Oil question for stock 350

[Michel73]

I'm almost sure this has been asked before but if it has I missed it :duh I have a 30 year old stock 350 - should I use conventional or synthetic oil :confused Any help is much appreciated


Michel

 

[Vader]

How long do you want it to last?

 

[SwaveDave]

Ive read more technical articles on this subject, than ive had hot dinners ! Full Synthetic oil is the way to go once an engine is broken in.

 

[billybob]

SwaveDave,

I would agree with a newly broke in engine, but not en engine that was broke in 20+ years ago.

Synth will cause the seals to leak while pure dino wont. If you've been running dino stick with it, change every 3k and no worries. If you plan on rebuilding use dino for break in then switch to synth.

Bill

 

[Jack]

I'm sure there'll be plenty of disagreement ... but here goes.

I agree that synthetic's probably best ... once a motor is broke in w/ dino oil ... BUT only on a motor that's relatively fresh/recently built-rebuilt.

Old gaskets & seals "take a set." Synthetic flows a little easier than dino. Synthetic will tend to flow through old gaskets' pores and around old gasket's and seal's surfaces ... it'll probably leak.

I put synthetic in my old vette's old hi-mileage 350 when I got it ... it leaked like crazy ... went back to dino and it leaked only a little. On the other hand, I upgraded to synthetic in a 25K mile cutlass and I never had a problem.

As I see it, the major benefit synthetic offers a performance "street car" (emphasis street) is that moving parts wear less and last longer. Well ... if you've got an old, hi-mileage motor ... then you've already got a lot of the goody out of its wear surfaces ... synthetic'd be a hi-dollar tinkle in the breeze. If it's old/hi-mileage ... I'd suggest simply maintaining it with a good brand of dino oil ... 10W-40 in moderate climes ... 20W-50 when it's hot.
JACK:gap

 

[SwaveDave]

Amsoil has some good tech articles on the subject at www.amsoil.com .

 

[Tom73]

Michel,
I run Mobil 1 10w30 in my '73 LS4. Want to give it all the advantages that I can.

tom...

 

[Mike Carter]

I run straight 30W Castrol in mine, always change by time and or mileage (3 months/3000 miles), I had erratic oil pressure indications with lighter weights.

Mike

 

[mapman]

New Corvettes come with 5W-30 Mobile 1 from the factory. There is no "break-in" oil. They run fine on the synthetic from the beginning.

These engines (LS1/LS6) have much tighter manufacturing tolerances and require the lighter 5W-30 synthetic oils. Heavier oils do not lubricate these engines well and can result in engine damage. (Loss of HP and increased temperatures also result when heavier weight oil is used.)

On a 30 year old car, I would continue to use the oil recommended in your user manual. For my 1980 it is 10W-30 (dino). If a heavier weight oil is "required", I think you are just masking engine problems that need to be addressed.

On a rebuilt engine I would also use the original spec oil. Mobile 1 is great oil (I use it in my 2003 Corvette and my 2002 Chevy pick-up) but it is also expensive. The newer cars come with sophisticated computer monitoring that tells you the remaining oil life, this allows you to get your money's worth out of the expensive synthetic oil. Changing Mobile 1 every 3000 miles, would just be a waste of money. Keeping Mobile 1 in the engine longer than 3000 miles, would just be a shot in the dark (unless you have oil samples drawn for analysis).