Acceptable Oil Consumption
 

My engine was rebuilt end of last year. Pulls 13-14 inches of vacum at idle. Putting my hand over the breathers on the valve covers i dont feel any blow by. But every time i run my boat i have to add at least a qt of oil. i figure its burning somewhere around a qt every 10 hours or so. I am running Royal Purple 20w50 HPS. Does this seem too high or is is normal for a synthetic motor oil.

That is quite a bit for a 525SC. Mine with 475hrs only used a qt every 25hrs or so.
My 502mpi's use a quart about 15hrs.

one thing i havent checked yet is the pcv valve the sits in the intake that attaches to the top of the blower. wonder if that is sucking too much oil back into the motor

Do a leakdown test, if numbers are high will tell you everything. I ran my blown 502 175 hard hours with run of the mill rings ( J/E plasma) and that thing was eating oil and had crazy leaakdown numbers towards the end, funny thing was it only lost 1-2 mph. Smitty

Did you have the problem prior to using Royal Purple ? I went on a RP binge and put it in my truck , mc and boat . It seems to break down very quick and boat - truck are eating it . More expensive junk in my book , i'm going back to Mobile I which i never had a problem with !!!!!

I did a cold leakdown test earlier this year and was 20-25%. Engine dead cold, i havent done one with the engine warmed up. It doesnt ever seem to smoke or anything either. Before i had the engine gone thru last year i used valvoline racing 20w50 and never had a problem. I used a break in engine oil on the dyno. and have been using royal purple since. I thought about trying a different brand to see if that would make a difference.

I had a similar experience using Brad Penn, motors ate it up. Switched to Valvoline Racing and no more oil consumption.

I had a pick up years ago that when I would run Quaker state oil in the truck would just eat the oil up...switched to another brand and the problem went away...might be worth a try switching brands..

I use Rotella 15w/40 in my 502 MPI. Have never added a drop.

20-25 leakage is 2 much,something is wrong,you should be able to hear the air leaking threw the rings into the crankcase.

One thing to look at is valve guide to valve stem clearance. Sometimes during a rebuild this can be overlooked by some, knurled valve guides, worn valve stems can consume oil. If a leak down shows good, you can check your intake valves with a bore scope after removing carb. Valves should be clean with no oil or deposits. The exhaust valves may show a little oil on stem, this is ok. I usually remove the spiral ring on the exhaust valve stem seal to increase lubrication to guide and stem.

+1. I had the same problem. Change Your oil an give it more break in time. I don't think Your rings will seat with Royal Purple. Artie

thanks for the replies. im gonna try switching oils to see if that makes a difference. Would like to stay with a synthetic. so ill try the Mobil one first. and see how it does. I know the valve stem seals were replaced. ill have to ask my engine builder about the guides. Next time i do a leak down ill warm the engine up first to get a better read.
i would think the engine would be broken in by now. ive put 40-50 hours on it since.

did you break in with the royal purple ? if so there's the problem...NEVER break in with synthetic....always use std for a while...I use rotella, and now I don't even go to syn any more...waste of $$$ my .02

Some times improper break in can glaze the cylinder walls. If you haven't run it at all with break in oil, I'd do a warm leak down and see where your at. The only thing I've heard done once the cylinders are glazed is to pull the motor, tear it down and hit the walls with a fine stone. Maybe someone else has been successful with another process. On the Mobile 1, it's good stuff but don't run the grades for modern motors, use the V-Twin or Diesel versions. Better yet, run Amsoil Dominator.

I use Castrol GTX 20 W 50 in my Merc HP 500 carb engine, seems to do fine, however they are known to loose about a half a qrt when run hard, mine seems to do fine though. I have some Brad Penn I recently bought, but may stay with the Castrol so far it's been fine.

Leakdown on a cold engine doesn't really tell you much IMO. Except maybe the condition of the head gaskets.

I agree with others to switch oil and see what happens then go from there.

The engine was broken in using a specific break in oil made by Lubeatech Advanced Technologies. LAT 20w50. Engine was warmed up on the dyno and we made 7 pulls to 6k rpms on this oil. After the dyno i changed the oil to royal purple and dropped the engine in the boat.

It does seem to burn more oil when im running it harder. My normal cruising speed is 3500-4000 rpms. and at WOT i can spin it to 5400. but it likes to drink way too much fuel at anything higher than 3600. so try to keep it reasonalble.

Im really not ready to pull the motor back apart less than a year later. Figure worse case might foul some plugs out. So if switching oil brands doesnt seem to help ill just let er eat, and keep checking oil level

Let us know your results after getting rid of the Royal Ripoff Snake Oil . We may be able to save someone else some of their hard earned money . :helmet:

an easy indication of worn valve guides is after the engine is fully warmed up, shut it off swim around for an hour then watch out your exhaust as you start it back up if you get a brief puff of blue smoke your guides are worn

i normally dont see much smoke at start up, but will have to pay more attention. The guides i would question because i never had an oil consumption problem untill after the rebuild. Same set of heads