View Full Version : Break In Oil

01-30-05, 07:09 PM
I purchased a brand new, in the crate Northstar for my 94 Seville. I am a big fan of Mobile One Synthetic oil. Is it ok to break the engine in on Mobile One or should the break in be done with mineral oil?

01-30-05, 07:28 PM
If you really want to use it, Mobil 1 is fine for breakin. GM has factory filled tens of thousands of engines with Mobil 1 and they break in fine...

01-30-05, 07:41 PM
Thanks, BBob. They used to tell you that the rings would not seat with synthetics. I think I'm going to try it.

Carl Creque

01-30-05, 08:25 PM
I would not reccommend using synthetic for break in. I have seen ( and heard stories of ) engines taking way to long to break in if synthetic is introduced too soon. When I bought my truck ( brand new ) I changed the oil promptly at 500 miles. Again at 1,000. I actually ran the dino oil until it had 20,000 on it to insure proper break in. It's your engine, and that's just my opinion.....

01-30-05, 10:08 PM
I have seen ( and heard stories of ) engines taking way to long to break in if synthetic is introduced too soon.

What, exactly, does it mean that an engine "took too long" to break in? Since you've personally seen this, I'm very curious about what you define as break in, what are the indications that it's done, and when should it be finished? If that's such a problem, why do they put synthetics in new Corvettes and Vipers at the factory? Wouldn't their break in take too long? I've never heard of that as a problem on those cars. Is it? I have always heard that the first oil change is the most important, and 500 miles is the number most often quoted by various sources. What kind of stuff winds up in the oil during that first oil life interval that it's so important to change it?

01-30-05, 10:16 PM
We used to hear the same stuff slung around about breaking in aircraft engines only it was ashless dispersant oils vs. straight mineral. Aircraft engine manufacturers essentially say, "Don't baby it". Like Bbob says GM thinks you ought to break it in with Mobil1 oil and follow the oil change display. I have 8000 miles on mine and it hasn't burned a quart yet. If it ain't broke don't fix it. Why argue with success. Don't be stomping on pissants while elephants are running up and down the halls.

01-30-05, 11:36 PM
All the RWD Northstars get factory filled with Mobil 1 in the STS/XLR/SRX. So do the DOHC V-6's with VVT in the CTS. So have Corvettes for many years. Wonder how they all manage to break in fine....????

I, too, have always heard the old wives tale of not using synthetic for breakin. No one told the guys a Mobil about it because they just laugh when you mention it to them. Trouble is, no one can ever explain exactly what aspect of synthetic oil that makes the engine not want to break in....Since the only real performance difference in the synthetic products is the resistence to oxidation at temps above 300 degrees F I don't see how this affects the breakin.

01-31-05, 03:23 PM
It all depends on what you are "breaking in". At the cam/lifter interface in flat tappet stuff, the slicker the lube is the better at every point in its life. Being the most highly loaded spot is a modern engine, "break in" here means getting it past the first few critical minutes w/o failure, hence the advice to not let the rpms drop below 2500-3000 for the first 20 or 30 minutes in a SBC, for instance.

If we are talking about breaking in the rings/cylinder walls it becomes more complex. In an older technology motor, especially one with chrome rings, it is/was necessary to have the oil film break down slightly to get the ring/wall interface to literally "wear in" to each other in order to get a suitable seal that would keep compression on one side of the ring pack and oil on the other. (I understand that this is a highly simplified view of the situation) In order to get the very hard chrome face of the ring to wear at all, a rather aggressive cylinder wall finish was used. The break-in recomendation for minimizing constant speed/constant load conditions and snapping the throttle closed, getting on and off the throttle, varying load and speed, etc. were all an effort to get gentle wear of the rings and then a flood of oil. That is why the first oil change at 500 miles was/is so important. It will be full of trash that we probably won't be able to see.

Using too "slick" of an oil in a motor that requires this type of break in may well cause the rings to "glaze" and never seat properly. I have only had this happen with 2 out of a hundred or so engines that I have built over the years and both were filled with Castrol XLR, which is no longer available. It was a very slick oil and cost $1.25 a quart in 1970 which was about 4 times the cost of Penzoil. I never saw a bearing failure on any motor with XLR in the sump. This includes endurance racing of up to 8 hours.

