Oil suggestions for a rather unique vehicle...

[facelessnumber]

Hi, y'all. Great board you have here. I've been reading it a good bit, searching, and learning more about oil than most people ever care to know. But there are a lot of factors for deciding on an oil for this particular application, and I feel like I could greatly benefit from some real expert advice on this.

What I've got is a '91 all-wheel-drive Olds Bravada. I've put a rebuilt early block 4 bolt 350 V8 in it, with a moderately high-lift, flat-tappet hydraulic cam. Standard stock replacement oil pump. It's carbureted of course, so no O2 sensors to be concerned about, and there are no catalytic converters. A very old-school setup.

Here's where it gets unusual... Some alterations had to be made in order to fit that engine into this truck. To clear the front axle and differential, it required a notched oil pan. It's a deep-sump pan, a bit wider than stock. Due to the front driveshaft being in the way, I also had to install a remote oil filter kit. Because the headers are run the way they are I also installed a large oil cooler. There's not much room and my radiator needs all the air it can get, so I had to put the oil cooler under the hood with a 9" electric fan on it, so I'm sure that cooler isn't performing as well as it could.

When I first put this together it was during summer in Mississippi. I quickly discovered I had cooling issues, so I installed a Corvette radiator, but I don't have room for a large fan, so in sustained heavy traffic the coolant occasionally still gets hotter than I'd like it to. About 225. But on the highway and in milder weather (like now) it runs at a steady 190.

My concern is oil pressure, heat, and lifter noise. These problems don't come into play until the engine is hot, but as long as I don't get on the highway there are no problems. I finally discovered after replacing too many starters, that my headers were to blame. They were burning my starter (which is now heavily shielded) and they're heating my oil at sustained cruising speeds. Exhaust is too close to the oil pan and I'm pretty sure there's nothing I can do about that.

I'll start the engine up and the pressure will be a nice and healthy 40-60 PSI. At operating temperature I'll idle at about 500 RPMs with just under 10 PSI, and run with literally just over 10 lbs for every 1000 RPMs. This acceptable from what I've read, and to be expected since my oil has to travel through six feet of 1/2" hose, a remote filter and an oil cooler, and I'm using the pressure tap on top of the engine behind the distributor. At this point there is no lifter noise. But after I've run it on the highway for a while and the oil heats up from the headers, my idle pressure is just barely above the peg and I can hear my lifters clicking. Cruising pressure at 2000 RPMs is about 20 lbs.

I'm not going to ignore the idea that it could be bearing tolerances, but I think my problem is heat. I started off with Advance Auto's store brand 10w30, and the heat made that stuff useless even faster than with their 20w50 that I'm running now.

I'm told that synthetics can handle high temperatures a lot better than conventional oils. I started to buy a bunch of Castrol Syntec, but then I read that it's not technically a synthetic and is petroleum-based. Some people have told me that a thicker oil will raise my oil pressure, while others say that I need a thinner oil because of my remote filter, hoses and cooler.

I'm looking for a reccomendation on a good oil that I can find locally, which will stand up to extreme heat, keep the pressure up, and tolerate the occational weekend drag race or autocross. Winter is a non-issue here. About 30 F is as bad as it gets. I was considering Castrol Syntec or Mobil 1 Truck/SUV.

Another consideration is, I've got an 8-quart pan and probably at least 2 quarts in the filter, hoses and cooler. I'm reluctant to spend $6 a quart with that kind of capacity, but if that's what it takes I'll do it...

Sorry this message got so long, and thanks for your help!

Again, excellent site you have here.

 

[KJA426]

If it doesn't get too cold then an SAE 30 or 40 or even a 20w-50. The high mileage series of oils may work also for you.

 

[Warstud]

I wouldn't use SAE XX in a automobile especially under 40 degrees plus they don't have detergants in them. If your having oil temp. issues you want to go thinner and yes a synthetic will help but may not be the cure all your looking for.

 

[KJA426]

The SL rated SAE 30s have detergents. There has always been non-detergent 30 out there though.

