LethalTT

My builder told me he wants me to run Rotella 15W40 diesel oil and zinc additive. 408 iron block with F1C. He said that running E85 is even better to run the rotella. He tells me this what they run on their race cars.

old motorhead

I'd run what he recommends. Engine builders set up clearances for specific weight oils. If you're OK with the builder, don't question his lubricant rec. Just do it

I run 15/40 diesel oil in all of my engines except one. My new GS Vette. Although making way more HP than a stocker, I'm still using what the General recommended.. 5/30. The clearances in the motor didn't change because I added a supercharger.

I'm sure someone will jump in a say their tuner recommends 20/50. Their tuner didn't build your motor though.

LethalTT

Thanks. I just got nervous cause I starting reading and saw on here where someone said that gas motors dont like diesel oil and it could foam at high RPM. Anyone else have inputs?

Blackonblacksls

With that being said. Aren't the factory tolerances very vague?

As in a lot of way to the larger side and smaller side?

lane_change

I used to run diesel oil in my last Z06 with no issues. Losing zinc from all modern oils is a pretty crappy deal, so either go diesel or go expensive.

old motorhead

I don't know about vague, but there is a range that the bearing clearances need to be in. Something like either side of .002. Maybe .0015 to .0025. Race engines designed for a heavier oil would have wider clearances.

ajrothm

I run Delo 15w40 diesel oil (non synth) in my 496. That's what the engine builder recommended so that's what I run.. I have 14k miles, 80 1/4 mile passes and countless passes on the street....still has great oil pressure, oil always looks great at 3k changes and it doesn't leak a drop..

Stick with what works...

CI GS

Read this:

http://540ratblog.wordpress.com

It gives you a lot to think about, especially the apparent debunking of the Zinc additive "myth".
The other thing to consider is that diesel motor oil is formulated and spec'd for slow-running Diesel engines that tend to have more bearing clearance than the typical gasoline engine. It also has an additive package for soot-dispersal, etc. that simply isn't needed for a gasoline engine.
BTW: Most race-engine builders these days are running lower viscosity oil and setting up clearances accordingly. Their reason: they make more HP that way, and thinner oil drains back to the sump quicker, which is very important when you're turning RPMs 3-4 times higher than a typical Diesel engine can attain.
Another thing to consider is that one company's 15W-40 might not actually be the same viscosity at the same temps as another companies. You need to look at the actual spec sheet for that oil (and you probably need a degree in chemistry to figure it out anyhow) to see what the actual viscosity is.
I would ask the builder to explain why he is insisting on using this particular oil and ask about how he clearanced the engine (get him to give you the actual clearances) to get an idea if he actually has set it up for that viscosity oil. The old "this us what we run in all of our engines" simply isn't good enough. Basically, any engine oil will "work" for a while and you will generally only know if it isn't working after the bearings wear out to the point that you see oil pressure loss (or suffer catastrophic engine failure!) which could take a while.
I run URSA 15W-40 oil in my Hitachi /John Deere excavators and I believe in it, but I realise that their engines get warned up in the morning and run consistently at ~1800-1900 under load all day with a fairly consistent engine temp and load. That's a much different scenario that a street car that gets started and driven off in the morning, seeing many gear changes and start and stop, RPM cycles, several times during the day, and so is run at varying loads, rpm and temps in any given day.
The ideal thing seems to be to have an oil that's thin at startup to get oil to the bearings quickly, yet thickens at warmup to a viscosity that is sufficiently thick that it gives you the best shear/load protection without causing pumping losses from being too thick.
I'll leave the chemistry to the folks that make these oils because they know a hell of a lot more than what I do and that's what they do for a living.
My suggestion: Find a good, widely recognised synthetic oil that's spec'd for your type of engine (taking clearances into account) and your operating conditions and go with that. If it turns out that you actually need a 40weight oil, I would suggest that you run something like Mobil 1 0W-40 or a 40wt multi-viscosity synthetic from Redline, Amsoil, Valvoline, etc.
Just my 2 cents...

jon6.0

I run Amsoil Z-Rod oil because it does have a lot of extra zinc in it. Run the weight your builder recommends and builds the motor for.

lt1z

I run Driven conventional 10w40 in my new motor. No issues here. I will still keep a 40w in it after switching to synthetic down the road.

b16gsr

I have always used Mobil Delvac in my diesel trucks, LS motors(several of them) and my Big Block.

Unreal

Zrod 10-30 but my builder said use 5-30. I use the 10-30 just because it is so hot here the difference between 5 and 10 isn't a big issue since it is only driven when it is hellish hot outside.

high9s

I needed high zinc oil in my supercharged big block Chevy per engine builder. He wanted Valvoline 20-50 Dino (non synthetic)

If high Zinc is a priority for you engine check out some of Valvoline's lower viscosity oils, they have synthetic and dino good stuff.

http://www.valvoline.com/products/br...ng-motor-oil/6

Streetk14

I'm not going to pretend I'm a chemical engineer, but I'm pretty sure the only difference between 5w30 and 10w30 is how thick they are when cool. Even an oil with a "5" cold thickness is usually way thicker than needed in a modern engine. Something like a 0w30 is really ideal to prevent wear on cold startup.

