# Which oil for a '68 428cui?



## Chris-Austria (Dec 23, 2010)

Hi!

I've the 428 tri power in my GTO.. what kind of oil should I use?
How much is needed with the standard oil pan?
I thought 20w50 or 15w40 mineral oil would be best.. what do you think?

Chris


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## Bensjammin66 (May 12, 2009)

Hi Chris - 

How much oil? I have a '67 400 oil pan on my '73 455 and it holds 6 qts. I am pretty sure they all take 6qts but the one way to be sure is if you have a dipstick installed in the engine well... I wont even finish that sentence. 

As far as what kind of oil that depends on your car. How do you treat the car? Thrashing burnouts on summer days or do you shift 1,2,4 and cruise? How hot does it get where you are? 90s, 100s? More? I find that my engine loves 10-30 Royal Purple. With a high volume pump and a nice day ( 78 degrees say ) I start at 60psi and and drop to about 22-25 at idle once warm. Lots of factors involved here. Determine your driving style and environment you live in and make the decision from there. Most guys on this site LOVE their pontiacs as much as I do. I do not mind a $50 royal purple oil change. My guess, 10-30. But again....


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## geeteeohguy (Feb 2, 2008)

Any 10w-30 thru 15w-40 will be fine, as long as you add ZDDP supplement. I run Rotella diesel spec oil in 15-40 for its higher zddp content plus the additive. Regular, untreated engine oil will trash your camshaft.


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## dimitri (Feb 13, 2009)

geeteeohguy said:


> Any 10w-30 thru 15w-40 will be fine, as long as you add ZDDP supplement. I run Rotella diesel spec oil in 15-40 for its higher zddp content plus the additive. Regular, untreated engine oil will trash your camshaft.


I agree with geeteeohguy.

You can get zddp additive from most cam manufacters or Year One sells it. Don't forget to change your oil every 3000 miles or 6 months.


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## Chris-Austria (Dec 23, 2010)

I don't know what "ZDDP" is, but I'll have to check where I can get it in Austria. Yearone will not ship oils by airfreight I was told. Also the 10w30 isn't available in my region. That would be the same my '01 Cadillac would need, instead of it i use 10w40.

20w50 isn't the correct choise?

In summer we have about 70 to 90 degree and in winter something between 15 and 50. I don't race the car, cruising end enjoying the power sometimes  Maybe I will sometimes drive on the highway 150 miles one way slowly with about 70 mph.. this shouldn't hurt the engine?!

So what do you say? 15w40 or 20w50? (+the ZDDP.. by the way, how much of it?)


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## Chris-Austria (Dec 23, 2010)

I've just read that the Castrol Classic 20w50 has more ZDDP than other oils. So maybe I don't need to add something if I use this one? 
Something about 1200ppm is inside the 20w50 and only 600-800ppm inside of modern oils with api sm classification (because zddp is bad for the catalytic converters..)


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## 68greengoat (Sep 15, 2005)

Here's a link to learn about ZDDP:
ZDDPlus™ - ZDDP Additive for Classic Cars - Agricultural Equipment & More

I run Rotella 15w-40 too in my 455......


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## GTO JUDGE (May 14, 2005)

Chris-Austria said:


> I've just read that the Castrol Classic 20w50 has more ZDDP than other oils. So maybe I don't need to add something if I use this one?
> Something about 1200ppm is inside the 20w50 and only 600-800ppm inside of modern oils with api sm classification (because zddp is bad for the catalytic converters..)


I was using Valvoline racing oil 20w50 with High Zinc additive. If you use the Castrol with zinc in it there is no need to add any additional ZPP Plus.


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## 68greengoat (Sep 15, 2005)

Is it me, or is the "classic" available only in the UK?


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## dimitri (Feb 13, 2009)

20w50 is way to heavy. Do they have a straight 30?


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## geeteeohguy (Feb 2, 2008)

I agree. 20w-50 is too heavy, especially for your climate. 15-40 should be fine.


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## GTO JUDGE (May 14, 2005)

I was using 50W when the car was leaking oil really bad. That with Bars leak brought me some time until the leaks were addressed. Runnin' 30w with the ZDD these days.


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## Chris-Austria (Dec 23, 2010)

I think if I use 15w40 I will have to use the ZDDP additive. The 20w50 Castrol Classic should have about 1300ppm ZDDP inside, I've sent a mail to Castrol Germany to confirm this information from the internet.
Many people here use the 20w50 in their Big Blocks, but I also think that it is too heavy, but I'm net sure.. maybe it's okay because it has enough ZDDP in it?! 

Eventually the 20w50 is only too heavy for use in winter? 
I'll make 2 oil changes every year.. I could fill in 15w40 in october with additive for winter and 20w50 in april for the summer


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## geeteeohguy (Feb 2, 2008)

Chris, again, although the 20-50 has more ZDDP in it, it is THE WRONG VISCOSITY. These cars specified 10w-30 oil when new.


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## Chris-Austria (Dec 23, 2010)

Back in the late 1960's a 10w30 was used?? 
I was also told not to use syntetic oil.. is that correct?
So like you told me.. I'll search for a 15w40 mineral oil and add ZDDP if I find a seller who ships it to Europe


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## GTO JUDGE (May 14, 2005)

Chris-Austria said:


> Back in the late 1960's a 10w30 was used??
> I was also told not to use syntetic oil.. is that correct?
> So like you told me.. I'll search for a 15w40 mineral oil and add ZDDP if I find a seller who ships it to Europe


Personally I think you are making too much of the oil but I understand you're wanting to be precise in what you put in the motor.