Both of these motors passed oil and required a tear down and a new set of rings in a deglazed block. Needless to say I will NEVER put good oil in a new motor again.

Does this apply to new factory cars? Probably not. The control over bore finish and straightness today are the stuff of science fiction 20 years ago. (It should be noted that the aftermarket cannot duplicate this level of work.) Today, cars are made with a very smooth wall finish, and rings that have a much, much better seal, right out of the box. There is much less of a need to worry about whether the rings will seat than in days past. A new car these days probably has a better ring seal before it starts than a car did at 10,000 miles in 1975.

The upshot of all this is that new cars with high tech motors like the N* probably don't require the non-detergent, poor quality oil for the first 500 miles, as we needed in days of yore to get a good ring seal with hard chrome rings. Any kind of aftermarket engine or rebuild may well require it for a quick, sure seal of hard rings. I have seen chrome rings take 20,000 miles to seat with the wrong (too smooth) wall finish.

Today I still would recommend cheap dino oil for the first 500 miles, but I am working hard at not having to tear a third new motor apart for rings at 3000 miles.

01-31-05, 07:03 PM
How do you guys feel about the use of GM EOS during the break in period? We always use it in the race engines during break in.

01-31-05, 07:45 PM
Thanks duecentoi, you saved me a bunch of typing! My thoughts exactly!

01-31-05, 11:18 PM
I used straight EOS for assembly oil in aircraft engines for ten years. I used about a can per engine.

01-31-05, 11:24 PM
The GM EOS is an excellent addition to the crankcase for breakin. That is exactly what is was developed for. As mentioned before, the EOS has about 10 times the concentration of the antiwear additive ZDP that normal engine oil has so it is an excellent assembly lube and break in lube to prevent wear and scuffing at critical wear points during breakin.

I think the myth of not using synthetic oil for breakin was started by the synthetic oil marketers as a backhanded way of saying how "good" their product was....LOL... Imagine, this stuff is SO good and SO slippery that it won't even let an engine break in properly..... LOL LOL LOL

Reminds me of the STP trick of dipping a flat blade screwdriver tip in it and asking someone to try and hold the screwdriver just by squeezing the tip. You cant hang onto it. This was supposed to "prove" how good STP was. Not that gripping a screw driver with STP on it is relevent in any way to what goes on in an engine...but it was a neat trick.

01-31-05, 11:48 PM
So, from what I can gather here so far from the hands-on and the engineering opinions, newer technology engines, which probably include the Northstar, should not have the same problems with break-in that older technology engines with chrome rings had, and therefore synthetic lubricants should be just fine for break-in periods.

If it was me buying a new car (yeah, like I could afford that) I would leave the crankcase alone until 500 miles, then change on a regular basis with whatever oil you believe to be best based on the approximately 100 trillion different opinions available from everyone who can pronounce the word "oil" in any language.

Reminds me of the STP trick of dipping a flat blade screwdriver tip in it and asking someone to try and hold the screwdriver just by squeezing the tip. You cant hang onto it. This was supposed to "prove" how good STP was. Not that gripping a screw driver with STP on it is relevent in any way to what goes on in an engine...but it was a neat trick.

LOL That's a good one... So let's do a little STP reasoning here: Engine deposits can indicate or cause problems, and those deposits are probably pretty greasy because they're inside the engine, and I can't hold a screwdriver after I dip it in Dawn dishwashing detergent, and Dawn takes grease out of your way, so therefore I'm switching to Dawn dishwashing detergent instead of motor oil because it's an excellent lubricant and it gets rid of engine deposits. (Disclaimer: If you ruin the engines in every vehicle you own because of this advice, just remember, it was Bbobynski's idea) :rolleyes:

Michael Cowden

02-01-05, 12:46 AM
STP and Andy Granatelli paid the biggest consumer fraud fine in history. I think it was about $668,000. The FTC claimed that the only thing STP was good for was to put money in Andy Granatelli's pockets. At the time he was getting about $3.50 a can for the stuff he was paying about $.50/gal. by the drum.