How do i break in new engine parts if i've already been using synthetic oils?

Question

I own a 95 Mustang Cobra with a 5.0. For as long as I've own the car (over 4 years) I've use either Royal Purple or Mobil 1 synthetic oil. Im in the process of putting in a new cam, lifters, push rods, heads and upper/lower intake manafold. I've noticed that its recommended to use conventional oil to break in new components but I've also been told that once you start using synthetics you cant go back. What oil should i use to break in the engine?

Answer 1

There is no reason that you cannot go back and forth between the two types of oil.

Answer 2

Synthetic oil was originally developed for high performance racing engines. Mobil tried to popularize synthetic oil for passenger vehicles back in the early 1970's. At the time, Mobil was promoting 20K or 25K oil changes with synthetic, but they soon backed down from this. Synthetic oil is a good choice if you have a vehicle with a high performance engine (in fact synthetic is required for many of these engines). It is also a good choice if your vehicle is operated in extremely cold climates. It has higher resistance to breakdown caused by heat and it flows better in extreme cold. Unfortunately for the synthetic oil industry there is virtually no advantage to using synthetic oil in a non-high performance engine that is operated in moderate climates. You probably could go a bit longer between oil changes with a synthetic, i.e. following the normal service schedule even if you fall into the severe service category, but I wouldn't advise this. In short, synthetic may give you the peace of mind of knowing that you are using an oil that is far better than necessary for your vehicle, but it won't reduce wear or extend the life of the engine. The mistake some people make it to wrongly extrapolate these benefits onto normal engines operated in mild climates, with the ultimate lack of any knowledge being manifested with statements such as "synthetics provide 'Peace of Mind,' or 'Cheap Insurance,'" or other such nonsense.



API Certification, Phosphorus & ZDDP
Never use a non-API certified synthetic oil (there are many of these on the market). The problem with the non-API certified synthetics is that they contain too much phosphorus (in the form of the additive ZDDP (Zinc Dialkyl Dithiophosphates)). The API has limited the amount of phosphorus because phosphorus shortens the life of the catalytic converter. These oils are fine for snowmobiles, motorcycles, and older cars that don't have a catalytic converter, and the extra ZDDP does provide additional wear protection. Unfortunately, the marketers of some the non-certified oils do not explicitly and honestly state the reason for the lack of API certification. You can check the status of API certification on the API web site. Be certain to go not just by the manufacturer name but by the actual product as well. This is because a manufacturer will sometimes have both certified and non-certified products. Suffice it to say that Mobil 1, Royal Purple, Castrol, & Havoline all make synthetic oils that are API certified and that can be purchased at auto parts stores and other retail outlets. Amsoil has one product line, XL-7500 that is API certified, but it's other lines contain too much ZDDP to be certified and should not be used in vehicles with catalytic converters.

Answer 3

You'll probably install that new cam & lifters with some sort of assembly lube - like the molybdenum variety. You'll fill it with good quality conventional oil and break it in carefully.

As soon as you're sure it's broke in properly, you'll need to change the oil & filter to remove the assembly grease that's in the oil pan.

That's when you can start using your outrageously expensive synthetics. There is no law that you can't go back to natural oils.

Answer 4

you can switch oils anytime you want and it won't hurt a thing, you will be breaking in a new cam so I would make sure you have plenty of cam lube on it before you put it in and go with regular oil, it only takes about 20 minutes to a half hour to break in a new cam, just be sure to not let the idle go below 1,500 RPM for that length of time and after the half hour you can drain the regular oil out and put your synthetic back in and everything will be fine.

Answer 5

People say not to use synthetic in new engines so the rings will seat faster. You don't have to worry about it with the stuff you did.
And the old wives tale that you can't go back to regular oil when you've used synthetic should have died decades ago.

Answer 6

you CAN switch back and forth or mix the two, check out 10 myths about synthetic oil: http://www.amsoil.com/redirect.cgi?zo=1463115&page=articlespr/articlemyths

use conventional oil to ensure proper break-in of your cam, then go back to synthetic, Amsoil is good stuff: http://www.amsoil.com/redirect.cgi?zo=1463115&page=performancetests/g1971/index