 

[marco246]

Hi, FN,

I'd agree with you that you ought to move to a fully synthetic oil to cope with the high temperatures your mill is generating. The big question, even more important than the brand, is what viscosity? You're already running a 20W-50 and I take it are unhappy with the lifter noise and perhaps the oil pressure. 20 psi @2000 rpm while cruising might meet some arcane rule of engine math, but it seems low to me. (But I am used to non-U.S. engines which typically run higher numbers).

So I think you're going to have to experiment. I'd recommend working in the 40-weight range first. Some good oils to consider are (as you mentioned) M1 T&SUV 5W-40 and Shell Rotella T 5W-40. The latter is normally associated with diesel usage but is SL rated for cars and is quite robust. These oils will stand up to the heat and will probably circulate more readily than the 50 weights, possibly bringing the oil temperature down a bit. Although it seems counterintuitive, a lighter weight oil might provide higher oil pressure in this case.

It may well be that a 30 weight will prove better in your application, or that you will ultimately head back to a 50 or even a 60 in a synthetic.

Whatever you choose, will you please keep us posted as to your progress?

Cheers, Mark

 

[JHZR2]

m1 5w-40 is about your best bet... Id use that if possible.

JMH

 

[JTK]

Why not just wrap the headers and be done with it? Fuel dillution from that carb'd beast may cause you to have to dump $ synthetics early.

Joel

 

[facelessnumber]

An interesting array of responses... So, what I'm getting here is that I should continue using a relatively thick oil, but perhaps not as thick as what I'm at now, and go synthetic. And I'm seeing suggestions of something like 5w40 or straight 30 or 40. Am I right to assume that single-weight oils stand up better to the heat, but the concern with their use is winter and cold starts?

Based on what y'all have said so far, I think I'll first try a synthetic 5w40. (I'm surprised to hear Rotella T suggested. I had no idea that was synthetic, and it's pretty cheap!)

After the winter is over, when I'll be seeing more intense heat, should I continue the 5w40 (or whatever weight ends up working) or is a single-weight 40 or 30 going to be more resistant to the heat?

Thanks guys! Very helpful.

 

[chuck wood]

The single weight 30 or 40 would be a waste of your time compared to a fleet duty synthetic 5W-40 for year-round use.

 

[facelessnumber]

Good question, JTK. I have been battling with that idea for months, and, if I can't find an oil that can deal with the temperature, that will be my next step.

The reason I haven't wrapped my headers yet is twofold. One, wrap kills headers quick. Wrapped headers will last two years at best, and with the humid climate here, I'm afraid they'd be rusted through in a matter of months. I probably should have bought ceramic coated headers in the first place, but we live and learn...

Second reason is related to the first: When I do eventually change my headers, the engine's going to have to come out in order to get to all the bolts. I've moved to an apartment complex since building this truck, so pulling the engine again will be a major operation. I'll do it if I have to, but it's my last option.

Every time I turn a wrench on this truck it reminds me that neither the good Lord nor General Motors ever intended this slobbering beast to be shoehorned into this little truck. Some things that should be simple can get complicated. But is it worth it? Oh, yeah. All I have to is hit the gas at a light or in a sharp turn, and I'm reminded why I put myself through all this.

Now, my wife on the other hand... She is not yet convinced. =)

 

[BubbaP]

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The single weight 30 or 40 would be a waste of your time compared to a fleet duty synthetic 5W-40 for year-round use.

I agree- Rotella 5w40.

 

[Propflux01]

One problem is you are trying to cure the symptoms rather than the problem. your situation, if your lifters are knockin' after it gets warm, there are two possibilities taht come to mind, one, you are just plain too hot. two, your remote set-up is somehow preventing flow through the engine.Most remote setups (I.E. relocated filters) usually have an adapter that starts at the old filter location and ENDS there too, rather than in teh back of the engine. This is leading me to think your bypass is stuck open, only minimalising your pressure, and what little oil is bypassed and going to the filter, then to the back of the engine (tapped,I presume into the cam/lifter oil gallery)is just not enough to keep teh faster-rotating cam/lifter setup oiled. therefore causing both your noise and some added heat to friction. I would replumb that oil return back into the filter adapter instead of the back of the block. I think this, and checking your bypass will at least help, if not cure your problem ( short of some really bad-worn cam bearings)...

