I took the camera along but was thinking, I may forget to snap the picture when we get home. Once home my wife distracts me by asking not to lock the car, open the trunk and help me carry in the groceries.

We were on our way home with no traffic on our side of the 4-lane highway. I asked my wife to hold the wheel while I snapped the picture. I was cruising at 40 in a 55 zone, one of my favorite areas to pick up gas mileage.

 

Jimmy,

Thanks for the additional info. and for going to the trouble to post the picture.

I'm getting pretty settled on my understanding of the gauge scale now.

A few further thoughts:

1. I was using 20F per mark as a matter of simplicity and convenience. You calculated 18.3F per mark. I see now that 20F was probably too much.

2. I do not suppose that there is necessarily a reason to think that the number of degrees per mark needs to be a "round" or even a whole number of degrees, or that it would be graduated in F rather than C, but it is convenient to think of it in whole degrees.

3. I note that that a graduation of 18F per mark would be equivalent to 10C per mark.

4. I'm inclined to think that the scale is fairly uniform (i.e., linear) unless or until I get/take some data to define the non-linearity. This would mean that the cold end mark (zero) would represent something in the range of 80 to 110 degrees. I recently read the needle as being on "bottom" (i.e.,
on the edge of the letter, "C") with a dead cold engine and 75F ambient temperature. This would indicate to me that mark zero may be higher than the 80F I estimated previously. I'm content for now to think of the zero mark as representing about 92 f or 33C. Over the summer here in Houston I will surely get the opportunity to read the gauge with morning ambient temperatures in the 90's.

5. For what it's worth, this morning my block heater had brought the needle all the way up to mark 5 (normal operating temperature) with an ambient temperature of 72F.

As I said, I'm well enough settled on all of this for the time being. Summer will give a better fix on the bottom of the scale and may also show whether the block heater can push the gauge above mark 5.

Thanks again for the help.

 

The scangauge usually shows the engine temperature near the same as the outside temperature. I do notice if the weather is warm the engine heats rather fast by the time we drive the 200 foot driveway out to the road.

Still it's hard to guess at the taper on the gauge for the 11 marks. I would think higher temp between the marks near the cold end. Then less temp graduation between the marks near the hot end.

This would allow for quick needle movement toward the hot if the engine overheated.

John, i'm not sure if I mentioned you can shorten your block heater plug-in time as the weather warms. I see Houston is at 60 degrees in the mornings and peak at 80 degrees around 3 pm. Were close to that here in New Mexico but now have 20 to 30 mph winds.

 

Yeah, that would be a good AVERAGE of Houston at this time of year, but it's quite variable. We've had morning temperatures from 40F to 85F in the last couple of weeks.

And, at 80F, outside, I seem to get the bulk of the heater benefit in less than one hour.