How does an engine builder determine oil type?

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So Im on an overnight shift here at work and got to thinking... How does someone building a custom engine determine what type of oil to use? How do they analyze metal compositions used in different parts to make their determination? Or is it more based on application? Induction system? Every time I see the "power block" on spike tv, they build a new engine, dump some royal purple 5w30 in it, and call it a day grin
 
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Even the manufacturers don't fully understand all the interrelationships between engines and oil. Best they can do is test a bunch of engines with different types of oils and viscosities and see what happens. Engine builders go on past experience. If they start getting a lot of returns from folks using a certain type of oil, they will change their recommendation to something different.
 
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Main and connecting rod bearing clearances are typically .002-.0025". That has not changed in the last 50 years. What has changed, is the events that reduce those clearances during operation. Here is a short list of those events; Engine block(case) flexing. Crankshaft flexing. Crankshaft harmonics. Ignition detonation. High rpm with a heavy rod and piston (bob weight) combination. Large main and rod journals, and piston pin diameter. The last item on the above list is more complicated than simply smaller journals equal lower bearing surface speeds. The engine design features that allow for a less viscous engine oil than in the past not on the above list is; Larger sump capacities. Engine oil coolers. Better bearing materials and journal finishes. Higher quality fasteners. Better metals, composites, and gaskets. Higher volume oil pumps and engine design that puts the oil where it is needed. Better ignition systems and fuel injection that help reduce engine oil dilution from fuel. Roller valve-train. The minimum HTHS of SAE 20 is higher than it was 20 years ago.
 
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Had a friend with a hot rod that he had "built loose" and ran M1 15w50 in it. Assume it was bearing clearances.
 
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Experienced "hot-rod" engine builders allow for all the pit-falls that are contained in my above list, and then some. They have learned the hard way that building engines to minimum specified clearances is asking for trouble. A short run of failed engine returns will put a shop out of business in short order. Forged pistons, mechanical lifters and roller timing chains to name a few, all add to the calamity. The 15W50 engine oil (a modern day 20W50) whether needed or not, along with a blocked-off oil filter bi-pass completes the artist's interpretation.
 
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Originally Posted By: Guitarmageddon
So Im on an overnight shift here at work and got to thinking... How does someone building a custom engine determine what type of oil to use? How do they analyze metal compositions used in different parts to make their determination? Or is it more based on application? Induction system? Every time I see the "power block" on spike tv, they build a new engine, dump some royal purple 5w30 in it, and call it a day grin
My BIL is a third generation machinist who works with a very upscale clientele. Lots of older rodders who bring him tons of expensive machinery. Recently a gentleman brought him a 20k crate motor and orderd tens of thousands MORE machine work done on it. They also buy and rebuild old equipment routinely from all over the country. They are extremely "old school" and my BIL still has his Dad there working, too. Their oil is Castrol GTX. It's just what they like, period. No synthetics used or even recommended. Short intervals, high viscosities are the norm...
 
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We rebuild engines but we rebuild them totally stock and we tell our customers to use whats in the manual or on the oil cap. It has worked for us for over 30 years. We do very little custom work but we are one of the larger rebuilders of stock engines in our area. It seems that in our field the average engine guy has the thinking that oil is oil.
 
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I'd bet that most custom builders base their oil recommendations on there being nothing wrong with going a little thicker. Thicker is generally safer if you're not sure how thin a grade would provide adequate oil pressure as the engine will be used. Brand really doesn't matter much, although any synthetic is also a safer choice if you're not sure how hot the oil might get at any given point.
 
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I agree with SteveSRT8, fdcg27, AND crazyoildude. A stock rebuild...the cap/manual makes sense. A person who is spending $40k on an engine isn't going to be worried about the 2% fuel economy that may be saved by exploring the thin end of the spectrum....engine builder's reputation is best served by being safely thick.
 
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Originally Posted By: Guitarmageddon
Every time I see the "power block" on spike tv, they build a new engine, dump some royal purple 5w30 in it, and call it a day
That's one reason I hate that show. I feel like I am watching a 30 minute commercial for a handful of products. Adam Carolla's CARCAST podcast had some information about this topic. It was the Joe Gibbs oil episode.
 

CT8

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Originally Posted By: FL_Rob
Those shows are parts commercials,period.
Yep most people don't have clue. I really despise most all TV programs.
 
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