Hello, just wondering if its ok to run mobil-1 syn oil in a fresh rebuild, or wait until the rings seat? thanks, tom

 

See Vader's response to this post https://www.thirdgen.org/techbb2/sho...threadid=74528 .

At step 12, it's safe to go to synthetic.

If you have a roller lifter cam, you can skip the 2000-2500 RPM step.

 

IMHO it's perfectly OK to use it from the start, that's what I do... that's also what GM has been doing with high-perf motors (specifically Vettes) for the last decade and a half or so.

 

Now, all LS1's come with mobil one form the factory...Just fyi...
And I have always changed my oil at 500 miles on new engine(car) to mobil one, with no engine problems, ever.

 

Mac,

If I understand your question, yes, use synthetoc from the start. There is one caveat. If you have a fresh build and are breaking it in from a cold start, you're probably going to drain the oil after a few hours of running anyway, so synthetic just doesn't make a lot of sense for the initial start and break in. After the run in and first oil drain (to get out all the junk you left behind and any fresh metal) you can use synthetic if you wish. If you're using hard chrome faces rings in a polished bore, you might notice a little more oil consumption than you may expect, but it will seal and stop burning eventually.

 

I'm from the "old school" where "you can't change your oil enough times while breaking your motor in". I would probably have changed my oil a couple of times more before 3,000 miles (once at 500, another at 1,500 and another at 3,000 on top of the inital 20 minute breakin).

So, as Vadar said, it wouldn't make sense to use expensive oil before 3,000 miles.

 

I forgot to mention...

It's only OK to use synthetic in a roller cam motor. Flat tappets will not assume the correct wear pattern with the cam lobes using synthetic. If you are running a flat tappet cam, you MUST use dino juice for the first few hours of operation, so that the lifters are forced to rotate in their bores as the cam rotates under them.

Rings are never an issue.

 

I'll probably be dumping a couple of changes of oil through the engine when its first fired up...
Especially if we break it in on the water brake dyno as planned. I plan on using Mobil 1 for the simple fact that I've not used anything else since 1990.

BTW, after 18 months of waiting, the engine shop called this afternoon to inform me that they were staggering the rod bearing clearances on the shortblock... That means we're probably only a week away from having a completed 385 shortblock!

 

i'm sure it's ok to do, and i have done it with the little 5hp briggs engines on my karts back when i was running them. i just have a hard time doing it on a engine for a car or truck. i like to use 309w for the first 1000 miles or so.

 

rb83l69, are you saying that i can't use synthetic oil if i have a flat tappet cam?

 

309w? Flows a little slower than solid coal?

 

mck-

Only not for break-in. After the first few hours of operation, you can use it, like at the 1st oil change at 500 miles or 1000 miles or whenever you do it. I usually do my first change at 1000. A flat-tappet cam will not break in properly with synthetic oil.

 

ok, thx for clearing that up. i have a flat tappet cam with appx 350 miles on it. i changed oil with appx 250 miles on it. it is not a daily driver, just a weekend hobby car. thx all, tom

 

well the guy that just built my engine told me to run 500 km's with the oil he put in and then change to mobil 1 and change every 5000km's.. also he picked my motor up last week-end and it might site for another 4-5 weeks before I put it in.. he had primed it for me and told me even if it sat that long that I wouldn't have to prime it again before I start it.. dunno if that's good or not..

 

not true.. you can use full synthetic on a flat tappet cam and it will break in just fine as long as you add a high zinc and molly additive form like Lucas oil.

 

Same here amidst everyone saying the rings wont seat blah blah.

Get it tuned, warmed up and go get some heat in that motor get into it a little bit they will seat.

With the fine hone finishes close tolerances and metallurgies of today imo running syn right off the bat should be fine.

At the end of the day either one is fine.