Manufacturers reccommend as little idling as possible.

It takes 30 secs - 1 min on startup to get full oil pressure to the entire engine. That is the longest you should let it idle when cold.

Hot idle is best avoided as much as possible. You can "deglaze" an engine by driving it hard, but it is best not to glaze it in the first place.

If you need to charge a battery - it is better for the engine to go for a short drive - the battery will charge faster too!

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Cheers,
Ben.
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1987 110CSW, 4BD1T
1968 IIA 109 2.25D (172-131). REMLR #244