I switched to Rotella tonight and noticed my AFR's changed from 14.7 while cruising to 13.7-14.0. Anyone ever heard of something like this happening?

 

did you disconnect the battery before changing the oil?

 

1) who ever does that

2) changing oil should not affect AFR as far as I know



Keep an eye on it. Do you always use the gas station?

 

1) I have never in my life heard of the need to disconnect the battery when changing the oil.

2) Stocker: What do you mean do i always use a gas station? Its not like i have a refinery in my back yard o.O If you meant the same gas station, no. But the AFR's were the same before and after I filled my car saturday.

 

What you need to check is the short term fuel trims. If they are out of whack that would explain the AFRs in closed loop. If they are normal I would suspect the WBO2 sensor.

 

how would i go about doing that?

 

About any OBDII scan gage will read the numbers. The Ultragage though a bit cheesy does a good job for the money.

 

Where should the trims be at? Ill be grabbing a scanner in the next few days then. my airbag light just came on after flashing the car back to stock to see if that was the issue. Trying to burn through this tank of gas to see if that wasnt the problem as well.

 

If they are working properly the STFT should go from a - value to a +. If you are really running 14.0 in closed loop it would stay high and positive.

 

why ask who does it, the OP is under the impression oil changed your AFR.



the only reasonable explanation i could come up with was you disconnected the battery, thus resetting LTFT, but cross it off the list.