I am dropping in the 355 this week, and I'm wondering what weight oil i should use. i remember reading somthing about a GM oil break-in additive. should i use this? thanks in advance.

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I would use a 30 weight, But it all depends on the engine you built. Did you build a tight or loose motor? You can add the break in additive but I would still change the oil after a couple hundred miles.

 

I've also heard to NOT use synthetic oil during break-ins. The reduced friction offered by synthetic actually prevents the break-in from happening completely.

Jason

 

Yes, Synthetic will prevent the engine from "breaking in". You want to use conventional oil when you first start it up. Wether its 30 wt, 10W-30, whatever, just use conventional. Then when you change the oil, put synthetic in if thats what you want to use.

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i use straight 30w on all the ones i do for me, i've had other people bring me about any weight and brand oil and it's all worked fine. only thing i won't use is synthetic oil in a new engine, or new cam. i like to change the oil after a half hour or so of running.

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ICON Motorsports

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Use a straight 30W oil, I believ Pennzoil is the best out there. As far as not using synthetic oil for startup and break-in that's a big scary story started long ago by someone that didn't know what they were talking about. Synthetic oils can be used in initial startup. GM used to put Mobil 1 in all Corvettes as the initial crankcase fill oil. I don't know if they do anymore or not. The only reason I wouldn't use synthetic is because it only comes in multi-weights. A single weight oil is more stable and is better for break-in.

 

Definitely DO NOT use synthetic on break in, Corvettes are run initially at the factory so when they get to the dealer, they have already had the change from the original oil to synthetic.

 

Here is the URL for the MOBIL 1 site about factory fill.

http://www.mobil.com/mobil1_racing/a...ill/index.html

I submitted a question to their tech department about initial break-in fill as well to set the record straight.

 

The factory fills Corvettes, and I don't know how many other cars, with Mobil 1 synthetic. If you go to Bowling Green and watch them roll off the line (a great road trip - I highly recommend it, I've been a couple of times myself) you will see that they don't change any fluids at all; they ship them with the original fill in them.

If you are running a flat tappet cam, then absolutely DO NOT use synthetic. In that design, the lifters are supposed to rotate as the cam revolves under them; if you use synthetic on initial start-up, there won't be enough friction to make the lfiterrs rotate, they will sit still, and the cam will wear a slot into the base of the lifter. Instead, use a good quality dinosaur juice of your choice, and change to synthetic at the first oil change which should be at the 500-1000 mile mark. Those of us who build racing motors with really stout valve springs will put some lesser springs in for break-in, and save the real deal for after run-in. There are also real low ratio rocker arms available for the same purpose.

On the other hand, if your new motor has a roller cam, then none of this applies. Those are the engines that get synthetic from the factory. No other parts such as rings or bearings are affected one way or the other. They will break in just fine with synthetic.

The engine I drive every day has a roller cam, and has had Mobil 1 since the day it was born. Also, for those of you who aren't familiar with the factory's service procedures, the Vette gets its first recommended oil change at the same interval as any other oil change, which was 3000 miles until this past year, when they upped it to 7500. GMTech would know exactly when this change was made better than me.

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ICON Motorsports

 

use regulare oil like 10w30 to brake in the cam un less its a roller, after a 20 minute brake in on the cam change the oil and filter and put in 5 or 10w30 until the motor is briken in, aboot 750 miles, after the motor is broken in you can, if you wish, use sysentic oil. like said in previos post sysentic oil will not alow the the rings to seat.

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Synthetic oil DOES NOT affect ring break-in. If it did, the factory would not be filling new cars with it.

You may use it as initial fill in a roller-cam equipped engine with the same excellent results the factory gets.

How did that urban legend get started anyway? Maybe the same guy that started the one about Microsoft giving away $5000 to everybody that sent that chain letter around? A few of us didn't fall for that one either...

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"So many Mustangs, so little time..."
ICON Motorsports

 

I don't see why you don't just use the SAME brand/weight oil to break in the engine that you're going to be using on a regular basis! If the oil isn't good enough to use during break-in, then it's probably not good enough to use at all!!!

 

<a href="http://hotbot.lycos.com/director.asp?target=http%3A%2F%2Fwww%2Eseansa4page%2Ecom%2Fresource%2Fbreakin%2Ehtml&id=8&userid=J9S4vbo67QBr&q=MT=engine+break+in+why+not+synthetic&r s ource=INK">Engine break in FAQ</a>

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[This message has been edited by JPrevost (edited April 08, 2001).]

 

Here is the response from Mobil, I asked a follow up question specifically about flat-tappet cams, I'll post that reply when I get it.

Today's engines are built with much tighter tolerances and much improved machining compared to the engines of 10 and 20 years ago. The old concept of "engine break-in" involved two primary elements:

- Removing any metal flashing (called swarf) or abrasive material left inside the engine.
- Allowing valves and rings to "seat" properly.

Today's engines do not require these break-in periods. In fact, Mobil 1 has shown excellent control of oil consumption in the industry standard ASTM Sequence III E test, which uses a completely rebuilt engine for
each new test run. This includes freshly honed cylinders, new pistons, and new rings (compression and oil control). The engine is exposed to only the test oil after rebuild. The outstanding oil consumption control
of Mobil 1 in this test demonstrates that the old "seating" issue is not of concern in well machined engines. And don't forget that Mobil 1 is used as initial fill on Corvette and Porsche engines.
However, if the engine rebuilder is using older machining equipment or lower quality components, it can leave you with an engine containing swarf or abrasive material inside the engine. In this situation, you would be best served by using a short drain interval on your initial oil fill. Mobil 1 will still work in this situation, but it would be less
expensive to use a conventional oil for this first, short duration fill.