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Okay guys..

I decided to use the Esso Ultron (synthetic oil)5W-40, or maybe the Castrol SLX 0W-30, in my rebuilded and blueprinted KL engine...seems like the HLA's doesn't like thick oils

But I still have a question....I saw in Probetalk, and even around here, that I should use a mineral oil when I rebuild an engine for at least 10.000Km before change it to a full synthetic oil.... Is this right? Or can I start to use a synthetic right now?

thanks again folks!!

I'd say its your call. Tons of new cars come with synthetic from the factory now. Could be a good thing, could be bad.

If the bebuild included honing the cylinders and getting oversized rings, I'd run through 2,000 - 3,000 miles on regular oil just to be safe, then go from there with the synthetic.

MOst new/rebuilt engines create more heat during the break in period, correct?

Well, since sythetic oil is much more resilant to heat and soot then regular oil, I don't see where the questioning comes from. Synth is a better oil for your enigne, and always will be superior than it's counter part (slight excpetion for high mileage engine that used regular oil most of it's life).

Use a 20W50 mineral oil for about the first 3000 miles. It will help to seat the rings. A 0 weight oil is not a good choice in my opinion. Especially when trying to break in a newly rebuilt motor. It's too unstable for daily driving.

I would recommend using dino oil in first until the rings break in. It will take longer with the synthetic oil. When I build my KL last year I ran 10w-30 pennzoil for the first 500 miles and changed it then ran it for 3k then switched to Mobil 1.

Also, ring seat time is all dependant on which type of material you went with. (ie. Cast Iron, Chromoly)

Originally posted by MX3-Freak:
MOst new/rebuilt engines create more heat during the break in period, correct?

Well, since sythetic oil is much more resilant to heat and soot then regular oil, I don't see where the questioning comes from. Synth is a better oil for your enigne, and always will be superior than it's counter part (slight excpetion for high mileage engine that used regular oil most of it's life).

While I chalk up the whole dino oil break-in thing as urban legend, I figure better safe than sorry. A couple thousand on dino oil won't make a significant difference if the next 100K miles are on a good synthetic.

Thanks a lot for all the info, guys!!

I'll go with dino oil...like Lakersfan1 said...".. I figure better safe than sorry..".

Originally posted by mazdubber:
Use a 20W50 mineral oil for about the first 3000 miles. It will help to seat the rings. A 0 weight oil is not a good choice in my opinion. Especially when trying to break in a newly rebuilt motor. It's too unstable for daily driving.

NEVER use a heavier oil than that recommended in the owners manual. In the summertime, you MIGHT get away with a HDEO (diesel) 15W40 weight for cleaning out an engine, but I would stick to xW30 regardless of whether it's a 0,5, or 10. In a fresh engine, I would run 10W30 for a few thousand miles before switching to the 0W30. The zero is just for warmup purposes anyhow.......to save gas. Look for the Castrol Syntec 0W30 that says "Made in Germany" on the back. It's about the best $4 a quart oil around. The made in USA stuff is junk and a totally Group III oil.

See bobistheoilguy.com for details

Wow..thanks a lot for the help!!

Really like it!