What oil to use when starting a fresh motor?
 

What is the best oil, weight, etc. to use to break in a newly rebuilt engine? Any suggestions are appreciated.

Thanks.

i used castrol gtx 10-40

As long as it is detergent, and non-synthetic.

I thought I remembered someone saying a straight weight is best for breakin, but wasn't sure.

I always use 30W for the first hour, then swap to 10/40. I do this just to clean the engine out.

I put 6 quarts of valoline 10W40 in mine and change it out at 500 miles then 3000 from then on.

I only overfill the engine by a quart the first time for break in.

I'm breaking in my new 292 with 6 quarts of Napa straight 30 SAE non-detergent for the first 100 miles, then switching to detergent 30 weight. I will also add the 8 oz bottle of GM break-in oil (EOS).

That is what I was always told. Straight 30, non-detergent for cam break-in and 50 miles after that. Then switch to detergent straight 30. I then dump that at 500 more miles and switch to 10-30 for the rest of the engines life.

Gm's EOS (engine oil suppliment) with your normal weight oil.

I've heard it is best to use dino oil on a new engine, but then again the Corvette and exotics use Mobil 1 from the start with no issues :burnout:

vettes have roller cams. , I use store brand 30 weight and EOS//for the first 20 miles or 20 minuts,which ever comes first..then mobile one synthetic. If the rings are not seated by the time the cam is broke in..somethings wrong

Valvoline 30 wt with GM Engine oil supplement for the first 50 miles/50 minutes. 30 wt Valvoline, changed again @500 miles, 1500, then every 2000 to 3000 miles thereafter. One engine I have done this to just ticked over 150,000 since the rebuild. Can't complain about that.

10 W 30 Valvoline Never Had A Failure Yet???

Is there much value in using the GM EOS ? I have purchased several GM crate motors in the past and have been forced to purchase it when I purchase the crate motor by the GM parts guy. He says you won't get the warranty if you don't buy it. I have always dumped it in with the oil during the break in period. Just wondering??

Never use a ND oil in a modern engine. They don't generally have the anti-wear and anti corrosion additives necessary to fully protect your engine. GM's EOS is loaded with anti wear agents, which may offset this to some extent........but there is just no reason to use a ND oil. Some very old engines with rope seals are not compatible with detergent oils, but these engines are few are far between.