Guest bastaad525 Posted January 2, 2004 Share Posted January 2, 2004 Can someone PLEASE this for me? For a newly rebuilt motor that has already been broken in (like 3,000 on it already) is it better to run thin, thick, straight or multiweight oil? Right now I'm running Mobil 1 10-30, but I may switch back to Castrol non-syn for the time being until I can 100% get rid of some bad oil leak problems my motor has been having (and please dont ask me why a newly rebuilt motor is puking oil already... I really dont have a good answer for you guys other than "I FUGGED UP")... it's just too expensive to have to dump a quart in there every other day! Anyways, I was always under the impression that you wanted thin oil in new motors and thick oil in old motors, but lately I've been hearing a lot of contradictory arguments to this.... Stupid question here, would a thicker oil tend to leak more slowly? Not that I would run thicker oil JUST for that but it would be good to know... so what oils are better in what situations and why? Oh, I seem to remember someone mentioning this as a factor so I will too. I live in SoCal so it never really gets TOO cold here though lately we've actually had some real winter weather with lots of rain and temps in the 50's (heheh yep that's as real as winter gets around here), but never really any cold weather. Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted January 2, 2004 Share Posted January 2, 2004 Grumpyvette has stated several times that you want the thinest oil that will maintain 20-25psi (heres one http://www.hybridz.org/phpBB2/viewtopic.php?t=22767). That being said, I know for a fact that 30W leaks slower than 10W-30, and I have heard that 90W leaks even slower. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted January 3, 2004 Share Posted January 3, 2004 If you built it, then you know your bearing clearances. Tight clearances are fine with thinner oils, but when you get up around .002-.0025 or better then I'd run a heavier one. (Journal diameter also comes into play- I'm thinking in terms of big American iron). Mobil1 is a great oil, but I couldn't afford to toss it through a seive; you really should consider fixing the leak(s). I think Mobil1 has an almost constant viscosity (like a deisel injector calibrating oil) & I've heard that it tends to find any small holes and escape. In your area you could probably run 20-50, even in the winter time. Straight 30 might get a bit hard to crank on cold mornings. 15-40 (do they make 15-50?) if you don't want to bet on warm mornings. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted January 3, 2004 Share Posted January 3, 2004 Yeah well the problem is I dont trust the stock oil pressure sender or gauge for squat so I'm not really gonna go by that. The thing doesn't even work half the time, and it's not high on my 'to fix' list. But it does sound like I am running too thin of an oil, for sure. I'm not 100% positive but I'm willing to be my clearances arent as tight as they could be And now that that little fact makes thicker oil make more sense, I'll gladly take the added advantage of slower leaking. I've already figured out the problem as far as the leak goes, it WAS both the main seals and oil pan gasket, which I had all three replaced. Then the oil pan gasket promptly started to leak again... turns out the oil pan is warped. I should have a new one in by next week. In the meantime I'm gonna start throwing Castrol in there. I really only wanted the Mobil for protection of the turbo itself, but I'm really good about idling down after driving and such, so a few hundred miles of Castrol shouldn't hurt. Okay but I am unsure of one thing, if I WERE to go by the oil pressure, lets say my pressure at idle is too low, would I want thicker or thinner oil to remedy this? Quote Link to comment Share on other sites More sharing options...
JKDGabe Posted January 3, 2004 Share Posted January 3, 2004 Thicker will give more resistance to flow thus creating pressure. But resistance means less flow thus less lubrication. On one of my old cars I had to use 2 q's of 10w-30 and 2 of 30w. That way it didn't use it as fast but still didn't clank/rattle when I started it on a cold morning. Quote Link to comment Share on other sites More sharing options...
fl327 Posted January 3, 2004 Share Posted January 3, 2004 Ive found on my car when the guages are working right, they read kinda high, and when the sender leads are dirty or going out, they read low. I run 10-30w synthetic and 2 10-30w non synthetic. Works good and made a small leak I had a miniscule one. Yes I know, its better to run synthetic fully, but I change my oil what seems like once a month sometimes, so when I buy a 6pack of synthetic, it lasts two changes. Just me. These turbo cars are the only cars Ive ever driven that felt like they get faster with an oil change, makes sense it would though. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted January 3, 2004 Share Posted January 3, 2004 I'd find where it is leaking from and duct tape a cat litter box under the car right there to catch the oil. Then you can take the cat box and dump the oil back into the engine. This should save you some money, and be nicer to the environment. Just make sure you get yourself a clean cat pan, and check for cats before you start up the car in the morning! If you dont trust your oil pressure gauge, and you know your engine is leaking oil that bad, I would really recommend against driving it. That is just too much to risk. If you put in thicker oil, you might cause it to build up more pressure and spring a leak somewhere else. I HOPE you are exagerating when you say a quart every other day. If you are leaking that bad, I'll bet there are parts of the engine that arent even getting lubed. Quote Link to comment Share on other sites More sharing options...
