Okay, so I'm needing some input as to what weight oil to run in my new build. Block is an aluminum LH6 5.3. Right now, I'm still on Driven 5W30 break in oil, changed it after 500 miles and plan to run another 500 on this batch before switching to whatever I'll be running. I've got a Melling 10296 High Volume pump with the standard pressure spring in it. This is the first engine I've built with bigger clearances for boost ( .0022-0023 rods, .0027 mains - thrust is .0030 ), and my oil pressure varies a LOT cold to hot. When I start up cold, I'm at 65-70 PSI at 850 RPM idle. Just trying to move around, oil pressure is spiking to 75-85 between 1200-1500 RPM. Once the engine is hot and I've been leaning on it, however, idle pressure drops to around 25-30 and at high RPM ( I hit 7500 regularly ), it's only around 55PSI. I'd like to see it closer to 70-75 at high RPM. Idle pressure isn't that concerning, as my SBE LS3 in my Camaro idles around that pressure. I know the aluminum blocks grow more with heat, which is probably a big part of why my pressure drops, but I want a safer amount of oil pressure at high boost/high RPM.

I'm assuming a heavier weight oil will help, and I was considering going to a 10W30, but I'm concerned that cold idle oil pressure could be enough to blow out my seals. Or am I overthinking it? Is my engine going to live at 7500 and 20 PSI of boost with 55 PSI of oil pressure? This is my first boosted engine build and I want to make sure it lives.

 

It sounds to me like you should have the high volume oil pump.

Thicker oil can band-aid it, but at 55 pounds and that much RPM it's less than optimal.

 

Put regular oil in it and see where it is. Ive found the driven br stuff tends to run low psi

 

Ok. 10w30 is not thicker than 5w30. They are both a 30w oil. The 5 and the 10 prefix before the W are indicative of how the oil behaves at 32 degrees Fahrenheit. The 55psi at big RPM is a little low to me personally…I’d like to see 60+. Here’s the tricky thing about the issue here…oil pressure doesn’t lubricate an engine. Oil flow lubricates (and cools) an engine. Moving to a 40w oil (which is a thicker oil than 30w) will increase your hot pressure readings, but will not flow as well a a 30w oil. It’s not dramatically thicker…and could very well be the answer here, it’s just a matter of testing to figure this out. What oil filter are you running? I switched from a Wix 57060 to a 57502XS and lost 10psi on my 434, just from a larger filter area. Have you cut your filters open to check for debris?

 

@Kawboom I am running the 10296 Melling, which is high volume. I know the prefix designation is cold flow, but I've read that the closer you are between cold and hot designations, the more stable the oil is. Which was why I wanted to try 10W30. And in my experience years back ( which I'm sure is no longer valid ) 10W30 raised my oil pressure when switching from 5W30, but we're talking 25+ years ago. I know my clearances are why my pressure is lower hot ( less resistance to flow ), but like you stated Che70velle, I'd also like to see 60 PSI+. I had some minor break in "glitter" on my first oil change, but I drained my oil through a paint strainer and didn't catch anything. Filter looked good as well, nothing more than some initial "wear-in" material. I'm running a Wix filter as well, not sure the part number. However, the oil pan I have is an F-body pan that came on an LS3 crate engine, and when I bought a filter for my '98, it didn't fit. Turns out, they changed the filter mount/inlet to a larger diameter, which necessitated a different filter. I doubt that would be enough to lower oil pressure, though. Also, I am not running an oil cooler, and it's possible my oil is getting too hot. I only see those low pressures when I've been getting on it pretty hard and my coolant temps are 200+. Engine really seems to be solid, I haven't lost any pressure cold or hot. The numbers I posted are pretty consistent from first start up to present, which is about 900 miles worth of driving, none of it easy.

 

That is correct: at some point around maybe 07 or so, "they" changed from a filter w SAE threads, to one with metric threads. The size isn't really all that different; it's like, ¾" SAE vs 19mm metric, or some such. As close to equivalent as it comes. Just, incompatible. The thing that changed wasn't "the pan" though, it was the adapter screwed into the pan; which DOES interchange. I.e. you can take either adapter and screw it into any pan to use the filter thread you want if that's a thing. For whyever, all the newer oil pans, including replacement ones for older engines, seem to come with the metric adapter in them, so you have to use the newer filter unless you change it out.

