What oil should I use?

[Terrh]

I've been reading around these forums for a while and I think I have more questions than answers. Before I came here I thought I knew it all about oil! Now I feel like I know nothing.

Anyways, Thought I'd ask what I should use in my weekend/fun car.

The car is a 1992 Nissan Skyline GT-R. 2.6L twin turbo 6cyl. I've more than doubled the horsepower over stock and the car sees HARD use, but is still a street car. I don't mind changing the oil every 5000KM but it has a large capacity and synthetics are expensive so I don't want to have to worry about changing it more than that.

Owners manual says to run 7.5W30, which I've never even heard of. Before (on my first motor) I ran 10w30 Royal Purple which seemed to work well, but I did notice the head made more noise than I'd like. Now the car has large cams and heavy valve springs/oversize valves. Redline is in the ballpark of 9000+ RPM.

Car tends to be driven on short/medium length trips, rarely more than 100 miles at a time, though that will happen a few times a year.

I religiously warm it up for 2-3 minutes before driving it, even in the summer, as it has aftermarket forged pistons and a large-ish piston to wall clearance when cold. (3 thou on a 3 1/4" bore) I don't bother waiting for the oil to warm up, as that takes a solid 10+ minutes of driving it seems, even in the summer.

The engine has zero problems and as of this post is brand new - hasn't even ran yet.

Important stuff about the engine: Driven hard, turbocharged, solid lifters/non-roller cams, DOHC, etc. Oh, the car has a large oil cooler and will never see high oil temps. The turbos are water cooled. I've got a remote-mount oil filter and currently have a Wix 51515 (PH8A) filter in it, which is at least twice as big as the stock filter.

If anyone wants more info feel free to ask! Thanks in advance for any insight.

 

[addyguy]

I'd be inclined to use a 5W-40 HDEO like Rotella 5W-40.

You can get it at both Canadian Tire and WM in Canada, and it isn't too expensive for 5k changes.

Should fit the bill well.

 

[ARCOgraphite]

The OM is out the window since the engine is built/modded. What does the builder recommend? What is your sump size/temp? Are the TC h20 jacketed? Unless you are willing go into boutique oils at 10+ a Litre, 4T synthetic supebike oils would work fine, as well as high spec 5w-40 Shell (Helix) Ultra, and of course M1 0w-40 or just about any 10w-40 syn. I dont see you saving much $$ over the RP unless you are willing to try M1 TDT or Rotella T6 which prob would do fine.

 

[ARCOgraphite]

Originally Posted By: Terrh
...
The engine has zero problems and as of this post is brand new - hasn't even ran yet. ...

Just saw this

 

[FL_Rob]

Is there any way to speak with both an Amsiol and Redline engineer,(at least for the break-in oil)if you give them detailed specs? Aside from that,maybe the cam manufacturer has recommended oil specs.

 

[dtt004]

Hi.

How do you run the engine and its hard use when you haven't run the engine yet? I am confused.

If it was rebuilt because of previous failure, so you know the environment that it will be operating in, then I can kind of see where you are coming from.

The short answer is that...whenever you increase power, you always decrease reliability. That's just how the world works. No oil can withstand everything that's thrown at it, including the driver's own foot. It's a fluid. That's all it is. It's operating in areas at extreme heat and pressure.

You won't be able to find an oil that will make the car last.

You can prolong it's life in a miniscule amount by changing the oil often. But as long as you continue to drive it like you described it, your engine has no chance.

As an engineer, I design and develop engines for motorsports use. I don't know everything about everything, but I do know enough to give you my opinion. If you doubled the stock horsepower, that is extreme modification. People go out and buy 1000-2000 dollar exhaust systems to add 6-10 horsepowers. Honestly, it really is. Forced induction stresses out the engine even more so than a naturally aspirated engine.

Expensive oils will not help at all. You are not driving it often anyways. Expensive oils are usually made from non-petroleum base stocks, or blended with them. This allows them to operate better at higher temperatures, and for prolonged periods, as well as offering longer oil change intervals.

