Which 15W40 for built LSX?
Thread Starter
Launching!
Joined: Feb 2012
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From: IL, USA
Which 15W40 for built LSX? So my engine builder suggested I use 15W40 for my supercharged lsx 388 but said he prefer a non diesel type 15w40. Anyone know of any non diesel oil of this weight? All I found was Redline. Idk if I could use 15w50 which Amsoil makes... Would be nice if I could get away with 10w30 avail everywhere lol
Thread Starter
Launching!
Joined: Feb 2012
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From: IL, USA
Yeah I almost bought some Rotella 15w40 but then he said make sure its not diesel oil so I'm confused as ALOT of guys on here use the regular diesel type 15w40.... what will happen if I get the diesel 15w40???
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I am not sure about LS but I have run 15-40 rotella diesel engine oil in my flat-tappet cam truck engine for its life and its been perfectly fine. When new its bearing clearances were 1.5 thousandths on the mains and rods or so. Seems to be a perfectly okay street engine oil. It may not be scientific but I've seen rotella 15-40 run in blown big blocks, hemis, and lots of boats in addition to little four-bangers and modern engines.
Diesel oil is a bit like old-school flat tappet cam engine oil, it contains more high-pressure friction compounds, like Zinc Phosphates which is what "ZDDP" is on the label. This same material is the "AW" or anti-wear compound that gets added to "AW" hydraulic fluid.
Diesel oil is a bit like old-school flat tappet cam engine oil, it contains more high-pressure friction compounds, like Zinc Phosphates which is what "ZDDP" is on the label. This same material is the "AW" or anti-wear compound that gets added to "AW" hydraulic fluid.
Thread Starter
Launching!
Joined: Feb 2012
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From: IL, USA
Yup Well I finally got ahold of my engine builder and he said I will be fine with 10w30 according to the clearances on paper from my build. Now that makes things a lot easier! Guess I will find a quality 10w30 racing oil. I've had good luck with Amsoil in the past so I might try their 10w30 racing oil 
Last edited by momofx; Nov 24, 2021 at 09:08 PM.
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I read that diesel oil is not designed for higher RPM operation. Apparently its more prone to aeration/foaming. I'm not an expert on the subject. Just stating what I've read.
I have a buddy that switched to Rotella on his LS7 that was spinning 7600rpms and ended up losing a few bearings. Coincidence? Who knows.
I've used Mobil 1 15-50 with zero issues. Valvoline VR1 is a fantastic oil and they offer it in 10-30.
I have a buddy that switched to Rotella on his LS7 that was spinning 7600rpms and ended up losing a few bearings. Coincidence? Who knows.
I've used Mobil 1 15-50 with zero issues. Valvoline VR1 is a fantastic oil and they offer it in 10-30.
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Verdad Gallardo Well I finally got ahold of my engine builder and he said I will be fine with 10w30 according to the clearances on paper from my build. Now that makes things a lot easier! Guess I will find a quality 10w30 racing oil. I've had good luck with Amsoil in the past so I might try their 10w30 racing oil
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Joined: Oct 2016
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From: PDX-OR-USA
I worked with some really smart guys who worked for a major oil company and provided track-side support to American Leman ,,,
Don't run race oil on the street it has almost NO detergents or rust inhibitors,
They do everything to it to prevent foaming and give up a lot of other stuff since it will be in the car less than a couple hours total for each use..
Makes sense if you consider they burn about 5 grand in fuel on a race weekend and the oil cost is 200 bucks.
Don't run race oil on the street it has almost NO detergents or rust inhibitors,
They do everything to it to prevent foaming and give up a lot of other stuff since it will be in the car less than a couple hours total for each use..
Makes sense if you consider they burn about 5 grand in fuel on a race weekend and the oil cost is 200 bucks.
Interesting oil story, I have a friend who's a national champion funny car driver. When the economy tanked in 08 he drove for another team. The owner of the car was a GM engineer, and he ran Valvoline VR1 and had a small camping stove and a large cooking pot. Between runs, they'd drain the oil and boil the alcohol out and dump it right back in the Hemi.
Launching!
Joined: Aug 2020
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From: Phoenix AZ
Duh… I read that diesel oil is not designed for higher RPM operation. Apparently its more prone to aeration/foaming. I'm not an expert on the subject. Just stating what I've read.
I have a buddy that switched to Rotella on his LS7 that was spinning 7600rpms and ended up losing a few bearings. Coincidence? Who knows.
I've used Mobil 1 15-50 with zero issues. Valvoline VR1 is a fantastic oil and they offer it in 10-30.
I have a buddy that switched to Rotella on his LS7 that was spinning 7600rpms and ended up losing a few bearings. Coincidence? Who knows.
I've used Mobil 1 15-50 with zero issues. Valvoline VR1 is a fantastic oil and they offer it in 10-30.
LS7 to 7600 rpm is stupid -
RPM Limits 4 inch Stroke Crank goes into some details.
~7,600 rpm is over 5,000 fps (feet per second) when 4 inch stock stroke LS7 crank is used. That's a high crank speed if there much duration at that high rpm etc. Some folks have spun 4 inch cranks to ~10,000 rpm etc.
I use Royal Purple 15w-40. I believe that is what the lifter company stated was the max weight oil you can run in the specific lifters I bought. Last oil change, I just threw in 10w30 though. Seemed like a lot of extra expense for nothing.
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As a heads up, we worked with “the” petroleum company that does all the formulations for the expensive international name brands. Summit performance oil is the same stuff in the bottle but at a significant savings. It is considered organic. It is zddp but we don’t have the specific 15/40 weight. If that’s something you guys have an interest in us adding, please let us know.
