Oil and transmission fluid

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DeadHorse
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Joined: Thu Jan 26, 2017 6:16 pm

Oil and transmission fluid

Post by DeadHorse »

I am wanting to change out the oil and transmission fluid in my 1966 Monza with HG trans. My understanding is that not just any oil or transmission fluid can be used. What types of fluids do I need and any direction on where to find them?
Mike


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66vairguy
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Joined: Tue Dec 21, 2010 3:44 pm

Re: Oil and transmission fluid

Post by 66vairguy »

Not sure what a "HG" transmission is.

If you mean you have an automatic transmission, or a Powerglide (PG) then the differential can use any modern gear lube, or a GL5. The Powerglide used a Dexron fluid, that now has been superseded by Dexron VI. Supposedly you can use Dexron VI in older transmission. There is also a fluid called DEX/MERC. This fluid is not approved by GM for their transmissions, but MIGHT work in a 60's Powerglide. You'll have to ask around, do research.

If you have a MANUAL transmission then you are limited to ONLY a GL4 lubricant because the transmission and differential share lubricant. NO GL4-5, NO GL5. Of course there area a lot of aftermarket "boutique" oil companies that long on claims and short on facts selling modified GL5 lubricants that will work in a manual transmission.

Changing the lubricants is always a good idea. A fellow who does most of the transmission/differential work on the west coast says the number one reason for failures is folks DO NOT change the lubricant.
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DeadHorse
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Re: Oil and transmission fluid

Post by DeadHorse »

Thanks. And yes I meant PG. that was a wealth of knowledge. What about for the engine? I have heard the newer oils are not good to put in them. Is that true?


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66vairguy
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Re: Oil and transmission fluid

Post by 66vairguy »

DeadHorse wrote: Mon May 01, 2017 7:45 am Thanks. And yes I meant PG. that was a wealth of knowledge. What about for the engine? I have heard the newer oils are not good to put in them. Is that true?
There seems to be as many opinions on motor oil for a Corvair as there are owners. If you are driving in a climate were the car won't be operated in temperatures below freezing or above 90F, then you will use a 10W30 that GM specified. There is an endless argument about new oils and low ZDP (or ZDDP). ZDP was increased in the 60's, then reduced when catalytic converters came out. Some think the new low ZDP oil will RUIN an engine by causing a camshaft failure. Well here's a surprise - I spent a year asking all the Corvair owners I ran into if they were using the low ZDP 10W30 oils for more than a few years. Those that did said they had NO issues with the camshaft or lifters - NONE. So I went online and found some excerpts from the old SAE papers. I found that in the early 60's the BIG THREE decided to extend motor oil change intervals from about 2,000 miles to about 6,000 miles as a way of advertising LOWER maintenance costs. Within the first year camshaft failures under warranty went up. Note that new flat tappet camshaft failure has always happened, but usually is a minor issue. The increase in the number of expensive warranty fixes prompted an investigation and the oil manufactures made improvements in the motor oil to make it work on extended oil changes. One of the fixes was to increase the amount of ZDP. They also found TOO MUCH ZDP also caused engine damage!!

Today motor oils do have lower ZDP, but overall the motor oils are superior to what was produced in the 60's. WHAT TO DO. It's really simple - just change the motor oil every 2,000 miles, or at least once a year. ZDP is primarily meant to protect the camshaft lobes when the oil film shears as in when the oil is worn out due to extended mileage.

There are a lot of "aftermarket" motor oils with greater ZDP, seal swelling chemicals, etc. meant to help old engines. The experiences with these are mixed. There are also "boutique" oil brands like Amsoil and others who make great claims. There is a lubricant fellow - richard1 on the other forum - who says he has trouble getting any hard data from companies like Amsoil so it's difficult to verify their claims.

A lot of folks went to Shell Rotella diesel motor oil years ago - BUT Rotella was revised to reduce ZDP when the clean diesel rules came into play and they now make several types and ONLY one is rated for gasoline engines and only comes in 5W30 (too thin for a Corvair engine). The 10W30 Rotella is NOT rated for gasoline engines. Some folks have recently reported camshaft issues in Corvairs using the 5W30 Rotella - so I would avoid it even when you hear folks still claim it works.

WHAT TO DO??? If you have a healthy Corvair engine driven in normal conditions (no racing) then I can only say that I've had no issues using a good name brand 10W30 motor oil and changing it every 2,000 miles.
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