Do I need running in oil as I'm just about to rebuild my engine and have heard so many horror story's of engines only lasting a few hundred miles after a rebuild and was wondering if this was down to not using the right oil or just people making mistakes etc when rebuilding them.

 

useing millers runing in oil when mines is complete

 

So many different opinions on this.

I've just built a new engine. I used a semi synthetic 15/40 for 200 miles. The first 25 were fairly gentle up and down the revs, no boost. The rest were then 1 bar and 7-8k rpm. I've dropped the oil changed the filter and run fully Synth since and its the first engine I've had that uses next to no oil. I will never use the gentle run in method ever again.

 

The only thing that really needs running in on modern engines is the rings, you need a non synthetic oil to bed them in, Millers is fine, I just use a cheap 15/40 mineral oil.

 

Plus, the engine failing thing is no doubt more down to the non-disconnecting of the crank sensor during oil changes.

This, too, splits owners firmly down the middle - do a search and decide for yourself.....

 

youve got me thinking now daz about my 1000 mile run in period lol think a might go down your route will this b ok for my 2.3

 

Put it this way, Duncan Graham's 2.3 had done 2miles before it arrived at Snetterton for the final round of TA. It was "run in" on the practice session at low boost (1.5bar) we dropped the oil changed the filter and it was Mapped on the warmup session.

It hasn't used a drop of oil and is one of the quietest Subaru engines I've ever heard.

As I stated earlier I will always do a gentle first few miles up and down the revs through the gears. 20-25 miles I reckon on a semi synth oil. Then Its boost and revs time for 150 or so miles. Drop the oil change the filter fully synth and then map it and nail it

 

On all the engines i build & run in i use a cheap semi synthetic oil, run them on low boost for 500 miles to bed the rings, & change to full synthetic, never had any oil issues or blowby.
If you run for to much mileage on mineral oil it damages the big ends, just use semi & run them harder.
The most common reason's an engine fails at low mileage after a rebuild is it was'nt cleaned properly, & reusing the modine cooler, thats assuming it was bolted together ok with correct clearences.

 

I take it the modine cooler is another word for oil cooler is it? If this is cleaned properly should it really need to be replaced? If I'm changing that then I should change the oil pump aswell should I? Thanks for all the help.

 

This is exactly why i mentioned the modine oil cooler, as you cannot succesfully clean them out, especially after any sort bearing failure, i know there not cheap, but in the bigger picture of an engine rebuild its a small price to pay.
Any rebuild from a well used engine should require a new pump.

 

would castrol 10w40 semi synthetic be ok for running in a newly built engine?

 

Lets be fair, its so easy to do that you'd be a fool not to, just in case.

 

I totally agree.