10W30 was and still is pretty much the standard. STP oil treatment was the choice of many back then as well. 

Many say its ok to use synthetic some say NOT. According to John Sawruk who was the GTO authority as a GM engineer, GTO historian and the GTOAA answer man, he had said NOT to use synthetics. The outfit locally here who rebuilds Pontiac motors also stated to me not to use synthetics and they install 10w30 in their rebuilds, rebuilds they warrant for 24 months.

If you use 10W30 and put a bottle of ZDD plus in it, you'll be fine. I was using heavier weight because of the oil leak I was experiencing and the car sits in the garage and is rarely driven in cold weather. 

Our standards here are different than Europe, Zinc was banned from standard oil many years ago. I would think there would be oils over there with Zinc in it??

Ship to Europe... A bottle of ZDD runs 9-10.00 here, I googled up this for you I deal with Amazon MOSTLY.. 3 bottles for this is a hell of a deal, shipping is a different story. [ame]http://www.amazon.com/ZDDPPlus-ZDDP-Engine-Additive-Phosphorus/dp/B002TAU52C/ref=sr_1_1?ie=UTF8&qid=1293794768&sr=8-1-spell[/ame]


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## Chris-Austria (Dec 23, 2010)

Hi!
I've read that zddp was banned from american oils, our oils in Europe have still some in it, but it has decreased from 1500ppm to 600ppm. 10w30 isn't available here, if 15w40 will be fine, I'd like to use this. I'll order some ZDDP Plus from ebay or amazon and add a little bit at the oil change.
Thank you!


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## Chris-Austria (Dec 23, 2010)

I've ordered 5 bottles of ZDDP Maxx. (2oz)
The oil I'll use is a 15w40 from Liqui Moly which has 1015ppm ZDDP in it.

How many of the ZDDP Maxx should I use?
I think half a bottle for 5 quarts of oil will be enough because of the 1015ppm of ZDDP which are in the oil itself?!


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## GTO JUDGE (May 14, 2005)

Chris-Austria said:


> I've ordered 5 bottles of ZDDP Maxx. (2oz)
> The oil I'll use is a 15w40 from Liqui Moly which has 1015ppm ZDDP in it.
> 
> How many of the ZDDP Maxx should I use?
> I think half a bottle for 5 quarts of oil will be enough because of the 1015ppm of ZDDP which are in the oil itself?!


ZDDPlus Classic Car Engine Oil Additive - Flat-tappet and High-performance engines
"There is nothing in ZDDP Maxx that was not already in motor oil prior to implementation of the new E.P.A. standards and the introduction of "SM" oils. ZDDP simply brings your "SM" rated oil back to "SF" specifications over 1910 ppm phosphours & 2200 ppm zinc.

ZDDP Maxx is super easy to use. *Simply add 1 2oz. bottle of ZDDPMaxx to 4 or 6 quarts of your favorite oil, *and for racing engines, add .5oz per quart."

Based on that I would think 1/2 a bottle would suffice.


I have 4oz bottles of ZDD plus NOT P-MAX. The directions on the bottle say to use 1 bottle (4oz) per 4-5qt oil change. The site says 2 oz PMAX per 4-6 qts oil. I wasn't aware of ZDDPMax. Looks like you only need half the PMAX than they Plus.


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## dstryr (Aug 27, 2007)

Here's a great article on ZDDP and how phosphorus, zinc and sulfur interact in flat tappet engines.

Corvette Action Center | Tech | Engine Oil Deep Dive - CAC's Comprehensive Look at Engine Oil and Flat-Tappet Camshaft Durability


Also, check out Bob is the Oil Guy. Zinc levels are coming down due to roller valvetrains and effects on cat converters, but not gone. 600-800ppm in most oils. Generally, I understand that 1200ppm on flat tappet cams is the minimum to use, so use Rotella T 10-40 or 20-50 plus ZDDPlus additive.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1791357&gonew=1#UNREAD


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## Chris-Austria (Dec 23, 2010)

@gto judge

That's what I thought... 1oz per 5 quarts will be enough because my "European Oil" has already 1015ppm ZDDP without adding something.
I'll try it with half a bottle ZDDP Maxx everytime I change the oil, 2 times a year. That should get my oil to a correct ZDDP level.. too much wouldn't be good and 1015ppm original is too less.

How much ZDDP is in a modern 10w30 oil like you use in your engines in the US?

@dstryr

Thanks for the article!


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## GTO JUDGE (May 14, 2005)

Chris-Austria said:


> @gto judge
> 
> That's what I thought... 1oz per 5 quarts will be enough because my "European Oil" has already 1015ppm ZDDP without adding something.
> I'll try it with half a bottle ZDDP Maxx everytime I change the oil, 2 times a year. That should get my oil to a correct ZDDP level.. too much wouldn't be good and 1015ppm original is too less.
> ...


None in the garden variety oils for todays cars. Zinc was removed from "todays" oils some time ago. Specialty oils like Brad Penn, some racing oils, Shell's Rotella have the required Zinc in them.


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## Chris-Austria (Dec 23, 2010)

Oh okay, if 2oz ZDDP MAXX are enough for 5 quarts that have zero ZDDP, 1oz will be more than enough for my oil. If ZDDP will be banned from the "normal" oils here in Europe, I'll use a full bottle


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## bullet20cc (Apr 4, 2009)

*Oil*

I run 15w50 Mobile 1 and a cam addative. 67 GTO 455 550 hp. I run 6oz of cam additive. I have a two gallon oil pan.


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