Synthetic After Rebuild

[FieroAddict]

I have a fiero that I recently rebuilt the engine in and I would like to switch to Mobil 1 synthetic. I have heard lots about you have to break an engine in on conventional oil before you can switch to synthetic, but no one has really been able to give me a straight answer on how long this break in period should be before I switch over. So far the engine has about 4000km on it since the rebuild. How much further should I go before switching?

Thanks

 

[Ugly3]

Lots of very knowledgable people say to go 10,000 miles on dino before the switch to synthetic. Others, equally knowledgable say go to synthetic as quick as you can.

I can tell you from experience that in my 3 cars I switched to Mobil 1 after 500 miles. All cars have run fine on Mobil 1 for a total of 360,000 miles. In my opinion, there is nothing magical about synthetics, better cold starts, and better ability to handle high temps, that's all.

Good luck with your new engine.

 

[55Test]

Cool, a Fiero guy. You got the 4 or the 6? My brother had an 86 4 cylinder 5 speed, man that engine was noisy.

 

[doitmyself]

My opinionated guess is that the rebuilding process is not as precise as a new, factory built engine regarding cylinder honing, bearing clearances,etc..

I would err on the conservative side and run the dino for 10,000 miles. Why take a risk? Switching to synthetic a few thousand miles earlier isn't going to gain you an extra 100,000 miles of engine life. But, if indeed the syntehtic is "too slippery" for the engine to seat in, you will have a less than "excellent" engine for many years.

Just my .02 cents.

 

[JohnBrowning]

I think you should be fine! 4000Km should be more then enough! If it makes you fill more at ease use a good synthetic blend like Mobil Clean 7500 for one more oil change! IT is as synthetic as most other company's synthetic labled products but it is a GIII/PAO blend and Mobil does not count GIII as synthetic hence the synthetic blend lable!

 

[FieroAddict]

Is there any evidence or proof that switching to synthetic too early can cause damage?

 

[doitmyself]

It probably depends on application. My John Deere farm tractors come from the factory with a special break in oil. They recommend not changing to their 15W40 Plus 50 oil until after 100 hours. They also recommend NOT using their Plus 50 in a rebuilt engine for 100 hours.

I talked to my JD dealer service manager about this after we purchased our last new tractor and he knew of one instance where a person used the Plus 50 in a rebuilt engine and two years later they had to rebuild it again because it never properly broke in.

Of course, you don't have a John Deere diesel engine in your Fiero, so this example was a waste of my opinion!

What do the engine rebuild shops say??

 

[pscholte]

quote:

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Originally posted by 55:
Cool, a Fiero guy. You got the 4 or the 6? My brother had an 86 4 cylinder 5 speed, man that engine was noisy.

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It was the Pontiac "Iron Duke" engine was it not? Just to play it safe, go 3000 miles and then add the synthetic. I think 10K becomes a target number because a lot of people think that is about the time the engine has fully broken in.

 

[Bob The Builder]

I pose a question. With my Toyota Tacoma, I bought it brand new. I ran it for about 300 miles or so on the stock oil, and then went right to a full synthetic. It was Valvoline for that first oil change. Since then, I have tried a few different oils, all synthetic, but for that last 250,000 miles or so, I have used Castrol G III synthetic, and now recently Mobil 1 EP 10w-30. The question I pose is this; Why do I not have any engine wear, leaks, or oil consumption? This truck still drives hard, and I have never topped off the oil except one time when I tried regular Mobil 1 around 150,000 miles or so. Before and after this episode, nothing added between intervals. And mind you sometimes I will go to around 10 or 15,000 miles on the oil depending on how it looks on the dipstick. (Never followed mileage for oil changes)

How does one explain this, because I constantly hear about how one is supposed to allow for proper breakin of the engine parts?

Just some thoughts.

