Exhaust, oil and cooling ?s

[kas83]

All questions are in regards to my relatively tame 95. First off, I have only put 2600 miles on my truck in 6 months. When should I change the oil? When I had my local job and my 97, 5000 miles was about 4 months, and those were the intervals I used.

Second one is, my water temp gauge is constantly moving, and you can feel the difference in heat output as the gauge fluctuates. Cummins tstat installed in January of this year. I know that keeping a constant temp, and maybe running it around 195* or a little higher will help mpg. Is there a better thermostat that doesn't cycle as much, or a hotter thermostat I can install?

And lastly, I am in the process of throwing together a 35/40 hybrid, 14 cm non gated, and will be installing a set of 215 injectors. With a 3" turbine outlet, is there anything to be gained by putting a 4" exhaust on the truck? This is not an all out performance truck, it's just a daily driver with a little extra power over stock.

Thanks for your input.

 

[9712valve]

All questions are in regards to my relatively tame 95. First off, I have only put 2600 miles on my truck in 6 months. When should I change the oil? When I had my local job and my 97, 5000 miles was about 4 months, and those were the intervals I used.

Second one is, my water temp gauge is constantly moving, and you can feel the difference in heat output as the gauge fluctuates. Cummins tstat installed in January of this year. I know that keeping a constant temp, and maybe running it around 195* or a little higher will help mpg. Is there a better thermostat that doesn't cycle as much, or a hotter thermostat I can install?

And lastly, I am in the process of throwing together a 35/40 hybrid, 14 cm non gated, and will be installing a set of 215 injectors. With a 3" turbine outlet, is there anything to be gained by putting a 4" exhaust on the truck? This is not an all out performance truck, it's just a daily driver with a little extra power over stock.

Thanks for your input.

my rule of thumb is 3 months or 3000 miles which ever comes first.
I can't help with the t-stat, but truck does the same thing when the t-stat opens it drops to 160 or whatever temp it is and the heat is no longer hot. not good for the winter.