As Che70 points out, different filters can result in different oil pressure, depending on how well they flow. In general a more "effective" filter (better at trapping small particles) will necessarily flow more poorly and result in a greater pressure drop. I kinda think the Wix filter is one of the "better" ones as far as filtration, meaning it's likely to cause lower oil pressure. Filter choice in that sense is a compromise between effective filtration and unrestricted flow. There's no "best" choice in that regard although of course there are crappy filters and there are higher quality ones, it's more how you see your priorities as being ordered.

Thicker oil will obviously also increase the pressure drop in the filter.

Personally I think it's VERY POOR policy to run thicker oil just to make the gauge read higher. Precisely as he also stated: the engine need FLOW through the bearings, not PRESSURE. All that the pressure does, is create flow. You could probably literally put gear lube or candle wax in your motor and get HUNDREDS of psi; I doubt your bearings would like that very much though.

 

15w-50 Mobil 1, Maxima or Joe Gibbs green stuff. Same weight.

 

Well, if flow through the bearings is the important consideration, I believe I have that covered by using the high volume pump with increased bearing clearances. But that doesn't address the oil pressure. Is it adequate? I've always subscribed to the 10 PSI per 1000 RPM train of thought. I'm simply wondering if an oil change ( and I'm open to ANY viscosity / brand ) will be enough to gain that extra 5-10 PSI. I also want adequate filtration, which is why I run WIX filters as well. However, is having a more effective filter worth the pressure trade off? If not, what would be the recommended fix? I used the supplied pressure spring in the pump, I could swap to the higher pressure spring ( although that's a lot of work I'd rather not do ). Is it possible I simply am getting the oil too hot and need to install a cooler?

 

Depends. That's a choice YOU get to make, based on YOUR specific circumstances.

It's a law of physics. You want more flow, you gotta relieve restrictions. It's just that simple. Don't overthink it because "car"; it's STILL just a law of physics.

Personally, I'd suggest taking a look at the filter specs, and seeing if the impurities you expect to need to remove from your oil, are covered by a less restrictive filter. For example, if it removes (I'm just making up #s here, don't blame me if they don't match anything) 95% of all particles 2 microns or larger and 99% of all particles 5 microns or larger, and all the impurities you expect (dirt, debris, etc.) are 10 microns in diameter, then does the filter's performance at 2 microns REALLY justify accepting the restriction that the filter medium with smaller pores or more layers imposes? IOW, since it's all a game of NUMBERS, use NUMBERS to help you figure it out. FWIW, most metal debris particles are MUCH larger than most "dirt"; that's why people use screen filters for pure racing applications, is because even though they're not a particularly "effective" filter, they're all that's needed; if you keep the engine clean, like having a properly functional PCV system rather than breathers, you won't be getting much "dirt" in it ANYWAY. Or, if the only place you run the car is at the track, and it only drives 2 miles a weekend in the process, then how much "dirt" is it ever going to pick up, anyway? Think about stuff like that instead of just "big numbers on the gauge" eye candy and "most effective filter" even though it's not necessary (won't ever have small enough particles around that it needs to catch in the first place).

I'm reminded of the Super Stock guys back in the day (maybe they still do this way, I haven't been around that for a really long time) that used the LOWEST oil pressure and the thinnest oil they possibly could and their engine still survive for the teardown interval they're going to be following ANYWAY, because higher psi and thicker oil just waste engine power, if it's not really needed. The motor will make more power without the extra burden.

Seeing nice big psi #s on your gauge isn't worth a crap if the bearings are starved for oil flow. Which of course is the YYYYYYYUUUUUUUUUUUJJJJJJJJJJE problem with the old "10 psi per 1000" oversimplification. Yeah sure, you might be seeing a nice pretty 60 psi on your gauge at 6000, butt if there's no oil FLOWING through the bearings, then you're STILL not lubing them adequately. Just making random changes in whatever way just to make the gauge show big #s isn't some kind of rational approach.

 

What’s your compression set at? Compression makes heat. At the end of the day here, it could be that your gauge is mis-reading or the sender is a few degrees off. I wouldn’t do a tear down to look for 5psi unless this is an endurance build and I’ve got external oil pump data telling me something is wrong. You’ve got enough bearing clearance for 40w oil here…maybe consider trying it to see where it puts you. Lots of guys run 40w in their LS engines. If you decide to stay 30w, don’t fret over 55psi…you’ll likely be just fine.

