Remember that most of these engines worked fine for 30 years with no oil filter at all I feel all of this fuss about filters is 99% engineering ignorance .
It is very rare for a mower filter to be dirty enough to trip the bypass even if it has never ever been changed
I have had some cubs come in with the dirtiest oil I have ever seen, burn't to treacle yet the filters happily passed the oil and still did not create enough back pressure to trip the bypass.
As for oil coolers, well they were all the rage when I was young on motorcycles because RACE bikes had them .
Most of them actually cause damage to the engines by preventing the engine oil from getting to full operating temperature .
Small engines are fitted with coolers if they are going to be used in equipment that operates for very long times continiously like in skid steers , generators & compressors
Unless you are a commercial mower and mow 25 acres in a single session then again the oil coolers are potentially doing more harm than good unless you fit a very expensive one with a thermal bypass valve .
When I was a spotty faced teenager thus automatically knew better than the engineers at BSA I fitted a big oil cooler to my A10
I took it back because I was sure it was defective because it never got hot & was bypassing all of the oil
After the 2nd replacement, the distributor asked me to bring the bike in
He fitted a temperature gauge to my oil tank and asked me to record the temperatures .
In 3 months , it never got above 72 deg C
Full oil temperature is 80 C which is what the bypass valve is set to .
I learned a lot that month and where possible have always fitted some sort of thermometer to my oil tanks and yes the oil rarely ever gets above 85 C no matter what the air temperature is or how much I am abusing the motorcycle
