Hello acy76. At this point, these are the numbers are for the C223's and most likely any other engine that this part number glow plug is recommended for such as the 1.8 Isuzu.....I am setting up a Toyota 2L-T diesel in the next few weeks or months (its a transplant) for a friend and he wants to use the "method" and we will see if similar reads occur.............

I am fairly sure the "method" holds true to any IDI....the actual readings may change with glow plug design and 6 or 12 volt rating........the cylinder temperature relationship should hold true ...........

I do know that a couple of glow plug manufactures have patents on the basic "idea" and some are very old.........some in 2005......

regards,
crossbones