Recently picked up 03 I35 with 127K. No oil leaks top or bottom, however she would go through 1-1.5 QT of Castrol GTX 10W-30 dino oil in 250 miles or roughly one gas tank. Stock exhaust and I'm assuming that the pre-cats are original as well.

Installed new OEM PCV valve (The one on the engine was covered with oil, but not stuck), added an inline ADDW1 closed loop oil catch can, and poured 4-1/4QT of Penzoil 10W-40 dino oil into the motor and I'm happy to report that 250 miles later the dipstick still shows right under the high mark.

Not sure what type of oil was used by the previous owner, the car does have a pretty good CARFAX history of regular oil change. I'll keep an eye on the consumption and either stick with the dino Penzoil 10W-40 or try Rotella 5W-40.

Also, going to re-mount the catch can to a more suitable location.

 

Update,

At 340 miles the oil level has dropped slightly below the H mark. The oil consumption is still present, but at least it's little bit more manageable.

Curious if the consumption would be reduced even more with a vented catch can VS a closed loop.

 

Better get rid of the cats before the inevitable. 150k is usually about as long as you get before disintegration starts.

 

Thanks for the replay. I have searched for oil consumption posts and the pre-cat disintegration was mentioned by you very often. I will be looking into it over the next couple of weeks. I am in CA and have to pass a smog check every two years. The smog stations conduct a visual inspection under the hood and under the car along with ensuring that all emissions related monitors are set. I might have to find a suitable aftermarket pre-cat that will bolt on in place of the OEM one.

The car is clean, and it drives fine, my son uses it to commute to school and work/gym and for a moment we thought about putting it back on the market and cutting our losses since it was going through oil at a very high rate. We are still monitoring the consumption, but running 10W-40 dino Penzoil, a closed loop oil catch can, and brand-new OEM PCV valve seemed to get the excessive consumption to about 1/4 of a QT per gas tank fill up or roughly 230 miles.

Curious to know if switching from closed loop PCV oil catch can to a vented one would reduce the consumption even more.

 

Just gut them. It's easy with spade bit (unless bolts heavily rusted). Front one falls out half the time for me
If they're going to catch O2 sensor spacer, then you can wire in a simulator. Worthless govt cracked down on those, but you can build one yourself if you can't find em for sale.

 

yea O2 sims i have not see much past couple years, here and there but yea, i would guess most shops may not notice the O2 extenders, but for sure not any hidden sims. If i were to do it again I would do extenders, seems like more durable vs a computer chip.

 

I always thought about experimenting with a sleeve that covers most of the holes on the sensor to mimic a spacer.

 

My 03 5.5 has same mileage, similar consumption, vented catch can. I use BG 109 and MOA to help with seals / rings. Not sure if it really makes a difference. Make sure tube seals aren’t leaking, especially #5. Big issue on my VQ, accounted for up to 1/2 my oil loss.

 

Thanks for the info. Valve cover gaskets are on the list, even though there are on external leaks. Have you noticed any difference between closed and vented catch can set up?

 

Never tried a closed catch. Used a vented sys for years and works well, very little blowby overall. If you have yet, examine ALL your coils for oil. Yes it means pulling the plenum, but an important step to diagnosing your oil consumption. Typically one or more culprits RINGS VALVE SEALS or GASKETS.

 

Thanks for the info on the vented catch can set up. Right now, with a closed loop, it's catching about a 1/2 shot glass of nasty, oily blowby every 300 miles.

 

230k Oriellys PCV valves are the only ones I have had any luck with. It cleared up 80% if my oil consumption. Pre Cats braking up is bs as far as my car is concerned. I use a sealed catch can to monitor the oil consumption.

 

Could you elaborate on why do you prefer Orielly's PCV valve? I bought one from AutoZone and it seemed very cheaply made and decided not to use it. Went with OEM PCV valve instead.
Do you have any other recommendations for reducing the oil consumption?

Thanks!

 

I've had the OEM ones fail in a couple months, I've tried ones on Amazon and possibly Napa. And as I just the last ditch effort I bought one at O'Reilly's and all of a sudden my oil consumption was very small. And at some point that PCV started using a little more oil and I bought another one and replaced it and it's been several months and it's still working like a champ. I had a very bad leak at the oil pan gasket that was only leaking when you were driving. I've also replaced both cam sensors with worn out O-rings so now nothing is dripping and I would say I'm adding one quart every other month. I'm not trying to convert anybody but I do use Amsoil I had very little success with Pennzoil platinum and Ultra Platinum.

 

Thanks for the replay. I wonder if the aftermarket PCV's are more restrictive and allow less oil to pass through them vs the OEM PCV.

I do have an aftermarket PCV valve that I picked up from AutoZone and I'll give it a try. My son's 03 I35 with 130K runs fine, no lights, no smoke, passes CA smog check, no major leaks from either valve covers. But she goes through a 1/2QT of oil in roughly 250-300 miles.

 

The valve cover replacement helped years ago but I am still burning about 1/4 of a quart down from about a full quart of 5W-30 Castrol High Mileage Synthetic Blend every 200 miles.

 

Have you considered using a 10W-40 oil at least in the summer?

 

Maybe I will give this a shot after the winter. What brand do you use?

 

Use the Penzoil traditional 10W-40 oil. Buy it from Amazon for $22 for a 5QT jug.

 

Thanks. I added this to my list for the spring.

 

nice!!

 

Same here. 2000 miles later and it was junk.