OK. Since I have reached the age when I can no longer trust my memory 100% I retrieved the manual from my 2010 Kia Forte. NORMAL MAINTENANCE SCHEDULE-QUOTE:
“Where both time and mileage are shown, the frequency of service is determined by whichever occurs first”.
Engine oil and filter: “Replace every 7,500 miles or 12 months”.
Most people don’t know that oil gets contaminated with moisture just sitting in the oil pan for extended periods of time. That’s the reason for the annual oil change.
Not a heck of a lot of condensing moisture in the crankcase just sitting. I’ve drained engines that sat by themselves or in vehicles for years and not found any detectable water. However, low mileage over a year often means lots of short hops and thus cold operation. This kind of operating mode produces more condensate and combustion gases blowby and the engine does not get hot enough to boil off the moisture. The oil becomes acidic and eats away at everything but mainly bearings. This is considered severe conditions and the change schedule reflects that.
Especially when that low mileage is on a plug-in hybrid when the engine only starts when the battery needs it to.
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