[trshman]

Let me first say I'm posting here because my '66 LeMans has a '70 GTO 400 engine with heads from a '78 TransAm.

For all the 19 years I've owned the car I've used Shell Rotella 10w-40w plus a quart of Lucas Stabilizer per my mechanic and have had no problems with my solid tappet hydraulic cam (Edelbrock Performer).

Recently reading what I'd call a "paper" evaluating over 200 oils and some additives by someone named "540 Rat" I'm now rethinking what oil to use.
This paper claims, contrary to what I've believed until now, that my engine needs the extra zinc found in the Rotella. This "540 Rat" claims that the need for zinc is wrong and that the "psi" rating and how it holds up under higher temperatures should be the only considerations (aside from cost) when choosing an oil.

Is anyone familiar with this guy or have knowledge of this report? In addition does anyone have any opinions either way about the need for zinc in an engine like mine? I'm considering either the Valvoline Full Synthetic High Mileage with MaxLife or the Quaker State Ultimate Durability because of their high "psi" ratings, how they hold up under high temps and cost with both being superior to the Rotella I've used according to his test results. I'm trying to determine if I need the ZDDPlus in addition.

Well that's my problem for today . Any thoughts/help would be appreciated.
Have a good one, trshman

[ponyakr]

If what you're using has worked fine for 19 years, why change it now ?

If it ain't broke, don't try to fix it.

I use Rotella T4 15w-40 in my 455 bracket engine. I've read that it still has a 1200 ZDDP level. Some of the diesel oils meet the SM rating, which have a max of 800. These have wrote on the bottle that they can be used in diesel & gas engines. I've read that this SM standard was established in 2004, to protect catalytic converters.

I realize that not everything you read online is correct.

At WM, I recently noticed that the Delo 400 & the Wal Mart house brand diesel oils had the SN or SM rating, stating that they can be used in gas engines. The Rotella T4 oil I bought does not include an SM rating.

https://www.walmart.com/ip/Super-Tec...7a&athena=true

https://www.walmart.com/ip/Shell-Rot...hoCM-IQAvD_BwE

[Drew W]

ZDDP is $20/per oil change at O'Rileys

Pretty cheap insurance

Just my opinion.

[trshman]

"if it ain't broke, don't try to fix it" is solid advice. It's just that in this "540 Rat" paper the Rotella I use got a rating of "Modest" bordering on "Good" rating plus it began breaking down at lower temps that the 2 I'm considering. Since I'm going to be going back to South Florida this summer I'm concerned about oil temp. Your advice is well taken, eventually I just may leave well enough alone. Thanks for the responses.