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I have a buddy who is rebuilding an LM7 to swap into his 87 El Camino. He isn't a member on here, but he wanted to ask if he can use synthetic oil to break it in. I asked if there was a specific oil he wanted to use and he said "Royal Purple, and whatever is closest to the stock weight. But they have a break in oil too that I wanted use if I can."
That's all of the information I have at the moment, if you need more let me know and I'll ask.
If he is replacing the rings or honing the cylinders at all he needs to run a break in oil with a higher zinc content so that the rings can seat properly.
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Just think there are thousands of vehicles of all manufacturers produced every year that leave the factory with synthetic oil. And most of those vehicles are the higher performance models of those manufacturers.
Why don't you just tell him to run the royal purple break in oil. Then switch to whatever he wants after that. Just be sure to cut open the filter after the break in is done and check it for debris.
Just think there are thousands of vehicles of all manufacturers produced every year that leave the factory with synthetic oil. And most of those vehicles are the higher performance models of those manufacturers.
They have zinc additives in the first run of oil. If you run synthetic, the rings won't seat and you will lose the crosshatch pattern on the cylinder wall. That's how new/fresh rebuilt engines get ruined.
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I never run synthetic break in or not. I run mineral oil designed to haul 80,000+ lb loads behind 10+litre 800+hp/2000ft/lb turbo motors and live doing it. That german brand that reads like ***** but with a H. My engines have never been happier.
I also never run synthetic in anything. I'm my race engines I run Valvoline Racing oil. It has zinc in it. In my high mileage and road race engines I run 15w40 diesel oil.
New GM crate engine instructions say to use any oil that meet GM4718M standard. Doesn't say anything about adding zinc. The instructions specifically say to use Mobil 1 as it meets that standard. The instructions go on to say other synthetics may meet that standard but not all synthetics will meet it. But what the hell do GM engineers know. Here are some oils that meet that standard according to Bob is the Oil Guy.
As some that has seen a new motor blow up during break in using synthetic oil i would stick with some break in oil. For the little bit of cost why would you even want to take the chance.
New GM crate engine instructions say to use any oil that meet GM4718M standard. Doesn't say anything about adding zinc. The instructions specifically say to use Mobil 1 as it meets that standard. The instructions go on to say other synthetics may meet that standard but not all synthetics will meet it. But what the hell do GM engineers know. Here are some oils that meet that standard according to Bob is the Oil Guy.
But thats not for break in. The factory has already used break in oil and changed it before it goes out for sale.
I dont like synthetics for what was mentioned above. In a race engine, the heat can get too high which causes a synthetic oil to break down. Standard oils are actually better for high temps.
Use a 30 weight break-in oil and go through the procedure to properly seat the rings. After a bit, change the oil and use a good oil based on your engine's tolerances. If it is built to factory spec, then use a good 5w-30. If the engine is a little loose, then maybe step up to a 5w-40.
There is nothing wrong with using synthetic, and despite tests proving time and time again that it is vastly superior to dino oil in every aspect, the old wives tales and fear mongering still persists. I use Amsoil without fail, for both break-in and regular intervals.
But thats not for break in. The factory has already used break in oil and changed it before it goes out for sale.
I dont like synthetics for what was mentioned above. In a race engine, the heat can get too high which causes a synthetic oil to break down. Standard oils are actually better for high temps.
I run Rotella synthetic 5w40 in everything I own. My Camaro without an oil cooler saw 315 degree oil temps 4 times for 20 minutes at a time of the track day. I sent the oil in to be sampled at Blackstone and they said it was completely fine.
Every time we ran a stock car engine with Synthetic, it blew up within a couple of races. So in my Running Dino oil, we get full seasons out of them. I couldn't give a crap what the factories or oil companies say their test results are. They are trying to sell their product. I use real world testing and synthetics let us down every time. I'm not changing, ever.
Synthetic oil is engineered to be better than conventional oil. It has better anti-wear and lubricating properties. I would never run any conventional oils in my engines anymore, ever, nor will any service manuals recommend it when a synthetic is available. The statements above saying that synthetic should not be used for break in or that it will cause rings not to seat are FALSE. Use a quality break in oil or quality synthetic oil for breaking in your new engine.
MuhThugga hit the nail on the head, the old wives tales about synthetic are just that, wives tales.
My final .02 on this topic. If you do not have REAL world experience with full blown race engines that see the abuse we put them through, then your opinions and factory recommendations mean crap to someone like me. I've been racing for nearly 30 years. Engines run from 1 hour in our stock cars to over 8 hours in our road race cars, high rpm, max hp allowed by the rules, very high heat inside the engine ect, ect. I have this experience. So some of you guys can keep reading your specs and books and do whatever they say. Ill do and use what I know works and has never failed me.
To the OP, I would talk to actual engine builders. Texas speed is one and there are others on here as well. I myself have over 30 years building engines up to and over 1000 crank hp. I was a service tech for Ford and Nissan and also owned my own shop at one time.
Synthetic does have its place in street driven daily drivers that will never really be punished. That's what the factories sell, daily drivers. Yes, conventional oil can and will break down at a certain temp, but that breakdown is slow and you can save an engine when you see the signs. We also change the oil after every race, so we don't have any issues of build up due to the oil being over heated. The issue with synthetic is that when it reaches that high temp where the breakdown happens, it fails super fast. It goes from oil to basically water. There is no protection and the engine blows up.
This is the last race I ran Synthetic oil.
THIS
Turned into this when I spun on the front straight and smacked the concrete wall with the left rear. It cost me a rear clip. The only thing that was saved from the engine was the intake.
Every time we ran a stock car engine with Synthetic, it blew up within a couple of races. So in my Running Dino oil, we get full seasons out of them. I couldn't give a crap what the factories or oil companies say their test results are. They are trying to sell their product. I use real world testing and synthetics let us down every time. I'm not changing, ever.
Blackstone isn't trying to sell anything. They just analyze the oil and tell you what they see. Airplane owners use their services all the time to keep an eye on the engine wear.
07-27-2016, 01:46 PM
Can You Use Synthetic Oil to Break in a 5.3? 
