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Highest OIl Temps that are safe

Old 05-25-2017, 08:40 PM
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Default Highest OIl Temps that are safe

The question is what is the highest oil temps that oil can take before issues start?

To start with had a 18 inch long 2 inch diameter cooler and had no idea what the oil temp was. After a short time I wondered why the oil was so black and was running 20W50 Caster oil. Also had 3/8 ID oil lines and standard Merc oil filter block adapter.

This year, installed 10-AN oil lines and oil adapter, along with 525 oil cooler, using Brad Penn straight 50W. Pressure after getting to or above 220 degrees I'm seeing 70 to 80 psi oil pressure. My 530 HP motor is at 220 degrees running 3400 rpm's and gets to 240 degrees at 3600 rpm. When I go higher and at WOT it just keeps climbing. Did not do a lot of running so this was just initial readings with a 18 mile round trip. This was 9 miles up, stop swim and later come back. Water temp is around 85 degrees so its still a bit cool.

Plan to install AFR meters to check ratio, and also water pressure gauge in the block to make sure water is flowing. Also plan to go back to 20W50 Castor oil. Have brand new impeller and Hardin Marine SS water pump housing for this season
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Old 05-25-2017, 09:26 PM
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Why are you running straight 50w? Engine specs? Bearing clearances?
You might just be creating a s#itload of shear heat in the oil.
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Old 05-25-2017, 10:35 PM
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straight 50 for a 530 horse engine,please tell me why you feel the need for 50 wt oil.
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Old 05-26-2017, 04:59 AM
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Where are you reading temps?
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Old 05-26-2017, 05:34 AM
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I would can the 525 cooler and go with a larger aftermarket
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Old 05-26-2017, 05:56 AM
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How big is the 525 oil cooler ?

BTW: Carb tune (A/F ratio's) can have a huge impact on oil temps. So, I would wait until you get that dialed in before spending more on parts.
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Old 05-26-2017, 06:27 AM
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After build was running 20W50 but was only reading 25 psi and would dip slightly lower when coming off plane. Working with another it was decided this season to try 50W to get the pressure up. Installed a mechanical gauge Tee with the electrical gauge. Found a 15 higher reading with mechanical gauge, so figured a 100 psi sender was installed instead of an 80 psi one. Installed a 80 psi gauge and now the gauge reads within 2 psi of the mechanical.

With the gauge offset issue discovered and pressures running so high I'm changing back to 20W50 before I take it back out. Going to reinstall O2 sensors and measure AFR to determine if this is also an issue.

Reading temps at the filter head before the cooler

The old cooler was 2x15 and the new is 2x21 and looks like this one

[ATTACH=CONFIG]567703[/ATTACH]
Attached Thumbnails Highest OIl Temps that are safe-cooler.jpg  
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Old 05-26-2017, 07:04 AM
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Technically, a straight 50, and 20w50, will have the same viscosity at 212*. I've ran both , and never noticed higher oil temperatures with straight 50. I doubt thats the issue.

I definitely would make sure it isnt running lean.

Also, what are you running for water thermostat, if any, and how hot are the water temps? Are you running a crossover? What size hoses are feeding the exhaust manifolds? The biggest oil cooler in the world, wont cool well if it doesnt pass much water thru it. Whether thats from impeller issues, or, restrictions after the cooler, like running small lines to feed the exhaust manifolds.
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Old 05-26-2017, 07:17 AM
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Going to 20W50 right now so the cold start up will be easier. If things start falling in line and get things where it needs to be, might go to Brad Penn 40W.

The motor is running the standard cooling hoses and does not use a crossover. Have a 140 degree TS and motor runs at 160 to 170 at cruise speed. At WOT for some time it doesn't go above 175. Have a water pressure gauge coming in to attach at the block drain plug.

There is no TS in the oil cooler lines

The motor (MPI) was tuned using AFR originally, but going to check to see if things have changed. If 250 or 260 degrees are fine then I'll pay more attention to other things I'm working on, but other threads lead me to think something may be wrong.
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Old 05-26-2017, 07:27 AM
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Wonder why its running 160-170 water temp, with a 140 thermostat. It should be running, well, around 140.

Its sounding like your high oil temps, may be due to water flow issues .

I personally, would not run my oil at 260 degrees. When everything is right, your oil temperature, and water temperature, should stabilize, no matter how hard youre running. Ive ran in some runs where for 30 plus miles at 5k rpm or higher, my oil never went over 200-210. I only have 8 plate coolers with 800hp engines. Most suggest a 13 plate cooler for that, but i believe what helps me, is i dont run water stats, so the block is doing some oil cooling, and i have lots of water flow, with good water psi at high rpm. Now, that 8 plate, might not get it done, if i restrict water flow, or stick a 140 stat in the engine.
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