...I know this next question has been discussed to exhaustion over the past, but what weight of oil is suggested for a stock C4 engine with about 70,000 miles on it? Full Synthetic, Synthetic blend, or all natural dinosaur oil? I'll be driving my future Vette in fairly mild southern CA weather; no freezing temps, and no burning hot days over 98 degrees. Without any previous Vette engine knowledge, I'd guess synthetic blend; 10-40 or 20-40 weight? Please verbally abuse me if I'm wrong here

 

5w-30 full synthetic

 

Hmmmm, ok...let this discussion continue...

 

There is nothing more to discuss. You have been given the correct answer.

 

thats what the mfr recommends....tried them all and use cheap store brand dino oil and a good filter-felt like i was throwing money down the drain epecially with an old motor. If its going to go the type of oil wont change a thing.

 

I've always believed that no matter what brand or type (full synthetic or regular dino oil) one uses, it's the oil change interval that is crucial. Just cause the oil manufacturer may state their oil can go 7k to 10k miles between changes, means nothing. There's a lot of discussion about synthetic oils too, but let's narrow down the oil weight question I have. What is the best weight to use in a mild driving environment in southern urban CA? 5w-30w seems too light to me since I don't encounter real cold weather.

 

5w-30 isn't too thin for your car. I've ran 0w-20 in my '86 at the dragstrip in summer in Texas. Idle oil pressure was about 10psi and nothing broke. I replaced the cam & heads since then, no noticeable wear on the cam or lifters. Fill in your profile so we know what you're asking about.

 

Hello there,

Your engine was designed by some fairly bright people in Detroit and when they design an engine, they get to really "understand" the engine and its particular needs. The Engineer who designed this engine designed it with fairly tight tolerances. The tighter tolerances require a thinner oil to get in between the surfaces so it can lubricate the parts.

The second poster told you what the GM people have said to use for these cars. I would follow their advice as it is the "correct advice".

Almost all new engines are built with such tight tolerances that the old style oils cannot properly get into the spaces provided for the lubricant to flow. We have a new 2018 VW and it requires 0w-15 oil. They said it should be 10,000 miles before the first oil change. These new engines are being designed for efficiency and longevity. I just don't agree with going 10,000 miles on the original oil. I use the proper oil and I changed it twice and I don't even have 5,000 miles on it.

I have 2 Corvettes, a factory stock 1988 Coupe and a 1968 L-71 convertible 427 with a four speed. This 427 was custom built and it does not have the tight tolerances like the newer cars do. In the HOT summer time weather I use a slightly thicker oil but the rest of the time it uses 10w-30. Running a very high compression makes a lot of extra heat so the oil wears out faster.

I do use good quality oil in my Corvettes. Both get full synthetic and they both get their oil changed at least once every 12 months. I was taught that oil turns acidic and will damage parts if it has been left in an engine too long. I have changed the oil on a car even though I never drove it that year, I will not leave oil in anything that has a gasoline engine for more than twelve months.

The other thing that is really important to remember is that they have taken the Zinc out of conventional motor oil. If you have an older engine be sure to add Zinc to the engine or you risk destroying your camshaft. You can find specialty oils that have the zinc in them but they can be expensive.

Do as the manufacturer tells you and your Corvette will live happily for many years! Good Luck

 

5w30, 10w30 if it is only driven in warm weather. Synthetic, semi or dino doesn't make a damn difference if you're putting a few hundred miles on it a year. The LT engines came factory with mobil 1 iirc so use that if it makes you feel good. 350s don't really care what you throw in them. Change it once a year or if you actually drive it enough to hit a mileage interval change it then.

The difference between good conventional and synthetic is marginal until you start pushing out intervals. The beauty of synthetic is it remains stable longer. 3000 miles with synthetic is a waste imo.

 

if you check your owners manual it should tell you 5W-30, 10W-30 if you dont run in cold weather, Lt's I believe they recommend synthetic or at least thats what they came with from the factory.

 

This is correct. Changes are more important than brand/type. Especially since todays oils are all better than good enough.

Quote:

Originally Posted by RetroGuy

What is the best weight to use in a mild driving environment in southern urban CA? 5w-30w seems too light to me since I don't encounter real cold weather.

The folks above have already answered this for you. Several times. They said 10w30.

 

Let the discussion continue....

 

...This is why I registered for this forum; great Corvette knowledge and advice. THANKS Everyone!