An engine oil cooler COOLS DOWN the oil through a temperature gradient. It's misleading to believe that the oil will NEVER see high oil temperatures. I guarantee that engine oil will be so hot it won't matter if there is an oil cooler or not. It's very very difficult to remove heat from oil because it absorbs so much of it, and retains it as well. That's a chemistry lesson for a later time, but you can kind of see the picture. What takes longer to cool...water or oil? In the same type of container, environment, etc. An oil cooler is meant to prevent COKING of the oil. It was never meant to make the oil cool.

Aftermarket forged pistons will be tough to deal with at this level of power. I am assuming these are ordinary forged aluminum alloy pistons yes? It's probably a eutectic alloy with silicon. TO better withstand the warping and increased cylinder abrasion, I would recommend changing these pistons out and installing hypereutectic pistons, wherein the aluminum alloy matrix is supersaturated with silicon. Aluminum has a very high coefficient of thermal expansion. Silicon does not. When Silicon becomes the saturate, it will minimize the chance of extreme cylinder warping, increasing engine reliability through better sealing and less wear. It also has the advantage of being extremely hard. However, I actually take that back. You will probably need to have the engine block cast from the same alloy because the silicon is so hard that unlined iron cylinders would be destroyed.

So another point that you have to accept. I believe the engine is an iron block, with aluminum pistons. You will see lower life because the aluminum pistons will wear out and will not seal correctly. Or the iron cylinders will be eroded to the point that correct compression cannot be achieved.

It's just the nature of the beast. You want power, you have to give up reliability.

 

[aquariuscsm]

You said you`d tried RP,their 10W40 has the most anti-wear out of all their street oils (as told to me via RP tech). M1 10W40 HM has 1000ppm of zddp,which would be another good choice for your Nissan.

 

[CATERHAM]

Since you have a modified engine I might increase the minimum oil pressure spec' the mfter recommended by 5 to 10 percent.
You likely will still be able to run a 30wt oil as long as your oil temp's don't get too high. I'd also run a HDEO.
I'd suggest Petro-Canada Duron 0W-30 with it's HTHS vis of 3.3cP.
A slightly heavier option would be Shell Rotella T5 0W-30 with it's HTHS vis of 3.4cP. I very much doubt you will need an oil heavier than this.

Enjoy!

 

[chubbs1]

If your engine is brand new I would be inclined to run a break-in oil like Brad Penn (straight) 30 for the first OCI especially since it is the summer and you are doing a short OCI. You can then switch to brad Penn 10w30. It can be purchased on Amazon. Most people I know who run highly modified engines use Brad Penn oils with excellent results but that would be too thick in winter.

I would also consider using HDEO's like the ones mentioned above. DELO, M1 TDT or use go back to RP which is a solid SL rated oil.

I would want to use something with a high ZDP content and is why I recommend using the Brad Penn 30w first. I hope this at least is a little help. Great Ride!!

 

[SLCraig]

Pics of the beast?
Love me my Nissans.

 

[chubbs1]

Originally Posted By: chubbs1
If your engine is brand new I would be inclined to run a break-in oil like Brad Penn (straight) 30 for the first OCI especially since it is the summer and you are doing a short OCI. You can then switch to brad Penn 10w30. It can be purchased on Amazon. Most people I know who run highly modified engines use Brad Penn oils with excellent results.

I would also consider using HDEO's like the ones mentioned above. DELO, M1 TDT or use go back to RP which is a solid SL rated oil.

I would want to use something with a high ZDP content and is why I recommend using the Brad Penn 30w first. I hope this at least is a little help. Great Ride!!


I had to change the "too thick for winter" part as I was referring to 15w40. I don't think you need 15w40...lol

High ZDP!! Go back to RP 10w40 if you can afford it, try Brad Penn or go with a HDEO to save $$ while still having a quality oil.

