Oil Temperature

I have a rebuilt 350 Mercruiser. The oil and transmission coolers replaced. The engine runs in the cool range. I feel the oil lines to the oil filter and they feel pretty hot to touch. I hit the oil filter with my heat gun and the filter reads 165 degs. Is this too hot ? or as it should be ? Thanks for any educated opinions.

I think lube oil should be about 160 to 180 degrees.

You say "the engine runs in the cool range" .. Does that mean cool ... coolant? Probably. The oil temp is more or less independant of the coolant. The coolant is artificially controled (temp wise) by the thermostat. Change thermostat .. Change coolant temp. But lube oil temp is comparatively telling you the actual temp of the engine as there is nothing but a small oil cooler that uses coolant to stabilize the oil temp. So I'm guessing you're oil temp is actually about 165 degrees. I would'nt want mine much cooler and would'nt mind if it were a bit higher. Sounds good to me. But I'm no engineer.

Many boats has it right. Oil temp is much more a product of the load on the engine. The oil cooler actually takes a fair bit of the total engine heat out of the engine. 165 is definitely on the cool side for oil, but it also depends on what the engine was doing. For a gas engine, 180-200 is a normal range. For diesels, just a bit, maybe 10 degrees higher.

Ken

Best for oil to be around 210F at higher loads. This keeps moisture from building up in the oil. Many engines keep oil too cool, on those it should be changed more often.

For those that underload running a hot thermostat may be beneficial.
Any thoughts?

Thanks to all for the info. Good cruising!

Yep, good to have hot tstats for light loaded engines. In the OP's case, engine might be sea water cooled, and then you do want to keep the lower temps to prevent mineral precipitates from forming. If FWC, then get 180, 190F tstats.

My Cummins came with 160F tstats, I swapped them out with 180's as I never run engine up near full power except to check rpms and boost.

Lehmans and Yanmars use sea water oil coolers, which baffles me. Oil is cold unless at full power.

There are adapters for oil filter mounts with a thermostat and taps for oil coolers. I've used them and oil temp control was much better, even using sea water oil coolers.

Ski in NC said:

Lehmans and Yanmars use sea water oil coolers, which baffles me. Oil is cold unless at full power.

There are adapters for oil filter mounts with a thermostat and taps for oil coolers. I've used them and oil temp control was much better, even using sea water oil coolers.

Click to expand...

That is funny, ski. My last boat with a Yanmar I had to take it out and put it under load to get the oil up to temp before I could change it. The problem was that I had to idle into the marina for about 5 mins. By the time I got to the slip, the oil was cold again. I am talking put the dipstick on my forearm with no pain cold. I even considered changing the oil in the middle of the bay. Obviously not a smart thing to do with a single engine boat. But it always frustrated me that I could never really get the oil hot enough to do a proper oil change.

My wife's Audi has a oil temp gauge, if I remember correctly it runs around 230f.


Sent from my iPad using Trawler Forum

manyboats called it, hotter than 160 is better. You need the oil to get hot enough to evaporate any water or diesel fuel that got into it.

When I was involved with manufacturing camshafts and laboratory dyno testing we artificially heated the oil to 240 F which supposedly was the max it should see in a properly operating gas engine (Ford 4.6L/5.4L).