Recommended summer oil for a 1965 GTO - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 04-10-2019, 09:25 PM Thread Starter
 
HickBoy's Avatar
 
Join Date: Aug 2018
Location: Los Angeles, CA
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Recommended summer oil for a 1965 GTO

As it's getting closer to summer I am wanting to swap out my engine oil. The car is a 1965 GTO but I am not 100% sure the engine is original but I believe it's mostly stock (Screenshots attached). Currently the car runs fine but when it's cold my oil pressure will hover around 60psi regardless of whether I am at idle or driving 70mph on the freeway. If I go beyond 70+ it jumps up to 70psi. Once the car warms up it starts to drop back to around 30psi at idle and then increases about 10psi for every 10mph faster I go.

It can take a good 30+ minutes of driving before I see the change where the pressure starts to follow my speeding up or slowing down.
I'm also not sure that it's old school oil with Zinc as I had a shop replace the valley pan and they did an oil change with whatever shop oil they use but I am guessing 5W30 (without zinc).

I live in the San Fernando valley (Los Angeles) here in California so during the summer it can be 100deg+ on warm days and almost never drops below freezing. I believe the engine has flat-tappet cams so I am thinking I need a good oil with Zinc. What do you recommend I put in for the summer?

Engine Block Code Front: 530660 WA
Engine Block Code Back: 9778789
Intake Manifold Code: 9778816
Valve Code: 8775
Attached Thumbnails
Click image for larger version

Name:	CowelTag.jpg
Views:	37
Size:	58.9 KB
ID:	118425   Click image for larger version

Name:	BlockCodeFront.jpg
Views:	34
Size:	72.8 KB
ID:	118427   Click image for larger version

Name:	BlockCodeBack.jpg
Views:	27
Size:	50.6 KB
ID:	118429   Click image for larger version

Name:	Intake.jpg
Views:	35
Size:	175.2 KB
ID:	118431   Click image for larger version

Name:	ValveCode.jpg
Views:	37
Size:	295.0 KB
ID:	118433  

Click image for larger version

Name:	EngineTop.jpg
Views:	40
Size:	262.2 KB
ID:	118435  
HickBoy is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 04-11-2019, 08:38 AM
 
Join Date: Jul 2016
Location: North Louisiana
Posts: 624
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Everybody has their own idea about oil.

I live in Louisiana, which can also get hot in the summer. Don't have a street Pontiac, right now. I have Rotella T4 15w-40 in my 455 bracket engine. It supposedly still has a 1200 level of ZDDP in it. I use it because it's quite a bit cheaper than the HP brand oils, & they always have plenty at my local Wal Mart.

When I take it to the track this summer, I'll probably also add a bottle of STP oil treatment. It makes the oil a little thicker & also adds a slight amount of ZDDP.

https://www.walmart.com/ip/STP-Oil-T...xoCYCwQAvD_BwE

Back in the old days, I ran 50w Vavoline racing oil, plus a can of STP. I've always experienced the same as you, having high oil pressure, 'til the oil gets hot. That's just a fact of life. Oil is thicker when cold & thinner when hot.
bigD is online now  
post #3 of 4 (permalink) Old 04-11-2019, 01:41 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,558
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 119 Post(s)
I'm in hot Fresno CA, and run Rotella 15/40 in my old flat tappet cars. Have for years. Never any issues.
geeteeohguy is offline  
 
post #4 of 4 (permalink) Old 04-17-2019, 11:42 PM
 
Join Date: Aug 2014
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I agree, everyone does have their own idea about oil. You should be fine with any name brand oil that advertises high zinc (zddp) content. Either synthetic or dino oil. I like Amsoil Z-Rod which is designed for older cars. I strongly recommend not to add STP oil treatment or any other oil additives, they just aren’t necessary if you use a good quality oil to begin with. Here’s why, years ago I was adding STP to my Road Runner simply because my engine was tired and I fell for their claims. I was planning a rebuild and figured it would by me some time. About a year and two or three oil changes later and I decided to do the rebuild. When we disassembled the engine at my friends shop (who built race engines for a living) he immediately reprimanded me for using STP oil treatment. I was shocked and asked how he knew I was using it, then he proceeded to point out this gray clay like build up in the corners and galleys throughout the block and heads. Apparently it’s most common reaction is to turn into this gray substance that separates out of the oil and settles into all available corners. He told me it was a waste of money and never use it again. Imagine what could happen over time as this stuff builds up, especially to modern engines that tend to have tighter tolerances and smaller oil return passages.
brianz426 is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
which oil is recommended in a muncie 4 speed Mr.409 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions. 8 12-02-2018 08:14 AM
original recommended oil viscosity for '70 400CI V8? doubleDizz 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 2 08-09-2013 03:16 PM
Pennzoil Ultra - The only motor oil exclusively recommended by Ferrari North America. batmans Service, Maintenance and Technical Discussion 5 03-29-2012 04:55 PM
Ideal offset for recommended fitment BlackPearl Wheels and tires 2 09-13-2006 10:20 AM
So. Cal: Recommended Shops for GTO blue04gto Pacific 9 04-20-2006 04:06 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome