How about this oil scheme (or Do I need a life? ):

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Motorhome has a 1990 460 V8 which specs oil pressure of 40-65 psi at 2000 rpm hot. I was running a cheapo gauge (by “Make Waves Instrument Corp”) and it read 58 psi hot at 2000 (30 psi idle). I obtained a Sun brand gauge and installed it instead of the cheapo. The sun shows 70 psi hot at 2000 (40 psi idle). I am more inclined to believe the Sun gauge. Anyway, that pressure is above the spec range, so my scheme is to get some HDMO 10w oil to mix in the my crankcase and slightly thin the oil. It takes 6 quarts, so 5 quarts 10w30 with one 10w should net me (I believe the NAPA 10w is 6 cSt) about a 9.5 cSt or a borderline 10w30. What do you think? Probably won’t see much drop in op at a reduction of 1 cSt. Two qts 10w would get down to around 8.1 cSt, which probably is too low.
 
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TallPaul, if you have to ask... [Smile] What's in your stash? Let's see if something you already own might be good for additizing your motorhome oil. I'm thinking perhaps a quart of M1 0W-20 if you have any. [ June 01, 2005, 10:37 AM: Message edited by: bigpaulo ]
 
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That's quite a discrepancy between the two guages! I don't know as I believe one over the other just because it's more expensive. I'd try to resolve the difference in the instruments and not try and calibrate with the oil for now. I have a hard time believing that your OP is really out of spec.
 

TallPaul

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You mean maybe the bourdon tube in the cheap gauge was a 10 psi frictional drag? [LOL!] Yeah, that motorhome has parasitic drag issues to the tune of 7.5 mpg. [Mad] Confession: I got the Sun gauge at a garage sale [Embarrassed] for $2 and the Autogauge (by Autometer) in my pickup at a different garage sale for $2.50 [Embarrassed] . At least the Make Waves was store bought. Ok, lemme see, I think I saw a professional mechanics oil pressure gauge at JCWhitney. Guess it's time to do it right.
 
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This is a perfect illustration of the old saying: "A man with one watch always knows what time it is, but a man with two is never sure." [Smile]
 

TallPaul

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quote:
Originally posted by bulwnkl: This is a perfect illustration of the old saying: "A man with one watch always knows what time it is, but a man with two is never sure." [Smile]
[LOL!] Maybe I can come up with some sort of confidence interval. If gauge A says 60 and gauge B says 70, then probaby it is somewhere between 50 and 80. [Duh!] Or I could just break down and buy a decent gauge in the first place. Moderator: Given the turn this has taken, perhaps we ought to move this to either the Mechanical/Maintenance forum or the Auto Lubrication General forum. (And given my stubborn determination, I probably will try that 10w HDME trick anyway. Certainly the extra zddp won't hurt.)
 
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Well, seems to me that there is an oil pressure relief valve somewhere in there. Assuming it is set to the proper setting at the factory, and is in working order, it really shouldn't matter much if your $2 shows an extra 5 psi. Now, if it showed well below the recommended pressures, I'd be concerned.
 

TallPaul

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Good point Dick in Falls Church. The gauge does indicate that there is plenty of pressure. I am not at risk of oil starvation and the engine runs fine. So probably not to worry. Might just switch the Make Waves gauge into the pickup truck to see how it compares with the AutoGauge. Best setup would be a triple junction with all three gauges on the same engine. Hmmmm, maybe I can hook up my electric air compressor with such a fitting.
 

TallPaul

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quote:
Originally posted by bigpaulo: TallPaul, if you have to ask... [Smile] What's in your stash? Let's see if something you already own might be good for additizing your motorhome oil. I'm thinking perhaps a quart of M1 0W-20 if you have any.
I do have 5 qts Redline 5w20. Pretty expensive to run exclusively Redline though. I like the 10w HDMO idea better (besides, I get to buy more oil).
 

TallPaul

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Well you may be right blupupher. Anyway, I tried to check it with my electric air pump. I was very excited to find the pump fit right up the the gauge without an adapter. So excited in fact that I forgot to consider whether the pump exceeded the gauge--it did. Pegged the needle (this is the cheapo Make Waves gauge BTW) and when I cut the pump, it came back to about 50 psi. No problem, I took off the gauge face and muscled the needle back to zero. Ought to work really nice now, eh? [Big Grin] But the real solution came from bulwnkl's post on watches. I will simply forget about the first gauge's readings, and be satisfied with the Sun gauge. And I can ignore the numbers as all is relative. What really matters is if there is a dramatic change from the norm, not the actual reading.
 

TallPaul

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Ok, problem solved. Got a new Sunpro oil pressure gauge today and did a test run. Compare: Brand: Cold, Hot 2000 rpm, Hot Idle Make Waves: 75, 58, 30 Used Sunpro: 76, 70, 40 New Sunpro: 73, 61, 30 Looks like that used one is the culprit and the Make Waves was pretty decent after all--until I broke it. [Duh!]
 

TallPaul

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FWIW (or if anybody cares): I took the new Sunpro OP gauge and ran it in my pickup and got exactly the same pressure readings as my garage sale Autogauge (by Autometer). Then I took the used, suspect Sunpro and ran it against the Autogauge and it was only about 2.5 psi higher than the Autogauge. So why 10 psi higher in the motorhome? Only thing I can figure is that the run was 68 degrees and I drove avg 35 mph for the whole test and that just did not heat up the oil in that big 460 cid V8 like a good freeway run. So maybe I didn't have to buy the new Sunpro gauge, but I am glad I did as it verified all my gauges and is a much more readable dial (270 degree) for the motorhome than the used Sunpro (45 degree). And, since there is no gauge in the wife's Aerostar, but I tested it with the used Sunpro, now I can adjust the results and don't have to hook it up again. So that was my great anal oil pressure adventure [Freak] and I ended up with a broken cheapo gauge that actually had worked and a nice new gauge. All in all it worked out great. (Hmmm, wonder if I can hook the extra gauge to the lawnmower [Big Grin] ).
 
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TALLPAUL: After reading all of this I have decided that you, like most of us need a life, but I think we will make you PRESIDENT of the club. [Big Grin]
 

TallPaul

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quote:
Originally posted by Johnny: TALLPAUL: After reading all of this I have decided that you, like most of us need a life, but I think we will make you PRESIDENT of the club. [Big Grin]
[LOL!] Guess I am like the guy who wears both suspenders and a belt. Did I mention my oil stash hit a new high yesterday? 180 quarts! Oh yeah, this may qualify as the first thread where the thread starter has over half the posts. Yes, I sometimes talk to myself. [freaknout]
 
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