BtB

 

[pscholte]

quote:

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Originally posted by Bob The Builder:
I pose a question. With my Toyota Tacoma, I bought it brand new. I ran it for about 300 miles or so on the stock oil, and then went right to a full synthetic. It was Valvoline for that first oil change. Since then, I have tried a few different oils, all synthetic, but for that last 250,000 miles or so, I have used Castrol G III synthetic, and now recently Mobil 1 EP 10w-30. The question I pose is this; Why do I not have any engine wear, leaks, or oil consumption? This truck still drives hard, and I have never topped off the oil except one time when I tried regular Mobil 1 around 150,000 miles or so. Before and after this episode, nothing added between intervals. And mind you sometimes I will go to around 10 or 15,000 miles on the oil depending on how it looks on the dipstick. (Never followed mileage for oil changes)

How does one explain this, because I constantly hear about how one is supposed to allow for proper breakin of the engine parts?

Just some thoughts.

BtB

---

Bob,

You need to understand that there are a lot of variables involved in why engine A does this and engine B does that: variabilities in the manufacturing process; actual demands placed on the engine, etc. Your next door neighbor could have had an identical truck and followed an identical pattern and had just the opposite experience as you. Conversely someone else could have done the opposite of what you did: used dino until 10000 miles, never varied in brand and weight other than the dino to syn transition and had an engine without leaks or consumption...or they could have followed the regimen I described and had nothing but problems. Only a few things about this "business" are sure: run the engine dry and it will "blow up" on you; overfill it greatly and the will aerate, which could cause oil pump cavitaion, use the wrong grade/spec or leave the oil in too long and you will probably get sludge. If you are looking for a lot of hard and fast rules other than these, you will be disappointed.

 

[unDummy]

quote:

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Originally posted by FieroAddict:
Is there any evidence or proof that switching to synthetic too early can cause damage?

---

I haven't seen any proof or evidence.
I think that initial driving style on the rebuild is more important then oil choice. Also, I always recommend a few quick oil changes to rince out anything in the engine.

I've used synthetic oil in brand new engines without any oil consumption or break-in problems.

I also find that engines that have problems are usually rebuilt with discount parts and/or have poor machining/assembly quality.

 

[JohnBrowning]

I go to synthetic almost right away like at 500-1000 miles in all of my new cars and trucks and no problem. I broke one 22RE engine in on Castrol 5W50 before they switd to GIII and I had no problems with it either. A lot of new cars come with Synthetic fromt the factory. I truly think you are fine at 4000Km! My only reservation about haveing people go to synthetics is that they are able to run it to the normal OCI that they use. No sense going to a synthetic if you still plan on changeing out the oil early!

 

[Donald]

BobtheBuilder - new engines from the major car companies are built with such advanced machines that they are probably broken in by the time they are loaded on the truck for transport. Not true of rebuilt engines however. So in 300 miles your engine was entirely broken in.

 

[bbobynski]

I think the oldwives tale of not using synthetic for breakin because it is "too slippery" was invented by the synthetic oil industry to make their product sound good. There seems to be no real scientific or practical reason for that.

GM ships several thousand engines every day that are filled from the factory with Mobil 1 and they break-in fine.....hmmm...

I have reviewed teardown engines from dyno test broken-in with conventional and synthetic oils and there is no difference.

What needs to "break in" anyway...??? Bearings and such certainly do not breakin as they look brand new 50K later and are completely unmarked. The cylinder wall finish is scraped by the rings and any asperities are removed in about the first few minutes of operation and synthetic isn't going to prevent that from happening. The rings don't change much, actually, despite conjecture to the opposite theory. Since the rings move around and rotate on the piston anyway, the idea of them "breaking in" to a particular spot on the cylinder walls is not correct. The lifters must burnish and mate to the cam lobes which would be the major breakin or wear item on a flat follower engine but that wouldn't affect performance if it didn't ever "break in.." There really isn't much to break in per se and what there is will do fine with synthetic or otherwise.


Some engine makers put added anti-wear compounds in the factory fill oil for breakin. This takes the form of fortified assembly lube on the parts that then dissolves in the oil and stays in for the first oil fill. Sometimes the advice for a particular engine might be to keep the "break in" oil in the engine for a certain period of time not to allow it to wear to break in but to keep the higher levels of anti-wear protection in the oil until all lifters burnished, distributor gears burnished, etc....depending on the engine design and features.

 

[Dr. T]

Yeah, just like the 5x greater film strengh!