Oil Metter

I pull heavy with mine, 215 is normal empty for me, but I'm 44,000 lbs empty.
Then when I'm loaded 220 is normal, then 230 when climbing.
Everything about a modern truck is hotter. The water temp isn't considered hot until 230.

 

Provided That, you're able to understand the INFO the Gauges are telling you... That is...

 

Usually it's a trans temp gauge. The 3 of them are usually clusterd together.

 

I have the same dash as the O.P. , it is the engine oil temp. The transmission one is on the opposite side of the dash, says "Trans" on the gauge and goes up to 350 degrees.

 

If they are both pegging up that high I would be suspicious of a ground problem for the dash gauges instead,

 

All fluids run about the same temps.
Water, oil, grease. Heavy load on a steep grade when its hot, anything over 230/250°f is getting hot. Pyro is another story.
OP is asking if the "gauges reading" 300 is normal. What kind of question is that. Of course its normal! Thats what the truck manufacturer made as the upper most reading before melt down. Its oil meter.

 

Oil temp rule of thumb is 20F hotter than coolant temp.

 

Your reading comprehension is lacking. I said 300+ or - is as high as the gauge reads. Not the op temp.