Re oil and cat converters
 

Ok MY BAD YOU ARE CORRECT.I didnt take the pcv stsem into consideration.Like I mentioned I wasnt aware of this so yes you taught me something I didnt know.I did not find though nhow oils with high zinc content affect the converter just that using the wrong type or wrong viscosity oil can cause damage.I would consider a oil that promotes less engine ware as the wrong type of oil.Also these high zinc content oils are very new on the market so I would say you cant conclusively come to the conclusion that using a high zinc antiware oil will adversly affect a cat converter.I use high zinc motorcycle oil in my truck 15w40 I run higher oil pressure than comon dino oil.I dont care if it cost $20 a gallon.

Here's a quote from Wikipedia:

"The main use of ZDDP is in anti-wear additives to lubricants such as greases, gear oils, and motor oils, which often contain less than 1% of this additive. It has been reported that zinc and phosphorus emissions may damage catalytic converters and standard formulations of lubricating oils for gasoline engines now have reduced amounts of the additive, though diesel engine oils remain at higher levels.[3] Crankcase oils with reduced ZDDP have been cited as causing damage to, or failure of, classic/collector car flat tappet camshafts and lifters which undergo very high boundary layer pressures and/or shear forces at their contact faces, and in other regions such as big-end/main bearings, and piston rings and pins. Roller camshafts are more commonly used to reduce camshaft lobe friction in modern engines. There are additives, such as STP(R) Oil Treatment, and some racing oils such as Brad Penn and Valvoline VR-1, which are available in the retail market with the necessary amount of ZDDP for engines using increased valve spring pressures. The same ZDDP compounds serve also as corrosion inhibitors and antioxidants."

Oil companies are developing new additives for anti-wear that contain other chemicals and minerals that do not harm cats. Bobistheoilguy.com is a good source for oil study.

Good info! I guess there are oils that are better suited for specific (classic vs modern) applications.

Yes, there are. That's a major reason for the designations SL, SM, SN, etc.

Thanks for that informitive info,I may have to rethink what oil Im using

I have never done this personally, but does anyone use say a full synthetic motor oil then if you're a quart low down the road, put a quart of conventional in? So essentially mixing full synthetic and conventional?

Yeah, that's perfectly fine.

FWIW most "full synthetic" oils are not even close to 100% synthetic. They are hydrocracked group III dino oils... so that 1 QT of dino oil you add at the gas station really isnt changing much.

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And the synthetic blends aren't really blended at all with 95% dino lol.

Great topic! I have never used synthetic in any of my Jimmys due to the fact these engines love to leak oil at higher mileage and a synthetic will find a way out faster than a petroleum base and I have also never used synthetic in an engine I didn't buy new or rebuild-Too many risk factors to list here. I run Valvoline 10-30 year round and have lately been running up to 5k on changes as all of my operation is at highway speed and my 206k unit uses 1/2 qt in that time,where my Lincoln uses a quart every 1000 miles with only 65k on it! But Fords have always used oil at a higher rate and last just as long!

Pennzoil 10w/30 for winter
10w/40 In the summer