Custom Motor Build -- Conventional over Synthetic?

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ThatGuyOverThere

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Hi everyone,

I am rebuilding my motor, it's a stroker engine, V8, 5.3L and will be supercharged.

The engine builders recommend 10w40 for the break in, non-synthetic. They recommend I run 10w40 non-synthetic on regular use as well.

Is there any reason why conventional is better than synthetic here? I understand the weight of the oil is spec'd to the motor tolerances and whatnot. I just can't figure out why they recommend against synthetic oil.

With that said, which brand/line 10w40 conventional oil tends to be better for performance and protection. I don't mind changing the oil out early (3000 miles or even earlier) since the car doesn't get driven too much.

To be clear, this is a street driven car and is regularly used in the city and freeway, occasional race track use. It's driven in cold winters and hot summers as well.

Thanks!
 
They recommend it because they're clinging to the myth that an engine will "never break in" with synthetic.

I'd probably break an engine like that in with the oil they recommend so if it goes Tango Uniform they can't claim you did something "wrong," but I'd sure consider running a synthetic thereafter.
 
Thing is the motor has a one-year warranty, so I'd run the oil for at least a year before anything. I'm just wondering why they would recommend conventional for the life of the engine though--not just the break in.
 
Originally Posted By: ThatGuyOverThere
Hi everyone,

I am rebuilding my motor, it's a stroker engine, V8, 5.3L and will be supercharged.

The engine builders recommend 10w40 for the break in, non-synthetic. They recommend I run 10w40 non-synthetic on regular use as well.


Thanks!


does your engine have the hypereutectic pistons? I think those have about .001 to .0015 clearance. I don't know why they recommend a 40 weight with that type of piston clearance.

If it is under warranty, run what they say. I would run a 5w-40 (Rotella) if it actually needed a 40 weights
 
I'm not 100% sure but they should be, they are made by CP.

The builders specifically use and recommend Valvoline 10w40 conventional. They say it's what they use in their cars with the same motor.
 
Originally Posted By: ThatGuyOverThere
I'm not 100% sure but they should be, they are made by CP.

The builders specifically use and recommend Valvoline 10w40 conventional. They say it's what they use in their cars with the same motor.

Sounds like they are a little behind the times when it comes to motor oils. Valvoline 10w40 conventional is okay for a bread and butter stocker but not a Hi-Perf supercharged engine.

I'd use Shell Rotella 15w-40 for the break-in and thereafter as well, with a bottle of GM E.O.S. throw in for the intial fire up.

Better to avoid a warranty issue in the first place.
 
I talked to Marshall Engines whom I bought a reman from. They have done 250K engines so one assumes they know a little. They suggested dino oil during break-in.
 
Dino is better for ring break-in, and a high ZDDP oil would be good for a high lift flat tappet cam, but I can't think of any other reason not to use a quality syn.
 
In my engine building days,I would break all my SBC cams (20 minutes @2K rpm)in with straight 30 wt oil.After that I would drain it and run whatever I wanted,usually Castrol 10W30.If I ran synthetic oil it was M1 10W30. I have built about 35 engines.
 
im not convinced that 5.3l will even need a 40wt oil, especially if its your summer and winter street cruiser/toy. for break in id run a good conventional 5w30. after would run a 5w30 like M1 if it was mine. or perhaps something like Amsoil z-rod 10w30 if your wanting some extra zink/phos. honestly you could break it in with M1 as well, it probably will not matter at all.
 
Last edited:
Originally Posted By: Provi
Originally Posted By: Tim H.
Originally Posted By: bullwinkle
Dino is better for ring break-in


Why?


My thought is you need the friction for break-in.

http://www.mototunesa.com/break_in_secrets.htm




Sure, dino for break-in works. But if synthetic doesn't, then how are all those high-performance GM LS-series v8s and Mopar 392s breaking in, since they're filled with synthetic right on the assembly line??

Its hard to kill a myth like this, because its only a half-myth... perpetuators of the myth can always refer to the thousands of engines successfully broken in with "dino" oil (as can I- I used to break engines in with 20 minutes of Castrol GTX 10w30 before draining and switching to M1, but I did it because it was cheap, and all the assembly greases were going to do the hard work anyway!).

But I still don't think synthetic will prevent proper break-in. If it DID, then we'd see engines wearing out much faster on conventional than synth. And we don't- they may stay cleaner and last a little longer, but its not a huge difference at all.
 
Typical outdated old school thinking. If dino was essential how did my car and many others ship with synthetic?

