Date:         Mon, 2 Jan 2006 13:07:18 -0800
Reply-To:     Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Subject:      Re: New engine decision and break-in questions
In-Reply-To:  <14859BCF-1B05-47C6-84AE-379E6E8D3E60@xochi.com>
Content-Type: text/plain; charset=iso-8859-1

The reason you want to vary your speeds is to change the loads on the piston rings. When you are accelerating, the engine draws lower vaccuum, and the rings set against the cylinder walls harder. When you are on "overrun" or coasting, the engine draws LOTS of vaccuum, and the rings tend to lift away from the walls. Letting the engine fall to idle while in neutral does not allow the extra vaccuum to be developed, and is to be avoided. The oil that is moving around on those ring-and-cylinder surfaces is what is carrying away the steel, aluminum, and iron bits that are being worn off of the high spots of each piece. So, setting the rings, then lifting them, allows the wear bits to be removed by the oil. And, the better way to do this is with the engine at operating temprature as much of the time as possible. Cold starts, and cold running are the hardest things on any engine, and ESPECIALLY a new/rebuilt one. The best oil for break-ins is a non-synthetic, non-detergent straight weight
 oil. Usually, though, the engine cannot be pampered THAT much, so a 10W30 is a compromise. Avoid heavy loads, and hard accelerations, especially with cold oil, because all of the wear points are not taken down yet, and you can break things. Do not lug the engine, nor should you rev it highly. With an "automagic" tranny, it is almost impossible to load heavily at low RPM, so that shouldn't be an issue. Low engine speeds mean low oil flow, and that can be bad. The goal is to have lots of oil moving around to carry the wear bits away  and get them to the filter. The break-in oil should be left in for a short time only, maybe 100 or 200 miles MAX. There is a lot of junk that is knocked off, and you don't want it floating around in your oil. The next oil change can be to you regular oil, but it should also be a shorter-than-normal interval, again because of the junk in it. Break-ins on modern engines are not nearly the problem they used to be, because manufacuring techniques and
 tolerances are MUCH better in general than they used to be. But, it is still important to follow some level of break-in behavior.

  I rebuilt an engine once that the owner ignored the break-in advice, and spun a rod bearing in it within 3 days! Boy, was there hell to pay for that. The owners' father had payed for the rebuild, and now had to do it again, PLUS have the crankshaft reground! Now, I'm not saying this is guaranteed to happen if you don't do things exactly right - he was out doing lawn jobs, neutral drops, etc. before he blew it the first time, and I bet was back at it as soon as he got the car back...


  <snip>
Questions about the break-in procedure: As I understand it, one
should run regular (non-synthetic) oil, and try to avoid driving at
the same RPMs, to help the rings seat in better. Can anyone
explain the theory here? Is it really just RPMs you want to vary?
Or do you want to have a range of RPMs, loads, temperatures, etc?
What are the critical DOs and DONTs? For example, would it better
to do a bunch of short, in town trips? Or maybe a mix of in-town
trips with some longer highway driving? Or, if I was on the
freeway, should I go steady, or occasionally speed up & put it in
neutral and coast for a bit (i have an auto tranny).

-mike




Evan Mac Donald

1984 Wolfburg
1985 GL 7 Pass.
1991 Carat Weekender
1972 Chevy P/U
1993 Bonneville