How will I know if I need new diesel injectors?......I'm only getting 20mpg....

[Love my 83 300D]

but car is running well, except when I first start it in the AM. The pickup is slow, but gets better once it warms up.

Any way to increase mpg? I've heard that I should be getting 28 mpg....

I've adjusted the valves, changed filters(by the way how often should one change the fuel filters?) could it be the injectors???

Thank you for any help, I've just bought the thing, It has 312k on it and I've already put in around an additional $1000.

Thanks again for any feedback.

[sixto]

Fuel mileage is highly dependent on driving style.

Expect fuel mileage to decrease with winterized fuel.

There are specific symptoms that indicate that injectors need attention. It's in the archives. Wholesale replacement usually doesn't pay off. It's best to check the system thoroughly - chain stretch, IP timing, delivery valve and seal condition, filter condition, cleaning with Diesel Purge, etc. Even on replacement, I think the balance tips in favor of having a qualified shop clean, calibrate and balance your injectors vs installing rebuilt injectors. The quality of the rebuilt injecors readily available has been questioned.

Sixto
95 S420
87 300SDL