3 generations of machinists in this family with a very successful biz that does high end hot rods all the time. Ask the old timers and they all say "no synth" in unison.

But they grudgingly admit it's a better product. The facts are it is, but the gap between ggod synthetic and good conventional is smaller than it ever was. Especially if you yank it every 3k miles.
 
Originally Posted By: 440Magnum
Originally Posted By: Provi
Originally Posted By: Tim H.
Originally Posted By: bullwinkle
Dino is better for ring break-in


Why?


My thought is you need the friction for break-in.

http://www.mototunesa.com/break_in_secrets.htm




Sure, dino for break-in works. But if synthetic doesn't, then how are all those high-performance GM LS-series v8s and Mopar 392s breaking in, since they're filled with synthetic right on the assembly line??

Its hard to kill a myth like this, because its only a half-myth... perpetuators of the myth can always refer to the thousands of engines successfully broken in with "dino" oil (as can I- I used to break engines in with 20 minutes of Castrol GTX 10w30 before draining and switching to M1, but I did it because it was cheap, and all the assembly greases were going to do the hard work anyway!).

But I still don't think synthetic will prevent proper break-in. If it DID, then we'd see engines wearing out much faster on conventional than synth. And we don't- they may stay cleaner and last a little longer, but its not a huge difference at all.

It's been 3 years since I have built an engine.If I were to build one today I would still break it in with straight 30 wt conventional oil. Then,if I wanted to use synthetic in it I would.
How do know the factory does not use conventional oil to break in an engine then install synthetic? I sure would be interested to know this.
smile.gif
 
Originally Posted By: ThatGuyOverThere
I'm not 100% sure but they should be, they are made by CP.

The builders specifically use and recommend Valvoline 10w40 conventional. They say it's what they use in their cars with the same motor.


CP doesn't make hypereutectic pistons, their stuff is forged 2618. Piston to bore clearance should be looser than for hypereutectics.
 
Factory machining is much better than the machining in even a top quality shop. The engine from the shop will have the same break in as factory engines from years ago. While we know that a so-called synthetic made with Group III base oil is actually a petroleum oil, and that if there's actually a full Group IV "true synthetic" out there, it probably won't be "too slippery" for break in, use the oil they recommend.

I'd do several low mileage oil changes with the conventional 10W-40 that they recommend, and stick with their recommendation through the warranty period for sure. By the way, the oil viscosity depends on the clearances they built into the engine, and they may have chosen slightly larger clearances than a factory engine. Anyway, they know what works in their engines.
 
Originally Posted By: BlueOvalFitter

How do know the factory does not use conventional oil to break in an engine then install synthetic? I sure would be interested to know this.
smile.gif



Why would they? The cost of filling with DINO, running for the quality assurance test, then draining and installing new synthetic would be cost prohibitive in itself. Synthetic in itself is not "slipperiest" than Dino. It is simply more robust and uniform in it molecular chain make up. This allows it to be made alittle thinner on the scale and still protect. This is where the gas mileage increase comes from, and in some cases the increased noise some users experience. Other than that synthetic will break in an engine just as we'll as an equally additive-based Dino will.
 
Originally Posted By: Tim H.
Originally Posted By: BlueOvalFitter

How do know the factory does not use conventional oil to break in an engine then install synthetic? I sure would be interested to know this.
smile.gif



Why would they? The cost of filling with DINO, running for the quality assurance test, then draining and installing new synthetic would be cost prohibitive in itself. Synthetic in itself is not "slipperiest" than Dino. It is simply more robust and uniform in it molecular chain make up. This allows it to be made alittle thinner on the scale and still protect. This is where the gas mileage increase comes from, and in some cases the increased noise some users experience. Other than that synthetic will break in an engine just as we'll as an equally additive-based Dino will.

Do you know for sure or are you speculating?
21.gif
 
Originally Posted By: BlueOvalFitter
Originally Posted By: Tim H.
Originally Posted By: BlueOvalFitter

How do know the factory does not use conventional oil to break in an engine then install synthetic? I sure would be interested to know this.
smile.gif



Why would they? The cost of filling with DINO, running for the quality assurance test, then draining and installing new synthetic would be cost prohibitive in itself. Synthetic in itself is not "slipperiest" than Dino. It is simply more robust and uniform in it molecular chain make up. This allows it to be made alittle thinner on the scale and still protect. This is where the gas mileage increase comes from, and in some cases the increased noise some users experience. Other than that synthetic will break in an engine just as we'll as an equally additive-based Dino will.

Do you know for sure or are you speculating?
21.gif




Makes sense to me what Tim said.
 
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