Oil pressure question

[Peter]

Hi all,

The Maintenance Manual describes in winter layup that one should warm up the engine nicely, drain the oil, and replace with a quart of MMO. And this also “facilitates recommissioning in the spring when you only need to add enough new oil to bring the level to the full mark.”

I have followed this procedure for the last two seasons and my oil pressure has been on the lower side compared to when I ran with no MMO in the oil.

Previously I would get 60 lbs on start up and 40 when warmed up. Now I get 40 lbs on startup and it sags to 30 when warmed up and down to 20 at idle.

Do you folks change the oil in spring to remove the MMO?

Will the MMO evaporate as time goes on and I will then top up with regular oil?

The exhaust smells lovely (MMO in fuel too) but not as nice as castor oil that I used to smell at the race track.

Engine started beautifully this spring and runs like a top. Am I being a Nervous Nellie?

Appreciate your wise advice!

Peter

[joe_db]

I have never done anything like that. I just change the oil in the fall and use that oil until the next fall or 100 hours, whichever comes first.

[Dave Neptune]

Peter, when you changed the oil did you always use the same "weight and grade" of oil? And did you always have the same percentage of MMO in the oil upon your start up?

The numbers are not bad at all, at least nothing to worry about.

Frankly I do not and have not used MMO in my oil ever. The MMO is a hi-detergent type of oil and was good 75 years ago when there was nothing available in "detergent oils" like today. There are far better lubricants today for top oils in the fuel too. It is good for soaking rings if there stuck which seldom happens with todays "modern" and superior detergent oils unless there was water encroachment. IMHO

Dave Neptune

[Peter]

Dave,

My notes are not careful enough to answer that question I am afraid.

Maybe just for fun I will change the oil mid season and see if the pressure pops up.

Thanks!

Peter

[joe_db]

Peter, when you changed the oil did you always use the same "weight and grade" of oil? And did you always have the same percentage of MMO in the oil upon your start up?

The numbers are not bad at all, at least nothing to worry about.

Frankly I do not and have not used MMO in my oil ever. The MMO is a hi-detergent type of oil and was good 75 years ago when there was nothing available in "detergent oils" like today. There are far better lubricants today for top oils in the fuel too. It is good for soaking rings if there stuck which seldom happens with todays "modern" and superior detergent oils unless there was water encroachment. IMHO

Dave Neptune

I too have never put MMO in the oil. It is much thinner than the regular lube oil, I have no doubt it would lower the pressure.

[Sam]

I too have never added MMO to oil, fuel yes - oil no. I have had for the last 45yrs a 1966 early model that has never needed rebuilding. It is a short season in Chicago and I usually clock about 25 to 30hrs a year engine time with the longest run being about 6 hrs each way to and from yard ...a lot of shorter runs entering/leaving harbor. I was an engineer and not a chemist but recommend and do change oil mid season and just prior to haul out for winter layup. I use any quality 4qts 10w-30 or 30 with some STP added at spring launch. My layman's understanding from an old mechanic friend is that besides some viscosity thickening it contains extra zinc which aids in improving lubricity and resists corrosion. Oil pressure at start up is about 45psi and settles down to about 35psi and about 25psi at idle. To some [and manual] this may sound a little wasteful but for about an extra $15 and half hr of time I like the idea of clean oil in a non filtered engine. Just my thoughts- hope this helps.

[Boat]

echoing the same as guys above. my climate is pretty mellow here in the PNW compared to some. just an oil change for me in the spring before the season. every 100hrs after that. No MMO in fuel or oil.

[capnward]

I am one of the eccentrics who puts MMO in fuel and oil. I have been doing this for 20 years and well over 3,000 hours since the last rebuild. I understand that it thins the oil and thus makes the oil pressure lower. I often ignore the oil pressure, but it goes from 40 to under 30 psi as it warms up. I change oil every 50 hours, as recommended by the Moyer manual. That is usually 3 or 4 times a year. IMO it is much more important to add MMO to the fuel. I use 2 oz. for every five gallons. I read somewhere in this forum that the old engineers who worked for Universal testing these engines swore by using MMO in the fuel. I may stop putting it in the oil as an experiment. When I do add it, it's 8 oz. added to 3.5 quarts of 'diesel-type' 10w40. which is 7%. I have never needed to open the valve cover. The engine purrs once warmed up, although when I started her up in the spring this year there was a tapping noise that went away after a few minutes. I had not run the engine for five months and put some MMO in the cylinders to soak for a few days before starting.

[Indy]

I just use straight 30 weight, and change in the fall before haul out. At the risk of taking this off topic, is there any concern that with a shared sump and a wet clutch, it may be advantageous to use something like motorcycle oil?

[sastanley]

Indy, I run 5w-40 synthetic "diesel truck" oil in mine.

~55 PSI at startup and settles in about 37-39 PSI when warm. I also have the Indigo oil filter with adjustable oil pressure attachment too, so I've been able to dial mine wherever I want it.

[Surcouf]

... Now I get 40 lbs on startup and it sags to 30 when warmed up and down to 20 at idle.

...

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