Burning oil, would mid SAPS be easier for catalytic converter?

Feb 18, 2015
My car is burning oil about 0,5 l/1000km (1 quart per 1200 miles). It’s been steadily growing as the engine gets more kilometers on the clock.

I’m going to clean up the PCV valve and do an engine flush, as I have had some slight help from these previously. But clearly the engine is just wearing out.

My car is 2005 Nissan Primera with 4-cylinder naturally aspired 1.8l gasoline engine, 325 kkm on the clock. I’m planning to drive the car as long as it drives well, up to 500 kkm, when it’s time to change for a fresher car.

Manual states that full SAPS 5W-40 (ACEA A3/B4) is the correct oil for it, and that’s what I have been using. But I’m starting to worry about my catalytic converter with this rate of oil burn.

Would mid SAPS oil be helpful for the longevity of the catalytic converter, to help me get to the 500 kkm with the original converter? Are there any adverse effects on changing from full SAPS to mid SAPS oil, ACEA C3?
It would depend how the oil is consumed. Through the pcv system means the chance of consuming phosporous is quite low, but if oil is lost through the compression rings or valve stem seals you will consume phosporous.

Also, if the engine is leaking oil, that also means no phosphorous being sent to the catalytic converter.

So C3 or C4 oil could be of benefit, but just by how much is the question. C3 means phosporous is limited to about 800 ppm, while A3/B4 goes up to 1200 ppm.

I have observed faster oil breakdown with C3 oils versus high quality (synthetic) A3/B4 oils, but if you burn 0.5l/1000 km the oil will never be old in your engine anyway. Keep an eye on oil consumption after switching aswell, the rate could also go up.
I'd actually look into lower saps oils still and I wouldn't be afraid to go to a 50 grade if an 05 states a 40 in the manual. It's old and worn enough to at least merit a test. Now how are the emissions in your area. Is it required for the vehicle to be allowed on the road. In some places you can just let the cat die and it wouldn't matter.
Yes, we have mandatory yearly safety inspection which includes OBD2 reading and a tailpipe measurement. So, it’s definitely a failed test and a new cat when the original one gets exhausted.
One of the lower SAPS HDMOs might help. The CJ-4 and CK-4 or ACEA -9 are low SAPS and tend to help gas engines with burning issues.
Perhaps look into Delo 600 ADF. It may be unavailable in Finland. It's super low SPASH with almost none of the cat/dpf cloggers in it. SA is only 0.4. Sulphur is 0.2.
It comes in 10w-30 and 15w-40.
I didn't remember that C3 oil has less TBN than A3/B4, and I guess that's the biggest difference between their performance. But, as stated above, it doesn't matter in my case as the oil gets replenished constantly with new oil anyway.

Usually all C3 oils sold here are 5W-30, but I managed to find one C3 oil in my region with 5W-40 grade.

So, my next candidates are:
1) Mobil 1 FS X1 5W-50 A3/B4 & MB-Approval 229.3 => Thicker
2) Castrol Magnatec 5W-40 C3 & MB-Approval 229.31 => Lower SAPS

Thanks all for your feedback!
Your rings/valves seals must be damaged or sticked.
I would go with M1 5w50 and ring treatment.
PD: Valvoline Maxlife too.
Yeah, I suspect it’s the gummed up rings + normal wear and tear for this mediocre quality engine. I’ve tried Valvoline MaxLife already, but it didn’t bring any changes for the oil consumption (or maybe even inreased it a bit).

Don’t have time for piston soak as it’s my daily driver. So, engine flush + M1 5W-50 is what’s coming next. Will try Castrol Magnatec next summer, as I’m curious to see if the consumption is practically equal also with the C3 5W-40 => Would then prefer the lower SAPS oil to save the cat.