Depends on driving conditions. If tracking the car or running it hard in high temp environments, 20/50 makes sense. The Diablo is rated at 10/40 as this would cover common drive environments for a car like this.That said, the design intent was to not push the engine until it reached operating temperature and the oil pressure decreases.
As you can see in these videos, the science and engineering now point to 0/40 so that start up pressures are reduced and will help extend engine life. Worth watching so you can make an educated decision.
I would never track a Diablo, but I put that out there because that is the only justification to use such a high viscosity oil. Also if your doing long sporty drives in high temp parts of the country. I used to run Valvoline VR1 Racing oil but had switched to 0/40. I find for my Diablos, the oil pressure stabilizes a lot quicker after start up.
So to help provide some insight on cam wear, in the 1990's through early 2000's oil type was a concern in Corvette circles as synthetics became more popular. For early C2 and C3 Corvettes, cam wear was reduced with high zinc oils. The 1990s C4 engine design reduced engine wear design issues and synthetics became the oil of choice due to their long term stability. The concern back in the 90s was that the synthetic oils at that time were not as effective as zinc for coating the cam surface creating more heat from added friction which translated to cam wear.This logic would definitely apply as well for the Countach.
Synthetics have improved dramatically over the last 20-30 years and it would be interesting to hear from a real engine oil expert as applied directly to the Diablo engine design. I suspect what they would say is both high zinc and synthetic are acceptable but if using a non synthetic oil, change oil frequently.
My 91 Diablo has 53000 km and has not had any issues. I have owned it since 2005 and taken really good care of it doing most of my own maintenance and the car has been bullet proof due to proper maintenance. My head explodes when I read about owners who let the car sit idle for years and expect it to be as reliable as a regularly driven fully maintained Diablo.
I purchased this car almost 2 years ago and trying to get it perfect. It had an oil leak between the engine and transmission. I wasn't comfortable taking the engine out so drove it to Vinnie's Exotics in Baton Rouge. I think he does good work, and I know his family well. He removed the engine and found that the transmission seal was the problem. There was some seepage on the valve covers so he was going to replace the seal there. That's when he discovered wear on one of the cams. New one was $18000, so we sent it to a place in California to be reworked. Low and behold they had done that cam for the prior owner years ago. Will soon be putting the car back together hence my oil question. Leaning toward 0W-40 synthetic.
I understand the debate on oil type but to be honest, your issue would seem to me to point more towards an issue in the motor than with the oil. Is one of the oil passages plugged, did a cal cap come loose, etc? You may consider drilling out the oil restrictors to the heads as well because I have heard from a reliable source that the Diablo lacks oil to the heads.
Before putting the cam back in be sure the sprocket is removed and the inside of the cam is cleaned thoroughly as well as ALL of the holes to the lobes. Do not assume the machine shop has done this.
Agree with Seth. I don’t think yours is an oil type issue as much as it is a supply issue to your cam.
my mechanic Josh @veloce motors prefers 20 W 50 as Geno said so does Steve at Driven Exotics. The 20 figure is the important one on cold start up and it’s just way too high for me particularly in the Pacific Northwest were the ambient temperatures are chillier than the rest of the US, generally. I prefer 5W 40 because of the cold start up and have found that the temperature of the engine gets to operating quicker and oil pressure falls quicker during start up sequence (~3-5 minutes) which means that the oil is lubricating better at the critical moments when it’s cold. That said, higher heat does not get carried away with a 5 weight as much as it does with a 20 weight so as a reminder if you plan on long hard drives with high RPMs and high temperatures switch to a 20 W 50. The good news with these cars is they are so easy to change the oil.
for what it is worth my mechanic also says to use synthetic because the technology has gotten so much better in the last several decades. really not sure about the zinc content and it’s lasting affects.
The bad one is the left hand intake camshaft Part # 001229370. All the others were fine and in spec when tested. That one camshaft is the very most expensive from Lamborghini, so I suspect it is the one that get damaged the most.
As far as oil, I am in Louisiana and the car is stored in my climate controlled shop. So it is never exposed to cold temperatures. More on the hot side here.
From what I can see, that so shows some sort of wear and tear on the right side of the photo versus the left which tells me it’s not the oil but some particulate or that particular valve is out of adjustment.
I agree with Mark. Being that it looks like this is only one lobe it doesn’t seem like it would be an oil problem unless there is a blockage to that lobe. Where does this lobe fall on the camshaft? First, last, middle? It could just be the picture but it looks like the shim on that valve sits much higher than the one next to it. It also looks like there is wear on the backside of the lobe which shouldn’t even be touching the shim/bucket if the lash is set properly. Definitely look at the entire setup of that valve. Pull the bucket out and make sure it moves freely in the head, check your springs, guides, buckets and valves. It probably would not be easy if you only have the valve covers off but I would check for a bent valve. It could be that the last time the previous owner fixed this issue they never found the route of the cause and just slapped it back together and crossed their fingers. If you do this I would expect it to happen again. I would also be very concerned where all of those metal bits ended up and what path they took to get there. There is quite a fit of metal worn off that lobe. There could be some collateral damage from that deeper in the engine. Hopefully it all got caught by your filter before going elsewhere. You may want to cut open your filter to see what it caught. Good luck with this and keep us posted with what you find.
Semi-synthetic LIQUI MOLY specialty oil with an additive package containing Molybdenum Disulfide (MoS2). The unique formulation adds a high pressure and temperature resistant lubricating layer to all friction surfaces for added wear protection and safety reserves. Reduced friction will...
You can find it on Amazon, works very well
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