Missing information: how many miles/day (or month) does she drive?
There’s a major difference between driving all over CA to service patients and taking care of patients all within a small town. With that said, the high ambient temps and idle time assure me that this engine is seeing a lot of operation at-temperature, which is really good.
If she’s driving a lot of highway and/or the engine is at operating temperature as mentioned above (easy to do with 100F+ temps), 5kmiles intervals is likely a total waste. If you don’t believe me, send out a sample for analysis. If you like to change the oil frequently for personal pleasure, then by all means have at it. If it’s a chore, then I’d consider extending the interval with the same oil or extending the change interval using a more robust oil, if that makes you feel better.
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As has been said, the cooling system and A/C seem like more important systems to maintain than worrying about engine oil, which rarely causes issues if the level is maintained and the oil changed at an appropriate frequency.
You say you keep up with the rest of the fluids every 30k, so that likely means coolant changes, right?
At that mileage, I‘d have her pay particular attention to the A/C performance and nip any underperformance in the bud before it becomes a costly repair.