I've spent more time reading about oil on www.bobistheoilguy.com than I'd like to admit. The way oils are rated isn't exactly clear to most car guys.

Streetk14

Lots of good reading here if someone has some time to kill: http://www.bobistheoilguy.com/motor-oil-101/

Unreal

Yah, you are correct, but since it never gets cold here, and I like the amsoil, I run the 10-30. If they made zrod 0-30 I would run that.

Streetk14

Gotcha. I like Amsoil products, but finding them local is a pain. Been sticking with Mobile 1 for that reason. They make a European formula that has ZDDP I think. Need to look into that some more.

OP,

Ideally, an engine with stock GM bearing clearance wants something with an operating viscosity of "10" at all times. A synthetic 10w30 oil has a thickness of around "75" at 75 degrees, while it's a "10" once warmed up to 212 degrees. A 0w30 is going to be that same "10" at 212 degrees, but will only thicken to a "40" at 75 degrees. Closer to "10" you can get with cool oil the better. The less an oil thickens as it cools, the better.

If your engine builder built the engine with wider clearances, then you'll probably want a thicker oil when at operating temp. A 40 weight oil has a thickness of around "14-15" at 212 degrees. That's fine if the engine was built this way. But I wouldn't run any 15w40 oil -- there's just no reason. Even if you live in a warm climate, it's way too thick on cold startup. Something like a 0w40 or 5w40 would be much better at reducing cold-start engine wear and will be much closer to the thickness the engine wants as it warms up.

Looking at Amsoil's oil specs (just as an example), their 15w40 diesel oil has a rating of "103" at 104 degrees. Their European car 5w40 has a rating of "83" at 104 degrees. Still much too thick, but closer to the 14-15 your engine tolerances call for. These numbers will get wider apart the cooler the oil gets.

I think you can see where I'm going with this. Find out what's been done for internal clearances, and go from there. If they really want you to run that Shell Rotella, I believe they make a 5w40 version.

speedz06

I worked for an engine oil manufacturer for over 15 years and have always been a tech head.
Before that I went to 2 year Diesel/Auto college and worked as heavy equipment mechanic. Worked for Mitchell racing on Long Island too. Built several motorcycle engines, read hundreds of tech bulletins and studies while going up against competitors to win the business of the largest truck, taxi, ambulance, railroad, bus fleets in the country.
I had to know oil.

The 15/40 motor oils, particularly the higher spec premium brands are far and above the conventional automotive oils in many ways.

Just check with him (engine builder) to see if there is a synthetic 15/40 available as that is truly a better product.
The new hydrocracked base stock 15/40's can perform almost the same as a full synthetic though. Conventional oils have gotten to be very good due to advanced refining techniques, but there are still some cheap oils out there.

Be aware that most companies offer 2-3 different price and performance levels of 15/40 and you should be sure to get the best.
For example, see Mobil Delvac series offered in economy and premium versions.

*The question is, does your builder want the actual weight or just the specification and additive package these oils offer?
15/40 motor oils are generally in a different specification class (higher) for heavy duty use compared to other oils. They meet automotive and then continue on to meet heavy duty use specs that most automotive spec only oils cant handle.


If it is just the spec, the synthetic Delvac 5/40 or a competitors brand should be better.

Just as the vettes come with Mobil 1...IMO the Delvac 1 also made by Mobil is a higher grade product.

Engine oil specifications are readily available in a spec sheet same as an engine or motor.
We quickly scan for horsepower, torque, what type of valvetrain, forged internals, lightweight metals, max rpm, type of fuel system etc...

Well it always made me wonder why technical minded people rarely took the time to learn about the specs on a motor oil.

TBN, pour point, Sulphated ash content, zinc content, oxidation resistance etc.
These specs tell how an oil performs just as engine specs give us some idea how a car will perform.

There is plenty of great easy to read literature out there. Just be mindful of advertisements vs. real unbiased information.
ASTM, society of automotive engineers and other have tested oils in fleets of a hundred cars,or trucks, disassembled engines and actually weighed each bearing, piston ring etc to see how much actual wear different oil specifications protect against.
A "pre measured engine test" or something like that.

You can take just about any 15/40 motor oil and know that it is chock full of higher detergency,(magnesium, calcium) dispersency and other factors such as antiwear agents than a typical automotive-only motor oil. They are also known to have excellent low temperature capabilities in order to reach turbochargers via that small diameter tube. This is measured in "pumpability" or "pour point" Synthetics kick *** in low temps.
A 90wt synthetic can out perform a 20wt petroleum based oil in low temperatures.

It's hard for me to start discussing motor oils without running on.

Hope this helps.