Another Oil Question

[ISP197]

Not trying to start a "best oil war", just trying to get ACCURATE information. I have a V8-270 C-B, cat motor. I usually just run the recommended Volvo 10w40 oil, but it is getting extremely hard to find in my area and very pricey. The manual recommends any high quality oil 5w30 or higher (10w30, 10w40, 15w50, ect.). I have thought about using Mobil 1 15w50, as I can get it easily, but have read it has a high Zinc level. I have read that oils with high zinc levels should not be used in Cat equipped motors. Is this true? Also, should I just pick a good quality 10w30 synthetic and call it a day? My other option would be to get a good quality synthetic 10w40 in a "High Mileage" oil, since that viscosity seems to be only in "High Mileage" for synthetic oil. Will the seal conditioners cause problems now or later if I go that route? I know I am probably overthinking this, but any advise is appreciated.........Thanks

 

[Scott Danforth]

if your motor has cats on it, it is a roller motor. no need for high zinc

and yes, high zinc is not good on cats

 

[ISP197]

Okay........So the Mobil 1 15W50 is out. What about the other options? Would you recommend synthetic 10W30 or "High Mileage" 10W40 synthetic from a reputable brand like Castrol or Mobil 1?

 

[Lou C]

I don’t think any grade of Mobil 1 has high zinc remember it’s a car based oil and cars have cat exhaust right?
if you can find it easily you can use the Merc/Quicksilver 25/40 it’s a marine rated oil approved for cat exhaust

 

[Lou C]

Really if you look carefully even diesel oils do not have high zinc any longer they are in the range of 800-900 ppm like gas engine oil. The only truly high zinc oils are specialty oils for racing (Valvoline VR1), oils for hot rods and classic cars and some specialty oils like those made by Lucas Marine.
I’ve had good luck with the regular Merc/Quicksilver 25/40 which has about 850 ppm of zinc based on the Blackstone analysis I did. Mine’s a roller cam motor so high zinc is not needed.
Even with the one flat tappet cam motor we have (‘98 Jeep 4.0) running it to nearly 180,000 miles with conventional oil not high zinc with no problems at all.