Is 20W-50 best Motor Oil for 1964 Impala SS

impala
chevrolet

#1

A friend recommended that we switch to 20W-50 motor oil for our 1964 Impala SS with a 327 engine. We live in Central AZ


#2

Back in '64 10W-30 was recommended for just about all cars. Modern 10W-30 oils are much better than what was sold in '64. I’d use 10W-30 or 10W-40, but perhaps there is problem with the motor? Is it burning oil, producing blue smoke, or is there some symptom?

I’d only use a 20W-50 if the nighttime low temp is in the 60’s or above.


#3

I agree. 30w oil. Your motor is 50 yrs old. Has it ever been rebuilt? Fresh crank? Newer bearings? If you think 50w oil is required to produce ok oil pressure at idle, than you have mechanical issues.


#4

I would probably use 10W-40. If you are switching to 20W-50 in hopes of fixing an oil pressure or oil burning issue then that oil won’t help. Why did your friend suggest changing your oil weight?


#5

I recall reading stuff online about oil where it basically said that thinner oil is generally better than thicker. I’m using synthetic 0w-40 right now and plan to drop down to synthetic 0w-30 next time. My car engine seems to be in excellent shape from a wear and solidness perspective, however, even though there are 200000 miles on this 87 Nova engine. I think the previous owner used synthetic, too, and changed it pretty often.


#6

Darn trolls. An 87 nova is a Toyota clone which is a 4cyl motor. Ugh, I prefer to not recall GM cars from 87.


#7

Couple of thoughts.
I don’t think Toyota recommends 0W-40, as that is typically a European specification.
Why do you want to go thinner?
If that 64 Chevy is beginning to use oil, I’d look to some of the oils sold for “high mileage” engines, as they tend to resist burning off better than conventional oils, and often will help to keep the seals intact.
And a note for all posters: it helps greatly if you tell us how many miles are on the engines.


#8

This thread got hijacked

First we were talking about a 64 Impala. Now we’re talking about an 87 Chevy Nova


#9

20W50 is too heavy for that car. Only if you live in the tropics should you use that oil. The original spec was likely 10W30, since anything lighter in 1964 was not considered to have reliable “stay in grade” characteristics.

The best oil I would use would be a 5W40 synthetic if I lived in the Northern states and 10W40 synthetic if I lived in a warmer area. That would give good oil flow on startup and good film strength at high loads and speeds.

These engines were quite loose even when new, and a 5W20 or 0W20 would result in considerable oil consumption.


#10

One of the main reasons to go to 20w-50 in a classic car is for the zinc content. Zinc is vital for valvetrain protection in engines produced before the 70’s. It’s been eliminated in most modern oils, but 20w-50 still contains a good amount of it. You can get an oil additive to add it back in, but most parts stores don’t have it on the shelf. Google ZDDP for more info.


#11

Hey there Cavell, I’m just trying to help by giving perspective on why I thought 20w-50 might be too thick for the OP. That behavior is more like trolling than mine. It’s true that there are a lot of factors that only the owner of the 64 Impala can weigh based on the particular situation. I wasn’t saying the OP should use what I use. That is why I described my situation which is unique, like the OP’s situation is.

Tony, I want to go thinner because from what I was reading thinner tends to give better flow, and it’s the flow that’s important for engine protection rather than thickness sticking onto the parts. However, it should be true that too thin might let metal be exposed to metal-on-metal friction. It definitely depends on the wear on the engine, and that is why I mentioned my experience, because a tight engine can have good oil flow and provide best possible protection on an oil that is on the thinner side rather than the thicker side. This is largely indicated by how it has often been said that the most wear on the engine occurs at start up, before the oil begins to get flowing. A thinner oil will do that faster than a thicker oil. And since I use synthetic oil, it won’t experience viscosity breakdown, so the oil won’t thin out with use (unless gasoline, say, were getting into the oil). That is why I mentioned I use synthetic, which I recommend for engines that don’t burn or leak very much oil. On an engine that leaks or burns oil, it could get expensive to keep adding the higher-priced synthetic in order to keep the level topped off.

However, it’s possible to go too thin where the oil pressure is too low. That then wouldn’t be good. I wouldn’t recommend thinner than the oil recommended for the 64 Impala by Chevrolet, unless you have good reason. It depends on how often the engine is started up and turned off, for example, how long it is run at a time, what kind of driving is done, how much oil it leaks and burns, whether the oil is synthetic or not, and like the OP knows, how hot the environment is. Keep in mind, though, it can get pretty cold at night in a normally hot desert climate.

Edit: I was contemplating thicker oil being easier to get scraped off moving metal parts or not, and I decided I wasn’t sure because it depends partly on the how well the oil sticks to the metal. Thicker does tend to cause more drag in an engine, though, that is one reason why thinner oils have gained popularity over the years and one reason is that they tend to give a small boost in gas mileage compared to thicker oil.


#12

I get the feeling that the friend recommended the 20/50 oil based on the perception that an old car needs the added viscosity because of age and flirting with being worn out.

The 20/50 might be viable during 100 degree summers and if the driving does not involve those short 5 mile hops here and there.


#13

For that year, I’d recommend 15w40 diesel rated oil. Its more compatible with the metallurgy of that era.


#14

This might be a good idea, certainly for spring, summer, and fall in AZ. I have an '03 Ski Nautique with a 5.7 liter GM block PCM motor and that is the oil spec’d for this marine motor.