Oil pressure vs oil level

[summit1]

Searched archive and couldn't find what I wanted. Any feedback is appreciated.<br /><br />2 things:<br />1- changed oil last night and noticed only 4 quarts came out. 4.3 holds 5, and I did not pump oil out, I used drain plug w/fitted drain hose from bilge. The oil pressure has always been in normal operating range. I did not check oil level last time I went out (I usually check it, but this motor has never used much if any at all), but I do watch pressure, and it has always been in acceptable range. Question-Was it ok if level a little low (I know not ideal), even though the oil pressure was there?<br /><br />2- This motor has always had oil specified by merc manual in it until mid-season oil change this year...I put HDDO rotella 15w-40 in, and I was a quart low last night. I have never had an oil consumption problem, and I only had 40 hrs on this oil change. I pulled a few plugs and they had a little black film from the oil, not too bad though. I am going with Penzoil HD-40wt now. Question- could the oil I used be the cause of the consumption, and can using recommended oil wt help reduce or eliminate it?

 

[tommays]

Re: Oil pressure vs oil level

any motor has a high and low range for oil level in you case i think the most that may have happened is that the oil would be at a higher temp because there was less of it to heat up<br /><br />it should not affect pressure unless it reaches a much higher temp or the oil pump starts to draw air if its very low<br /><br />only time will tell when you switch to 40wt i think it would be less likely to use a much with a st grade but i dont want to start a nother round about the correct oil <br /><br /><br />tommays

 

[Buttanic]

Re: Oil pressure vs oil level

If you were using a straight 40 wt before the 15-40 than I would say it is possible that that the 15-40 is the culprit. The oil is picked up by the pump at a level of less than 1 inch above the bottom of the oil pan. The pan would have to be almost empty before a loss of oil pressure would be noticable. One quart low would be about at the add mark on the dip stick and should not cause any problems.

 

[DayCruiser]

Re: Oil pressure vs oil level

I pull the dipstick out and wipe it off and then stick it in and get one reading. Repeat and get an entirely different reading. The first one is usually shows a quart down and the second one shows full.<br />Kinda confusing which one to go by

 

[98LarsonGM57]

Re: Oil pressure vs oil level

Last spring my 5.7 volvo was overfilled by about a quart - when ever I ran over 4k rpms my oilpressure would begin to drop off - as soon as I would pull the throttle back even 50rpms it would would jump right back up to normal... After draining a quart out it has run normal all summer. I assume the oil was getting slapped into a nice lather at high rpms.. <br /><br />Not sure it has anything to do with your problem -but a lesson learned none the less. <br /><br />Good Luck, <br /><br />Lee

 

[Bondo]

Re: Oil pressure vs oil level

Ayah,<br />A Quart low is Better than a Quart Too Much.............

 

[summit1]

Re: Oil pressure vs oil level

Thanks for all the info and advice!

 

[achris]

Re: Oil pressure vs oil level

I pull the dipstick out and wipe it off and then stick it in and get one reading. Repeat and get an entirely different reading. The first one is usually shows a quart down and the second one shows full.<br />Kinda confusing which one to go by

Mercruiser engines have the dip tube run all the way to the bottom of the sump pan. The reason is so the oil can be pumped out if the plug is not accessible. (I had a rust hole in mine a few years ago and had to cut the bottom off and weld a new section on. Haven't had a sump plug since.) The explaination for the different dip levels goes something like this :<br /><br />Because the tube goes all the way to the bottom, and the top of the stick has a rubber seal on it, the air in the tube (above the oil level) is trapped and, being subject to the heating and cooling from use of the engine, changes it's volume, in accordance with Charles Law . This will draw oil up the tube as it cools and push it down as it warms. If the air gets warm enough it will expand to the point where it will bubble out the bottom of the tube, thus changing the amount of air now trapped so when it cools again the level will be different. Also be aware that as you push the stick down and seal the top of the tube you will also be pushing the oil down.<br /><br />I usually wait a couple of minutes after pulling the stick, so the oil level can stabilizer, before dipping.<br /><br />Chris............

 

[deputydawg]

Re: Oil pressure vs oil level

Oil pressure is measured at how much pressure the pump is pumping into the sender. In order for there to be low enough oil to change pressure, you need to lose volume in the system. A quart low won't cause a drop in pressure. As said here it might cause extra heat thinning the oil. You should be able to run 2 quarts low before any damage occurs, although never do this if it can be avoided. I have been in engines that have run with only 1 quart in them that have no permanant damage, but marine engines run at constant higher rpm's so again never do this. Answer to first part of question, don't worry about running it a quart low. You didn't hurt anything.

 

[LubeDude]

Re: Oil pressure vs oil level

Originally posted by summit1:<br /> I pulled a few plugs and they had a little black film from the oil, not too bad though.

I doubt it was from the oil you were using, If you were not going to use the mercruser oil anyway, the rotella oil was a better oil than the Pennzoil, But the Pennzoil you chose is still ok to use. IMHO.

 

[summit1]

Re: Oil pressure vs oil level

I wasn't sure about the rotella. I have never had an oil film on the plugs, and I changed them out at the beginning of the seaon and ended with film the on them the other night. I have never had to add oil between changes, and now I come up a quart low...it just puzzed me how that happened all of a sudden. I am not blaming rotella, as there are too many people to count that love the stuff (including dad.) I wondered if it might have happened from changing types of oils or something.

 

[Peter J Fraser]

Re: Oil pressure vs oil level

achris has the answer on the variation in your oil levels. Use the second dip as correct as he says.<br />It is a common situation to find.<br /><br />Peter

 

[KaGee]

Re: Oil pressure vs oil level

Summit,<br />If this is the first time this has happened, don't get so excited. Check your level and plugs mid change next season. I you have a problem... it will show up.

 

[Boatist]

Re: Oil pressure vs oil level

Summit 1<br />I think the type of oil un use can make a big difference in the amount of oil you burn. To start with 15-40 is much thinner oil than straight 30 unless your engine is running very hot. Thinner oil does leak out eaiser and get by rings and valve seals to be burned eaiser.<br /><br />Straight 40 weight oil is too thick for your engine. Check your manual and I think it will say to use straight 30 weight. Straight 40 if more for engines running in the 200 to 250 degree range or engine with very high wear. For a winter time oil just not the right choice in my opinion.

 

[summit1]

Re: Oil pressure vs oil level

I am not going to use the boat this winter. 100* outside temperatures are not strangers to us here in Texas (in the summer), which is why I went with the 40wt. Usually though, the temps are in the mid to upper 90's in summer.<br /><br />Is there anyone else that has gone the 40wt route?