fl327 Posted January 3, 2004 Share Posted January 3, 2004 I'd find where it is leaking from and duct tape a cat litter box under the car right there to catch the oil. Then you can take the cat box and dump the oil back into the engine. This should save you some money' date=' and be nicer to the environment. Just make sure you get yourself a clean cat pan, and check for cats before you start up the car in the morning! If you dont trust your oil pressure gauge, and you know your engine is leaking oil that bad, I would really recommend against driving it. That is just too much to risk. If you put in thicker oil, you might cause it to build up more pressure and spring a leak somewhere else. I HOPE you are exagerating when you say a quart every other day. If you are leaking that bad, I'll bet there are parts of the engine that arent even getting lubed.[/quote'] Strongly agree. Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted January 3, 2004 Share Posted January 3, 2004 If your using a quart every 2 days something is really wrong and a leak like that should be easily found. If your not seeing it under the car then its going somewhere. Id check it out before your new rebuild goes south. On another note, if your using fram filters since we are talking about oil, dont go there they SUCK!!!!! Quote Link to comment Share on other sites More sharing options...
fl327 Posted January 3, 2004 Share Posted January 3, 2004 Maybe some of the bolts are loose? Even if its warped, unless its extremely warped, it should seal pretty good, I can imagine a little leak, but man that pan has like 40 small bolts holding it on!! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted January 9, 2004 Share Posted January 9, 2004 I checked and double checked all the bolts and they are pretty tight, was carefull not to overtorque them this time though. It's definately leaking oil from between the pan and the block itself, this is after installing a new gasket. It is a bad leak.... I overstated my first estimate though... it will lose roughly 1/2 a quart after about 50-60 miles of driving... still a bad leak, and yes i have stopped driving the car until I get another pan and gasket installed, hoping this sunday. Both because I am worried about not getting enough oil circulation, and partially because the oil is leaking onto the crossmember, and from there getting blown onto the exhaust downpipe, creating a very very bad smell in the car. Quote Link to comment Share on other sites More sharing options...
fl327 Posted January 9, 2004 Share Posted January 9, 2004 I can imagine it stinks really bad. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted January 9, 2004 Share Posted January 9, 2004 yeah for a while I didn't realize there was oil leaking... and I was panicking because I couldn't figure out for the life of me, why the exhaust smell inside of the car had suddenly come back, when it had been all but gone for well over a month. Then, not only did it come back, but got rapidly worse. I had the local muffler place throw the car up on a hoist a few times, looking for newly developed exhaust leaks... and no one saw any oil splatter on the exhaust at that time. But last week I went poking around with a flashlight and there was a HUGE splatter all over the dp... even better was the bit cloud of smoke that came wafting out of the engine bay when I popped the hood. I'd love to say it was a relief to finally figure out the cause of all these problems... except for the fact that changing a pan and gasket on this car happens to be such a pain in the ass! Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted January 9, 2004 Share Posted January 9, 2004 I broke in my engine with mineral oil 10w30 castrol..just like Nissan puts in from the factory. I was recommended by my engine builder/racer to run 20W50 syn, and that is what I am running now.... The 50 is the cold, and the 20 is the hot rating (99% certain) He said that is what he runs in all of his Z engines that he races with. We have cold weather here, and that is too thick, but my car is not on the road in winter anyways, so I'm quite satisfied with it so far... My pressure doesn't spike through the roof when cold... Runs about 3/4 on my stock guage, and 1/2 at idle... My .02 cents Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 10, 2004 Share Posted January 10, 2004 One quick point, oil pumps are positive displacement pumps, meaning they pump the same volume of oil for a particular engine speed regardless of the discharge pressure. Thus thick oil will be harder to pump and generate higher oil pressures, but the flow volume will be the same either way. Another quick questions. I see a lot of posts saying things like Fram and Purolator oil filters suck. What is wrong with them? I know a lot of people think an oil filter has to have an internal check valve, which the cheapest Fram filters don't, but their "tough guard" units have a check valve and a pretty good filter rating. I use the Fram tough guard filters on both my vehicles. Am I hurting anything with that? Quote Link to comment Share on other sites More sharing options...
johnc Posted January 10, 2004 Share Posted January 10, 2004 Grumpvette is right, you need about 25psi at each rod bearing journal at max rpm (which matches up with what Jim Thompsopn told me). Unfortunately, most of us have no way of measuring oil pressure at the bearing journals so we have to overpressure the oiling system. An old rule of thumb is 10 psi for each 1,000 rpm and that's a good rule for a street engine. L6 engines don't need a lot of oil pressure because they have a very well designed oiling system. Regarding oil viscocity for a street engine, 10W-30 or 10W-40 is plenty. Anythign more is just using horsepower. Racing engines that put a lot more heat into the oil will run a 20W-50 or a striaght 50W. Also remember that multigrade oils have as their base oil the lower of the viscosity numbers and then an additive package is mixed in that thickens the oil to the higher number as the oil heats up. For example: 10W-40 oil is made from 10 weight base stock. The additive package includes long chain polymer molecules that unravel as they are heated up. This unraveling causes the viscocity of the oil to increase. So, a straight 40W oil is thicker in the can then a 10W-40. At normal operating temps the 40W is still a 40W oil while the 10W-40 might be at 32W. The marketing term "oil breakdown" refers to the multi-grade oil's additive package being dilluted or affected by contaminates to the point that the long chain polymers come apart and the oil viscocity remains at some static number. A straight weight oil retains viscocity although it might still be contaminated to the degree that its not able to maintain a good wedge on the bearing surfaces. Quote Link to comment Share on other sites More sharing options...
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