When should i switch from conventional to synthetic...

[dirtwarrior17]

oil on a new motor? The builder told me to take it easy on it then change the oil at 500 miles. Can i switch to synthetic at 500 miles or do i need to wait?

If so when can run synthetic?

 

[R72K5]

i have same Q because the 350 in the 80 c-20 i am getting has 1300 miles on it after total rebuild, bearings rings and all,

i wonder the same thing about what oil to run,

maybe some mobil 1 ?

thanks

 

[Robert79K5]

I put synthetic in my 355 right after the initial break-in oil change. I built that engine eight years ago and its been in two trucks. Some engines come from the factory with synthetic in them so I wouldn't worry about putting it in too soon.

Iv heard people say that synthetic is too slippery and that you should break the engine in on fossil base oil then switch to synthetic, but I beleave thats just crazy if you break it in right.
But thats just what I personally believe so YMMV

 

[HarryH3]

It depends on the rings that were used. Moly rings are HARD and take much longer to wear to match the cylinder walls. I've read that synthetic oil can prevent that from happening. Iron rings will seat much quicker.

Also, your local machine shop doesn't have the resources that General Motors has when it comes to assembling a close tolerance engine. So expect that the clearances won't be nearly as close as in a brand new Corvette.

 

[coptezr]

when i put my first 500 miles on my motor then i put synthetic in.

 

[Eric M.]

I was always under the impression that Synthetic would last longer and withstand higher operating temps. (like racing applications) before breaking down. I never heard that is was "more slippery". I was told you could go 10K miles between oil changes without fear of breakdown. BUT, in daily driving situations, you'd want to stick to 3K to 5K because the oil gets dirty / comtaminated even with the best of filters way before 10K and dirty Synthetic isn't any better than dirty fossil based oil.

Eric M.

 

[73k5blazer]

I thought it was the other way around. Moly rings are somewhat pourous and have better oil retention, better resistance to higher temperatures and therefor seat much quicker, but require a carefull break-in. Plain cast rings take alot longer to seat, you don't have to be as careful, but it will burn a little oil until they are seated which is usally several thousand miles. Moly rings seat much quicker, 500-1000mi.
Chrome rings are very hard, take a long time to seat but are great for high containmnent envoironments due to thier hardness and resistance to holding on to contaminents.

Reference:


http://www.hastingsmfg.com/Service%20Tips/ring_set_composition_recommendat.htm

 

[Mad-Dog]

After the rings are seated.........

 

[dirtwarrior17]

does 500 miles sound right for moly rings? The block is an lt1.

 

[Mad-Dog]

mileage may vary, a good sign the rings are seated is a reduction in blowby.
new motors tend to have excessive blowby until the rings are seated.....