My son has the base model, 4 Cyl. Well, the car was running rough and after inspection, there was damage to the valves in a couple cylinders. We replaced the valves and catalytic converter. The oil usage is an issue as it uses more than it should. I have heard this is an issue for Nissans. Can someone shed some light on this for me? Long trip, high rpm, more oil usage. Around town, lower oil usage. Still above normal. Any advice would be great.
What do you consider normal?
1 quart every 1,000 miles is considered normal now days.
You did not tell on the mileage your car has, which may help answering your question.
Nissan engines are not bad on the oil burn in general, but since you had valves damage, I might imagine that car has well above 100K miles on it.
It will be likely that valve lash adjustment was never done on this car, as it is PIA and a high cost on Nissan engines.
Imagine you had too small of lash - it would totally explain why valves were damaged.
Now, as bad valves were replaced, did they only replace the ones bad or replaced valve stem seals and adjusted valve lash as head was off the engine?
If not, I would not be surprised that some oil gets past seals and gets either burned or thrown out to the catalyst (which was also replaced, why???).
Sure enough, the engine might be worn on pistons/rings/bores side, once again you did not tell on your mileage to guess if this is normal or premature. Still, I would not be surprised if some wear/damage is present if oil changes were neglected.
That would be my best explanation, also.