Engine break in oils

We do full engine rebuilds in house on light and medium duty diesel engines and we have heard different opinions on what type of oil to use after going through the initial break in process with break in oil. We currently use Driven for 500 miles for initial ring seating etc. For all normal processes we only use Shaeffer's 5w40 full synthetic, however there is controversy out there about not using synthetic oil on a new motor and only use conventional until it has some real miles on it, we have heard up words of 5,000. The information that I collected from our Shaeffer rep is there shouldn't be any issue with immediately switching to a full syn and should be beneficial to, as how well their product protects internal components. I was just curious if anyone could point me to another form or give any information at all about going full syn off the bat, or if the conventional oil for break in is old wives tale. Any information at all would be greatly appreciated. Thanks guys

Cheers

JE pistons, Mahle pistons, Total Seal, Dsport, Manley and others do not recommend using synthetic oils during break-in process...

Thank you so much for the literature, it is good to see that from the manufacturers. However it also confirms my question. As previously stated we do use Drivin break in oil for the initial process but as stated Manley recommends 2,000-3,000 miles before using syn oils, the Total Seal Piston rings artical says syn can be used after break in is completed but this one doesn't show a break in time, and the Mahle article states: the topic of using conventional vs synthetic for break-in or when to make the switch is a highly opinionated discussion.

I do like their statement further on though of err on the side of caution with conventional oil. As 90% of or gaskets, pistons, and rings are Mahle we will continue our process of using conventional, after the initial break-in change, for the first oil cycle and switch to our synthetic from there out. Again I greatly appreciate the information presented!!!

Well, from what I've red the most important period for breaking-in is first 100-120 km (60-70 miles) only when the fresh hone works the best in terms of filing the piston rings and making them up to the cylinder shape. That's pretty much it when you need friction to be at its minimum to allow rings getting best shape as quickly as possible. After that point you can switch to synthetic oils since the most of the work is already done. Having said that the breaking-in would be still going resulting in compression raise for next 2-3 thousand kilometres but it won't be as critical as first 60-70 miles providing that the proper engine load is applied during that time (no idling, progressive load increase and so on).

The other way for fast break in completion is getting the fresh engine on the dyno as soon as possible. Spending an hour or two under the high load will get most of it done....

There seems to be about as many views on this as there are engine builders.

Some of the factors are the type of engine, the materials used, the valvetrain, how it's being used, etc.

A further complication is you're a business, rather than an individual, and so will have no control on how the client uses the engine when they get it back - plus there are possible warranty concerns leading from that.

For the most part, "running in" oils are mineral based, have a high zonc content to give higher protection for high load areas like the valve train, have low levels (or none) friction modifiers to give more effective 'bedding' of rings and flat cam' followers, have a low detergent level to allow contaminants to drop out, etc.

Most modern oils, especially diesel synthetics, have low levels of zinc to reduce emissions, use friction modifiers for reduced drag and improved power/economy, have high detergent levels to keep contaminants in suspension to be removed by the filter, etc.

Personally, I'd start the engine and bring it up to temperature at a fast idle to break in the cam' and followers (if required) while checking for leaks, etc. then drain and refill with a break in oil and change the filter, then run it for 1-200 miles or so of brisk and town driving, then drain with filter change to the full synthetic I'll be using from then on. On the other hand, there were over-night builds that had no 'running in" time and went out with the full synthetic, after the start-up changes.

In your position, perhaps a fill with the running in oil and tell the customer to come back for the "free" (actually priced into the job) oil and filter change and check over, at 500-100 miles, before refilling with the full synthetic you prefer to use - commercial vehicles tend not to be 'babied', so the running in should be done and done bu then. I'd also suggest getting a sample of the oil analysed - again, priced into the job and a good practice anyway - all the heavy equipment I'd worked with in the last 15-20 years had those as part of the warranty process.

There are many cars that are filled with full synthetics right from the start, such as BMWs - but then some of these vehicles are also known to have their manufacturers class what would be called "high" oil consumption as "normal".