 

I'm running 10.5:1 compression, as I built the engine to run on E85 from the start. So it's definitely getting some heat in it. Most of my observations of lower oil pressures were on hot days ( 85* + ) and either extended low speed driving ( cruise nights / car shows ) or after doing street pulls. With the clearances I have, I don't feel the pressures I have observed are anywhere near the danger zone, but just from past experience I was concerned. I'm putting it up for the winter this weekend, I'll switch over to a non-break in oil in the spring and look into my filter specs to see if I may want to try something different. I'm running a stock Gen IV oil pressure sender going to the Holley, and using a Gen III sender at the front of the block near the pump going to my gauge cluster. That one reads higher for obvious reasons. Thanks for all the input, gives me some things to ponder over winter.

 

I picked up 7 psi at idle switching from the Mobil 1 5w30 to 5W40 Shell Rotella T6. Totally stock engine. I was getting 30 or so at idle, 50 at redline. I did the oil pickup brace and changed the O-ring, accomplished nothing. Swapped to T6 5W40 and immediately saw 37 idle and 60+ at 5500rpm. I’ve been running like that for 12k miles and it’s a happy ol’ truck. Just my $0.02

 

Have you tried a Wix XP filter?

 

And the BENEFIT of that downgrade , was ,,, ... ?? That is, the fact that the vehicle has simply "survived" for a few months in spite of it, no matter what influence you had on the gauge, is HARDLY any "proof" that the change "improved" anything.

 

I have not, but I will look into it. I know there are also some part numbers that fit which are longer, and it may be possible that having a larger amount of surface area in the filter media could result in less of a pressure drop.

 

Yes indeed.

The ones in trucks are longer than the F body ones. Not sure if that's A Good Idea, since the filter may hang down below your oil pan, and thus be highly vulnerable to road damage; butt worth looking into especially if that's not a concern (pure race / no street for example).

 

I have a Quicktime bellhousing that drops about an inch and a half below the bottom of my oil pan - if I hit something that could take out a long filter, I'm really going to know it, lol. Plus, my K-member is also lower than my pan ( although not as much as the bellhousing ), so I think I'd be fine. I don't drive it all that much, it's just a toy.

 

So, for the halibut, I decided to see what The Google had on offer. I was hoping to find somebody's full listing of thread, dia, height, and microns, butt... no.

Here's what I could get from Mahle. Maybe you could cross-reference their part #s to whoever else and find the same physical size, then try to track down the micron ratings. They offer abuncha other threads besides these 2 butt those would be useless to us. Note that there are several part #s with the same external dimensions in some sizes; I would suspect that those have different micron ratings, especially since they're in several of the most popular sizes. I believe the stock F body filter is 3" x 3.4" more or less; some of the 6.0 trucks, and maybe the 6.2 ones, use a longer filter, like maybe 4.65". Iunno, didn't go drilling into it that deep.



Bottom line to me though, is how to get the most possible oil to/through the bearings. Artificially forcing the gauge read a higher # is useless if it doesn't result in more oil getting to the bearings. Since our oil pumps are essentially a constant-volume type, i.e. they move x amount of oil per rev regardless of anything else (and of course if some of that is air from a bad pickup O-ring, then that portion of the volume is NOT oil), and the pressure just ends up being whatever it happens to be based on how rapidly the pressurized oil can pass through the restriction of the filter, flow down the passages, and escape through all the clearances. The high limit to the pressure is the relief in the pump; so for example, if your relief spring is set to 65 psi, and there's 10 psi of pressure drop in your filter with your choice of oil, then the gauge will only read 55 BEST CASE, even though the pump is maxing itself out. This is where filter choice comes in; enough filter to keep the oil clean "enough", butt not SO MUCH that impedes the flow (and reduces the pressure in the whole rest of the system that comes after it). It would be possible to have VERY high pressure butt STILL have the bearings starve for oil, if the oil can't flow through the clearances adequately; and conversely, to have EXCELLENT lubrication at lower pressures, if the bearings are liberally bathed in oil and their surfaces kept from ever touching each other. Personally I'd prefer to err toward the latter condition; just jamming the gauge to a high number by using thick oil doesn't pass the smell test that way. OTOH the "ideal" viscosity is going to be based on clearances, expected contamination (a blown alcohol motor for example will almost certainly need thicker oil than a N/A gas one), oil change interval, filtration needs, and so on. Not to mention, YOUR own personal preference as to what order of priority all of those concerns are in, to YOU.