# 66 LeMans - Oil ?? (I know)



## LeMansChaser (Mar 13, 2012)

So I searched and read quite a few posts before placing this post (I'm trying not to waste anyone's time). With that said I have a ORG 326 w/ 71K miles in my 66 LeMans (4th owner). What kind of oil should I put in it? 

I reached out the previous owner and he said on his last oil change he put in 10W-30 Synthetic Blend. From what I have read in previous posts I'm thinking I should use something else, but what? PS. I do have what appears to be a rear mail oil seal leak. (Yes, I do want to replace it but everything with time)

I read everything from 10W-30, 10W-40, and 20W50, some Synthetic some conventional, some adding a Zinc additive such as ZDDP or ZDDPlus. The bottom line is I have no idea what I "should" put in this bad boy. 

As always, thanks


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## 68greengoat (Sep 15, 2005)

And don't forget some of us who use Rotella 15w-40 diesel oil. As you found, there is really no one answer. It comes down to personal preference. Some will say mineral oil only, others have no problem with synthetic. I think everyone agrees with a zinc additive like ZDDP.


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## leeklm (Mar 11, 2012)

Yep, what he said... I run synthetic in my everyday cars, mainly for extended oil changes and cold weather startup. I would personally stay away from Syn on an older/tired engine, simply because it WILL leak and burn more oil. I do not operate a fleet or anything like that, but have used most every oil and additive out there in my 35 years of driving many miles (including 10yrs of circle track), and have never had a single oil related problem.


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## geeteeohguy (Feb 2, 2008)

In your 326 I would probably run the Rotella 15/40 with a ZDDP additive.


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## 68greengoat (Sep 15, 2005)

^^^^ Another Rotella user, actually GTOguy put me on to it. Thicker oil equals less leaking. 20w-50 is getting a little thick.

Try using this stuff to "help" slow down the rear main:
Rear Main Seal Repair (p/n 1050) | Products | Bar's Products - Premium Automotive Chemicals


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## 05GTO (Oct 6, 2004)

68greengoat said:


> And don't forget some of us who use Rotella 15w-40 diesel oil. As you found, there is really no one answer. It comes down to personal preference. Some will say mineral oil only, others have no problem with synthetic. I think everyone agrees with a zinc additive like ZDDP.


:agree

Shell's Rotella T6 has 1260ppm of zinc in their oil, 

Some of Mobil 1 Synthetic oils also have high levels of zinc,


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## 1968 Q8 (Jun 9, 2011)

I use Joe Gibbs Conventional HR-1 15w50 oil. It has a high zinc content, and is designed for older, original engines with greater/worn clearences and flat tappet cams. Not trying to persuade you on it, just letting you know what I use in mine. I've got 63,000 orig. miles on my 400. Has a few leaks here/there so i go a little thicker on the oil, the Joe Gibbs has done me well so far 

Also keep in mind, some synthetics have detergents in them that may clean out points of leakage and may increase oil loss


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## 1968 Q8 (Jun 9, 2011)

68greengoat said:


> ^^^^ Another Rotella user, actually GTOguy put me on to it. Thicker oil equals less leaking. 20w-50 is getting a little thick.
> 
> Try using this stuff to "help" slow down the rear main:
> Rear Main Seal Repair (p/n 1050) | Products | Bar's Products - Premium Automotive Chemicals


Hey Green,

Any experience with that product? I'm getting sick of cleaning the drips on the driveway everytime I go out!


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## 68greengoat (Sep 15, 2005)

I've only used 1 quart, so, I really can't give a thumbs up or down. It "seemed" to slow it down. It didn't totally get rid of the leak. How bad your seal is leaking will make a difference. GTO Judge used the stuff too, maybe he'll weigh in with his results.

I park mine in the garage all the time. I also keep cardboard handy. I change it out when needed. Bottom line, the only way to really fix the leak is to change the seal.... From what I've heard, Viton makes a good one....


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## 1968 Q8 (Jun 9, 2011)

I agree, doing it properly is the best way, thanks for the reply


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## jetstang (Nov 5, 2008)

Easier to swap the cardboard than rear main. I would try the instant fix stuff first, big job to do the rear main..20W50 is livable in the south, but up north will cause hard crank conditions in lower temps. Synthetic oil atoms are smaller than conventional and will find leaks that conventional oil won't. Change the oil more often and you don't need synthetic. I use the diesel oil, but not all have ZDDP, but are still better than most oils.


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## LeMansChaser (Mar 13, 2012)

Thanks All. I like the 15w-40 option with ZDDP, seems like a good middle of the road option. I was talking to a buddy who said the BG RF-7 is a great additive that helps fix leaks. A year or so back he worked at a Grease Monkey and he swears by it. 

Thanks again! Everyone is always really helpful and the feedback is GREAT. 


Sent from my Autoguide iPhone app


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## Chris-Austria (Dec 23, 2010)

I also searched for the "best" oil to put in my Pontiac (428).. now I use 15w40 with ZDDP and it works great


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