My 96 with 83000 miles won't start if I haven't plugged it in when the temp goes below 40!
The red and green lights under the mirror start to alternately flash and the check electronics message comes on.
I tested it with an OBDII but it said NO Codes.
I changed out the K40 but that didn't help.
I've been using Castrol 20-50 in both cars and the 87 starts just fine no matter the temp without being plugged in.
Car runs great otherwise.

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Lee C.
87 300 TD 225000 k
96 300 D 82000 k