 

[t-squared]

Faceless, is it possible that oil foaming could be causing your pressure problems? With your non-stock pan shape, make sure the crank throws don't swing down into the oil as it makes its way back to the deeper part of the pan.

 

[facelessnumber]

Thanks, Tim. I should clarify what I meant when I mentioned the pressure tap at the back of the engine. My remote kit does start and end at the stock filter mounting location. I was referring to the tap that I used to install my pressure gauge. SBC's also have a pressure tap at the bottom of the engine, down by the filter, which is often used for an oil pressure gauge. I suspect that this location probably yields higher pressure readings, and I'm thinking about installing a second gauge down there or moving the one I've got.

The tap at the back is where the stock sending unit was installed on the factory 4.3 V6, and that was the only factor I used in deciding where to plumb for my gauge.

It's entirely possible that I'm comparing apples to oranges and that the tap I'm using is just intended for an "idiot light" like the way it was original configuration. My pressure readings may be artificially low. I really have no idea about that... I have no formal training and I'm absolutely not a mechanic in the least. I'm just technically-minded and not afraid to bastardize a car. =)

I believe, and I really hope, that heat is the primary problem. The lifter noise only happens at idle once I've been on the highway for a while. I'll report my results when I get a chance to replace my oil with the 5w40 Rotella. Thanks again, guys.

 

[Curious Kid]

How about installing a high flow oil pump in place of the OEM unit? This will help keep the flow and thus maintain higher pressure while still enabling you to use a weight of oil that isn't loaded with viscosity modifiers. The added flow will also help with removing heat, and going one step further would be to add thermostatically controlled oil cooler...or did I miss that in your post?

Like others have said, make sure the pressure controlling bypass valve isn't stuck open.

You may want to keep an eye on underhood temps to minimize the risk of fire.

Good luck.

 

[drk]

I think the poster would be better off adressing the cooling issue. utilizing a system that will better keep the coolant temps down and improve his currant oil cooler setup. I think having the oil cooler under the hood is just heat soaking the system. any thoughts on relocating it or altering the hood to move more air through the engine compartment?

 

[tnt31]

Shell Rotella T is not all syn. The have regular Dino also. If you want the syn get the 5w-40 in the blue bottle. My local Wal-Mart carries it for $3.89 a quart and right and a little over $15 for a gallon. Nice price for sy. Just started using it in my wife's durango.

 

[Gary Allan]

Since you're limited in cooling capacity I'd get a higher volume oil pump and larger cooler for the oil (as Curious suggested). Being a carb setup, I'd probably use a straight 40 weight dino since you'll probably be changing it often. Syths would be nice, but your fuel managment will make them a waste, IMHO. The 15w-40's would be the easiest to find.

There was one mention of the internal bypass possibly making your cooler null and void ..or at least less then fully effective. You may try and temporarily defeat this to see if things are better. It's not hard to do ..or to reverse. I'm unsure of the filter # ..but I believe that there is a 13/16 thread filter that has it's own bypass valve. I'm unsure of the gasket size. If that's an alternative (the filter) then just leave the internal bypass plugged.

Other that that, louver the hood in the low pressure area behind the leading edge. I don't know how this works in your styling scheme or budget to do it right.

You may consider tapping an oil temp gauge somewhere in your system.

 

[Mach5]

At least as a temporary measure, I'd use a synthetic oil. It's cheap compared to going through the engine again.

I'll second the oil temp gauge idea. Without data you're just guessing as to the root cause of the problem.

Ceramic-coated headers will help. By the way, I killed the starter on my '89 GTA with heat from the headers. I went to a Summit mini starter which seems to have fixed my starter issues.

 

[Black Bart]

posted December 10, 2005 09:03 PM
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Good question, JTK. I have been battling with that idea for months, and, if I can't find an oil that can deal with the temperature, that will be my next step.

The reason I haven't wrapped my headers yet is twofold. One, wrap kills headers quick. Wrapped headers will last two years at best, and with the humid climate here, I'm afraid they'd be rusted through in a matter of months. I probably should have bought ceramic coated headers in the first place, but we live and learn

I have been running wrapped headers for 6 years and they are still in excellent shape but they are ceramic coated. I think that you have more of a heat issue than oil. When you solve the heat the oil problem will go away.