Engine Oil Discussion
When I was young, a long time ago, I bought a 64 Dodge that had a Poly 318. It used oil. I tried all kinds of oil at the time, all the big names, and then I tried Valvoline racing 20w50. That engine started burning less oil and eventually only burned less than a quart between changes, at 3,000 miles. I put over 100,000 miles on that car and it was running fine when I sold it to buy the 64 Barracuda. No idea why, I was not into building engines till the 64 Barracuda. I have tried most oils over the years, I remember trying a light weight Mobile 1 when it came out with all their claims. Put it in the 273 and ran it hard. I didn't like the hot idle oil pressure and the way the engine sounded. Drained it right out, after that drive, and went back to Valvoline Racing 20w50. I run Valvoline synthetic 10w30 in the three 5.7 Hemi's we have now. Both the Chrysler and Chevrolet Racing manuals state that straight 30 oil will cause the least wear of any oils. That may dated now. Chrysler Racing also stated that they tested synthetic oil and saw no benefit. As for ZDDP, it is my understanding that the zinc can clog catalytic converters so our "brilliant" leaders have banned it from the latest SAE oil grades. I have no idea what the oil companies have replaced it with. However if your engine does not burn oil, the catalytic converter will not clog? I have a 96 ACR Neon with 250,000 miles on it. I ran either Valvoline Racing straight 30 or 20w50, that have plenty of ZDDP, in it it's whole life. I still have it and it runs like new and has the original catalytic converter. So, I recommend good oil with ZDDP conventional or synthetic for flat tapped cammed engines and change it more often than the recommended intervals with a good filter. I also know you have to do what you need to do, but cars are an expensive item and the cost of good oil is relatively cheap. I won't tell you what good oil is, there are many out there.
Let’s see if I can do this without offending you.
1. There is never, ever a reason to run a single grade oil. Ever. The Viscosity Index Improvers since the late 1970’s have been improved. So has the base oil.
Any engine oil that is multi-grade (there is no such thing as oil “weight”) starts out its life as the lower grade. A 20w50 starts out as a 20 grade oil and VI improver are added (among other things) so that the oil acts like it’s higher grade at 212 degrees.
Thats why you never saw a 0 grade oil until not that long ago. The VI improves and base oils weren’t good enough to start with that grade of oil.
At one time Castrol made a 10w50. I used to use it. They stopped making it around 1984ish (IIRC) because the bad oil wasn’t capable enough and the VI improvers had issues with that range.
Today, with a QUALITY synthetic oil (that means Group IV and V base oils ONLY) and todays VI improvers you can get a 5w50 and it will outperform ANY single grade or 20w50 in every single test there is.
You can also run a 0 grade base oil (I run either a 5w30 or probably will run a 0w20 this time) which means you can close up the clearances, carry the same oil pressure and get better cooling and protection than you can with a heavier grade oil. You couldn’t do that in the 1970’s. Or the 1980’s.
The “synthetic“ oils Chrysler was testing are not the same oils we can buy today. So that testing is obsolete. So is the advice that single grade oils offer more protection than multi grade oils. They don’t.
The government didn’t “ban” zincdiakyldithiophosphate (ZDDP). As I said above, ALL ENGINE OILS HAVE ZDDP OR THEY ARENT ENGINE OILS. The government mandated lower levels of ZDDP because no matter how good with a bone you are, no matter how good your rings are, there is oil migration out the exhaust. The ZDDP coats the catalyst and kills it.
ZDDP isn‘t just for cams. It’s for the rings, the exhaust valve guide and any other extremely hot, high load parts.
So there is no “BAN” on ZDDP.
There are many middle of the road, will work well enough oils out there. There are very few high quality oils out there. And you don’t find them at box stores and crap holes like Walmart.