 4000-5000 miles usually

I like to run Mobil 1, it goes in the WRX. I use Valvoline 5W30 in the Z, and 20W50 in the ol' Blue Oval as the rear main leaks...

 

I have noticed the Mobil1 is a little darker to start with, so I don't know how reliable the color method would be with that.

I used the Oil life once, and it was BAD looking when I did change it.

 

I run way too many highway miles to change it every 3000 miles. I usually go 6-7000 miles on Mobil 1 10W30. I can tell when it's time to change by how loud the tapping noises are.

 

6500 last time one mobile 1 15/50....so far only 540 on this change...but i'll probably change it once it gets really cold down here just for the hell of it.

 

regardless of time, money, effort, i still go by every 3000 miles. I guess it's habit.

 

run royal purple 10w/30. change every 6k and change the k&n oil filter every 3k

 

Mine averages 3800 miles. If I'm on the top end of that and have been playing hard, I'll change at 3k. If I have been running mainly highway miles, I'll go 4k - 4.5k Mobil1 5w30 year round and A/C PF59 filter.