I have a 1986 base and the owners manual says to use SAE 30 for operating temperatures of 40 - 100 degrees. Which is heavy duty . Ive been using 5W 30. Can anybody give me some feedback on this?

This is from my GM 1986 corvette owner's manual

 

5w30 or 10w30 is perfectly fine for the engine. Don't use straight 30 weight.

 

An oil thread. This could go sideways or nowhere.... At least you didn't what the best oil is.

 

why does it say in the GM manual for my 1986 Corvette to use S.A. 30 oil for operating temperature 40° and above

 

it's my understanding that chev added hydraulic rollers to the L98 in 1987. in my '86 C4 with an early L98 engine, I use an oil with additives for flat tappet engines.

 

Well the 30 is for its viscosity at 100 Celsius, so as long as you are using that you are following the spec. The engine gets to those temps very fast. 5w or 10w is the cold spec, which is thinner and what you want on starts.

Straight 30 would not be your friend in cold weather starts, and would normally only be used when in old engines the gaps are bigger than your thumb.

As to why its in a 40 year old manual, I don't know, just don't use straight 30.

 

Correct a Zinc (ZDDP) additive is good to add to flat tappet L98s (85-86) for long term use. Modern oils have less zinc.

 

lets see a screen shot of that

 

If one is worried about the lifters walmart usually has Valvoline VR1 10w30 pretty cheap. Silver bottle, conventional, not the low detergent race stuff.
There's always something better to be had but the VR1 is decent and cheap, 5 or 10w30 is fine unless it's worn out an the oil pressure sucks.
The stock valve spring pressures are pretty mild, especially with age.

 

The valvoline VR1 is a conventional oil, non synthetic, hood got flat tappet cams and for racing

 

I will be the first to say it. I don't believe the owners manual really calls for straight 30 weight. Hell, 40 years ago thats what you used in a lawnmower and even lawnmowers call for something like 10w-30 oil now. Dan

 

 

5w30 preferred, think it says that on the oil cap too. Even at 150K mine was fine with it. Have 10/30 VR1 in it now mostly because it was cheaper lol...

 

 

What it says is that "5W-30 is preferred". Note that the 5W-30 arrow is the only viscosity with the arrow pointing downward. They allow the other viscosities at the indicated minimum temperature or higher. They do not say to use the thicker viscosities. Only that they are allowed at the minimum or higher temperatures indicated.

I live in Southern California. Temperature at start up is <40F about 5 days a year. I ran straight 30 in my 85, my 4.3 S-series DD's, and probably the boat's 327 as well for a couple of decades. I liked the higher hot oil pressure and the engines ran quieter. The primary reason I stopped was that 30 is difficult to find except as a Compression Ignition (diesel) oil which has zinc and phosphorus levels that are harmful to cat converter health, which being in California is also a concern as cats need to be functional to pass biennial emissions.

I've never run 5W-30 in any of my cars even though that has been "preferred" since 1986. Reason being that the rod bearings in my bought-new 1993 S-10 Blazer looked like crap at 103k miles. I had been running 10W-30 (not the recommended 5W-30) and the rod bearings still had significant wear for the mileage. That engine used Delo 400 30W for the next 300k miles, the guy I sold it to never had the heads off either, and ran it to over 400k miles before the rust worms got it. Yes, he lived in Michigan, and still ran 30W because he didn't want to mess with what had worked for 20 years.

The "correct" viscosity is dependent on operating conditions and the specific characteristics of the engine the oil is in. I have 7 cars and the boat. They all use a different viscosity and brand oil. (One of the cars uses a specialty 10W-60 that solves a lifter issue unique to this particular engine.) Royal PITA, but I strive to use the appropriate oil for the conditions and engine. I don't have bearing or other trouble, and consumption is tolerable.

If the OP seldom starts his engine at <40F, he'd be fine with straight 30. If he can find it, he'll have higher hot-oil pressure at idle, and engine operation, particularly when cold, will be quieter.

 

The cold start wear, cold being a cold motor not even cold ambient, has been well documented for decades as a reason for multi viscosity oil. Run what makes you feel good but there's no scientific reason to run straight 30 or such unless one is in the Arab desert or such. The parasitic drag alone from heavy oil is a downer and I wouldn't willingly subject and engine to that without good reason myself. People have been putting hundred of thousands of miles on all manner of engines with 5 or 10 30 for decades now. Wear is just not an issue due to viscosity. There's some argument to be made against reeealy light oils that manufacturers were suggesting to meet cafe and such but that's sort of a case by case deal. My LT1 has 250k on it with 5w30 for example, it's fine. So is the ole L98 unless it's half wore out. My un remarkable 156k 86 has 60 cold (like summer cold) and about 15-18 hot idle when it's 90+ out, 45 or so at cruise. Perfectly boringly normal. As a general rule of thumb if an engine can't build and maintain acceptable oil pressure with what the factory said to put in it something is wrong. That dosent mean it's end of life, but there's wear. 5 or 10w30 is perfectly fine for a healthy 350 Chevy at just about any half way normal climate and it's a more effecient and less wear enducing than a straight heavy weight. Unless it's 120 degrees in the shade, you're holding high rpm constantly, or there are excessive clearances in the engine. Check out Bob is the oil guys forums, those oil nerds (bless em) are usually pretty on top of things. You can also run a uoa and usually see the excess wear from the thicker oil not lubricating as quickly on startup vs a lighter one. This stuff has all been sorted out decades ago.