 

[JimPghPA]

When dtt004 said "
The short answer is that...whenever you increase power, you always decrease reliability. That's just how the world works."

He is right on target.

My personal pet peve is people who increase power but fail to increase the air flow, radiator size, and coolant flow for the radiator.

As you increase the power the amount of cooling required increases by the same porportion.

If you do not increase the cooling the engine is going to run hotter. And hotter parts and oil under higher loads (making more power) are not what you want.

 

[Terrh]

Wow, so many replies! Thanks guys! Hope this answers some of the questions:

The turbos have water jackets, and if I've been driving the car hard I'll let everything cool off before I shut it down.

It doesn't get used in the winter, ever.

This is the 2nd time I've rebuilt the engine. When I bought the car the original engine spun a bearing before I even got it home. ([censored], expensive lesson). I rebuilt it the first time with forged internals (forged steel rods, wiseco pistons) but left the head pretty much alone. It lasted 45,000KM of me beating it daily with around 400 horsepower, plus several cross-country road trips, etc.

I built the engine myself both times, only contracting out machine work that requires expensive/special tools (bores, crank grinding, etc), so I don't have a builder to ask what oil to recommend.

The first engine I built failed due to a valve guide cracking at high RPM and dropping into the cylinder, which produced a sound like rod knock. When I pulled it apart the cylinders had been scored from it bouncing around in there but everything else still looked pretty good. 5000KM Royal Purple oil changes kept everything looking brand new inside. I did have some odd bearing wear (visually) but couldn't measure anything on them they were worn so little. Everything checked out within spec still, and nothing was bent/etc.

This motor hasn't ran yet but I plan on treating it pretty much the same way. I built it to have fun, and I know that comes with the price of a short life. I just want it to last as long as possible with me having fun, I'm not expecting it to go 200,000 miles.

I will probably do the break-in process the same as I did last time. It might be a little overly anal but it worked. I changed the oil at 20KM (to get all the initial garbage and prelube out), 250KM, and at 1500Km I switched to mobil 1 10-30, and at 5000 KM I switched to RP 10-30. I gradually introduced it to more load and RPM over the first 1000 KM, and it saw full throttle/redline around 1000KM somewhere.

I've got an oil temperature gauge and I have to say the oil cooler helps control oil temps a TON. My temp gauge (which is pre-cooler, at the filter outlet on the block) rarely goes about 90-95C, and only once was I able to push the car hard enough for long enough to get the oil temps to about 110C. (at that point I had to let up on the car some, as the brakes had had enough too). Engine rarely sees coolant temps above 90C.

I don't mind paying the money for the RP, I just meant that at $80 an oil change (car holds 8 liters) it adds up fast if I'm changing it more than every 5000km.

Here's my favourite picture of the car, yes it's flying.

It's much better looking now, but after painting it I doubt it'll go airborne again.

 

[CATERHAM]

You gotta get some decent shocks for that car!!

 

[ChattZX]

Originally Posted By: addyguy
I'd be inclined to use a 5W-40 HDEO like Rotella 5W-40.

You can get it at both Canadian Tire and WM in Canada, and it isn't too expensive for 5k changes.

Should fit the bill well.


+1 on the Rotella T6, my Nissan 300ZX loves it and I do just about the same driving as you do.

 

[JimPghPA]

Read "Motor Oil by A.E. Haas".

There is something about oil also providing cooling, and the maximum cooling provided by it, being provided with maximum flow.

At maximum running temperature under maximum load, at maximum RPMs the oil will thin some. This is when you want the oil to be just thick enough to provide the desired oil pressure, and not any thicker. If the oil is thicker than required, there will be less flow, because of opening of the oil pressure relief valve, and or because thick oil will not flow as well. If the oil is too thin it may allow metal to metal contact.

The bottom line is, pay attention to what the oil pressure is at the maximum temperature maximum load maximum RPM, and chose a thicker, or thinner oil if required.

A good example of this is the use of thin oil for high revving race car engines.