estoma
Well-known member
That is pretty hot. Good quality mineral-based engine oils will start breaking down (change chemically with corresponding detrimental mechanical property consequences - viscosity and lubricity) at around 275 Fahrenheit. (Fully) Synthetic oils are often very optimistically touted to around 450 degrees (flash point) and 500 degrees (fire point) but I would think they would similarly face chemical deterioration beyond 300 degrees. Semi-synthetics might sit anywhere in between.
I would freak if mine exceeded 260 (circa 127°C) on the higher-clearance air-cooled motors or 220 (circa 104°C) on the close-tolerance liquid-cooled ones, including the R18 since it is EURO-5. Just my own yardstick of course. I install dipstick-mounted temperature gauges so that I can correlate their readings with that indicated by the fan controllers - and for configuring controller activation as well. I am not an advocate of infrared thermal guns. Better ones come with their own (limited) emissivity tables, but emissivity is often hard to access properly (and accurately) - see https://ennologic.com/wp-content/uploads/2018/07/Ultimate-Emissivity-Table.pdf. I appreciate that gauges and sensors are ordinarily inaccurate as well, which is why I prefer using two.
Oil temperature is my other reason for using K&P Engineering Oil Filters - the finned, air-cooled enclosure. Not that the R18 will gain much from that, given its recessed oil filter location. Also no dipstick thermometer on the R18 since it is hidden behind a tappet-cover cover. Will need to come up with something else then.
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