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Discussion Topic:
Oil Pressure / Oil Weight
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6lucky13 |
10-21-2013 @ 3:21 PM
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Member
Posts: 57
Joined: Jun 2011
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I'm planning to switch from 10w-40 motor oil in my '37 engine to 20w-50 oil. Should I expect to see a difference in indicated oil pressure? The motor currently runs at about 20 lbs at idle to 30-35 while driving with the 10w-40. Jon
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Old Henry |
10-21-2013 @ 3:32 PM
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Senior
Posts: 738
Joined: Apr 2010
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I got 5 psi more from changing from S.A.E. 30 to S.A.E. 40 (I don't use multi-vis oil if I can help it.)
Old Henry (The older I get, the better old looks.)
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supereal |
10-21-2013 @ 4:05 PM
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Senior
Posts: 6819
Joined: Oct 2009
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I have used Castrol 20W-50 for years. It helps maintain pressure when the engine is hot, yet allows good cranking when cool. When I take an engine apart using this oil, it is very clean.
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joe b |
10-22-2013 @ 7:00 AM
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Member
Posts: 389
Joined: Oct 2010
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I also have used Castrol 20/50 in my '41 for 16 years. I agree with Super. I did change to 40wt and a quart of Marvel Mystery Oil to try to cure a valve problem. My oil pressure dropped significantly. This attempted fix did not work and I went back to Castrol. Oil pressure is back to what it was.
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keith oh |
10-23-2013 @ 7:44 AM
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New Member
Posts: 116
Joined: May 2010
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I do not know what the rational for using MMO for low oil pressure was, but for your "Valve Problems" dribbling MMO through each side of your carburetor with the engine running at a fast idle stands a much better chance of relieving valve problems.
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joe b |
10-23-2013 @ 1:35 PM
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Member
Posts: 389
Joined: Oct 2010
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Keith, I also did that but it did not fix the problem. Some suggested to use MMO in the oil so I tried it as I thought what have I got to lose?
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supereal |
10-23-2013 @ 8:41 PM
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Senior
Posts: 6819
Joined: Oct 2009
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I wouldn't expect valve problems unless it was confirmed by a dry/wet compression test. MMO may have its uses, but it can, and will, cause spark plug contamination. Adding anything to the fuel or down the carb before properly diagnosing a problem is a waste of time and money. Adding it the oil can result in loss of effectiveness of the package of the oil's carefully engineered additives.
This message was edited by supereal on 10-23-13 @ 8:44 PM
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joe b |
10-24-2013 @ 6:02 AM
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Member
Posts: 389
Joined: Oct 2010
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Super, that is exactly why I changed the oil after about 85 miles with the MMO. Could you explain the "dry-wet" compression test? I have only used the tester dry I think.
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supereal |
10-24-2013 @ 7:45 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Remove all spark plugs from the engine, and block the throttle open. Test each cylinder and note the compression. Then, squirt oil into the cylinder and retest. If the compression goes up, the rings are worn. If not, the valves are not sealing. Doing diagnosis saves lots of time when tracing problems. Just guessing almost always results in complicating the situation.
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supereal |
10-24-2013 @ 7:45 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Remove all spark plugs from the engine, and block the throttle open. Test each cylinder and note the compression. Then, squirt oil into the cylinder and retest. If the compression goes up, the rings are worn. If not, the valves are not sealing. Doing diagnosis saves lots of time when tracing problems. Just guessing almost always results in complicating the situation.
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