About oil wt choice?

[coolman]

(In synthetic oils only)Would there be any benefit or harm

useing a 10-40wt instead of a 5-30wt or 10-30 in a small block chevy lo5 5.7l. 50,000 mile on engine. The first 47,000 was (prior owner) a short trip,very low mileage, rarely change to oil driver.

Ps, Engine is in good running condition.

 

[jorton]

There would be no benefit bnecause the engine is low mileage. There would be no harm because fresh oil is good for engines. Combustion chambers and rings may be dirty. Use Shell Rotella synthetic 5w-40 oil and Gumout Regane in the gas.

 

[williar]

I'd stick with the 5w30 that the manufacturer recommends. Under normal usage, going to a heavier weight may cause sludging, poorer performance, and worse fuel economy.

 

[Throckmorton]

I never knew that synthetic oils could cause sludge. Without proof I'd be skeptical of that idea.

Synthetic 10-30 might be a better choice if you're going to do a lot of towing or subject the engine to unusually high loads. Otherwise I'd assume that 5-30 should suffice. But I am a n00b, and don't claim to have any special expertise on the subject. :2cents:

 

[Bryanccfshr]

Synthetic oil is not immune to sludge. Sludge is usually a mechanical and design issue.

 

[Ray H]

Quote:

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I never knew that synthetic oils could cause sludge.

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I'm not comfortable with the wording that any motor oil formulation will cause sludge, but all are subject to sludging if abused sufficiently. A synthetic will resist sludging far longer than a conventional formula, but will do so if over-heated routinely and/or driven to ridiculously over-extended oil change intervals. You only buy some extra time with a full synthetic. Miracles are not part of the bargain.

 

[Throckmorton]

If overheating was what created sludge then wouldn't a synthetic 10-30 provide better protection than a 5-30?

 

[KW]

I would agree in most cases because 10W30 has fewer polymers than 5W30. But this might not alway be the case.

10W40 will not harm your 350. If you aren't going to be working the motor hard one of the 30 weights might be a better choice for fuel economy.

 

[JeepCreep]

coolman, the 10w-40 won't really hurt a bit. I would only use it during the summer here though. Since you know what I mean when I say mild winter, I would say a 5w-xx isn't really necessary. It's over 75 degrees here today.

 

[Mitch Alsup]

I would recommend sticking with the 5W-30 oils recommended by the manufacture. I don't remember if the Lo5 is an LS1 derived engine (I suspect it is). The LS based engines are know to like thini oils and several of the oil galleys are smaller so a thicker oil may not flow as well , expeciall early after a cold startup.

In fact, I might be persuaded to try a 5W-20 oil for this engine, unless you are considering track usage senaios.

 

[AEHaas]

I second the use of a 5W-20. These all perform equally as a 30 wt. oil. If you are doing mostly short trips of less than 20 or 30 minutes long then the 20 wt. oils will be superior because they would minimize start up wear during the drive.

aehaas

 

[dave1251]

Quote:

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I would recommend sticking with the 5W-30 oils recommended by the manufacture. I don't remember if the Lo5 is an LS1 derived engine (I suspect it is). The LS based engines are know to like thini oils and several of the oil galleys are smaller so a thicker oil may not flow as well , expeciall early after a cold startup.

In fact, I might be persuaded to try a 5W-20 oil for this engine, unless you are considering track usage senaios.

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Mitch I thought that LS family likes an thicker oil? Like GC.