Hi everyone. I have a 1998 Maxima 5sp with about 131,000 miles. I have been using Castro Syntec 5w30 since about 70,000. I usually change the oil every 3,000 to 5,000 and I travel about 70 miles a day all highway miles. Here is the problem, from about several oil changes, I noticed that at about 2,000 miles from the last oil change that the oil level is low. I add some oil and check again in about 1,000 miles and low and behold its low again. The car is not leaking oil (No oil spots on the floor), nor can I tell if it is burning oil. So where is it going? The only thing I can think of is that I have been shifting at a higher RPM and sometimes driving in 4th gear while doing about 70 (To get that extra pull). I have a CAI and complete exhaust (y-pipe, cat, b-pipe, and exhaust from Warpseed). Should I change from 5w30 to maybe 10w30? What about switching back to regualr oil? In the past I heard you couldn't do that after using synthetic oil.

Oh by the way, I also have a 1999.5 Pathfinder that has about 150,000 that I have been using synthetic oil, and same happens on the truck as well

Thanks for any input.

 

If it's not leaking, its burning (seeping past valve guides, and/or piston rings).

How "low" is the oil getting between the oil changes? My max has burnt 0.25 to 0.5 qt since I have had it (the past 80miles) - between the 3k oil changes.

 

VQ oil readings with a warm motor blow for accuracy but you'd likely know that already. It'd be worth finding out if your cars smoking at all under load and a friend driving behind you could check that.

My advice is just try a slightly thicker oil, syn or dino. I've never personally witnessed any probs with going back to regular from synthetic.

 

Use 10W-30 and replace the PCV.
Also check the oil pressure switch, you might have a very slow leak.

 

Listen to this guy, he speaks the truth. Only thing I would add is use Mobil 1 full synthetic..