On a hot day my idle pressure will sit at just under 2, about 2.75 I guess
On a cold day it'll stay just above 3.0
(That's on an engine with 40k miles on it)

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)