Hot Oil

[Robert Bishop]

I was flying to the convention over the HOT California valley and my oil temp got up to 230 degree so I turned around went back home. I know there's been some talk about this in the pass. I was reading in one of the 170's books were some people are putting Slick 50 in there engine and it lower the temp by 20 to 30 degrees also were can a person get new baffling trim ? Ideas or suggestion welcomed.

[Bruce Fenstermacher]

To bad you had to turn around. If it hadn't gone much over 230 I'd have continued to the convention where we all could have looked over your installation and given you lots of ways to spend your money.

Do a search here on the subject and you will see a lot of information on this subject. I'll just note a few.

First your baffling should be in good shape. You can use the red silicone baffle to accomplish this. Almost any baffling sold will work. George (GAHORN) may be able to get some that is identical to the original if you want original.

Second everyones oil seems to run hot but is it really hot. It seems our 170 oil temperature indication installation isn't very good and in most cases not accurate as to what is really going on inside the engine. What I'm trying to say is if you could measure the oil temperature elsewhere it may not be as hot. Of course we are left with this installation and the printed limits Cessna/Continental came up with. You will note the cooling tubes at the back of your baffling which should be pointed at the area of the accessory case where the oil temperature probe. These tube may help cool the oil but they at least cool the oil in the area of the temp probe and therefore your indication. Make sure the tubes are directed correctly.

Third your temp probe and gage may simply be incorrect. This is common. You might want to calibrate it by placing the temp probe in some heated oil and marking the cage to the none temperature of the oil.

Fourth if you aren't already, simply running straight 50 weight oil raises the oil temperature limit to 250 according to Continental.

[Robert Bishop]

I do run Shell 50wt oil but I still don't like the temp to be that high, it don't seem right. I also have a JPI instrument scanner installed with a oil temp probe installed in the front of the engine,so I think the temp is reading right.I have gone as far as flying untill the tempture is at it's max landed removed some oil from the drain into a coffee cup and check the temp with a candy thermomter and found it to be only 160 dergee or so. I guess I,ll stop flying untill winter! Yea Right

[Dave Clark]

An Arizona mod that works very well but has no approval basis is to open the air intake below the prop to as large as the pan baffle allows. If I remember right it's about 1/2" more on three sides. You need to make a new back up piece and rivet it in but that's very easy.

It drops the oil temp a lot. Once the paint is touched up most people never notice it. A new winterization plate would need to be made if you think you'll need it.

[Bruce Fenstermacher]

If you are sure there is nothing wrong with the oil temperature measuring equipment and your baffling is in good condition and your sure there is nothing otherwise wrong with your engine, then I'd think about modifing the aircraft.

Let me relate what happened to me. My engine oil usually ran about 180-190 and I never understood why anyone would have oil temperature problems. While I was rebuilding my engine I realized the engine never had the upper cylinder baffles installed. The aircraft at one time was used for skydiving in Florida and as it turns out perhaps someone removed them to lower oil/engine temperature.

I manufactured new upper baffles and installed them on my rebuilt engine. Quess what. My engine oil now runs 225. Could be the engine is tighter and runs hotter but I doubt it.

Based on this experiance if I wanted to lower my engine oil temperature in an unapproved way but one that could easily be reversed, I'd make new cylinder baffles both upper and lower but trimmed down evenly so the exit below the cylinder was bigger. I'd continue to reduce the size till the oil temperature came down where I wanted it but not lower that 180. By reducing the cylinder baffle size you are letting more air pass over the cylinder AND over the the push rod tubes. More air over the cylinder lowers the engine temperature and more air over the pushrod tubes COOLs the engine oil as it passes back down to the sump.

[GAHorn]

The TCM-approved oil temp for SAE 50wt oil is 240F not 250. (Probably a Bruce-typo)
The LOCATION of the oil temp probe is important (per type certificate) so measuring anywhere but the oil inlet (inside the suction screen) is misleading. On the C145/O300 this area will give higher temp indications than other engines (especially if compared to Lycs where they measure it at the EXIT of the oil cooler....one of the coolest locations)..... so our engines might make you nervous...but don't worry. High oil temps are OK as long as not above the limit. (240F with SAE 50)
There is no reason for these engines to suddenly give excessively high oil temp problems unless something is wrong. Most common causes are:
1-Incorrect Oil temp gauge accuracy
2-Leaking exhaust riser flanges and clamps which blow hot exhaust onto the pushrod tubes (the return path for oil from the rockers.)

Cheap way to detect inaccurate gauge: Go to Academy or other BBQ kitchen-shop and purchase cheap BBQ thermometer with long 14" probe. Fly til the oil is hot, land without allowing excessive cooling and plunge the probe into the dipstick tube and take a measurement.
Most common result: Big surprise....the oil is about 50-75 degrees cooler than you thought.
Go fly. Be happy.