Unless you have been keeping careful records your observation that increased fuel consumption is occuring….is subjective….
Valves which are overdue for adjustment are usually too tight…not too loose…. in my experience with new equipment. As the valves wear-in and complete seating they descend into their cavities and valve clearances become tighter….not looser.
In older equipment…once the initial break-in adjustment has been accomplished…. then continued wear usually occurs at the cam-lobes and rocker-arm-contact-point with the valve-stem …which results in excessive clearance and ”may” be heard as “clatter”….. but not likely to be heard in a diesel.
This is why valves that are never properly adjusted from new break-in… often survive well into years as they age…. because the pattern of wear is first reduced clearance, then increased clearance, which tends to cancel each other out….. IF you are sufficiently lucky not to burn a valve after failing to make the first post-break-in-adjustment.
As for your perceived excessing fuel-consumption… I’d recommend you first look for a leak. It’s possible that during operations a leak is dropping fuel on the ground and going unnoticed. If no physical leak is occurring then I’d suspect fuel injector cleaning or injector-pump calibration.
Is the RTV showing black smoke when none was previously observed? If a sudden actual increase were occurring then the exhaust should show black smoke from running too rich.
Maladjusted valves… such as “clatter” from excessive clearance…. would be unlikely to significantly affect fuel consumption anyway…. Fuel consumption is a function of cylinder volume, RPM, and pump pressure/timing.… all other things such as altitude, barometric pressure, and work-load being equal.
It’s very unlikely the average operator/owner would have instrumentation and consistency of work-load to be able to detect a fuel consumption change from mechanical valve issues.…and the relatively low-time-in-operations of the subject engine is not concerning as to piston/ring wear or other engine-wear-friction issues.
Now transmission slippage might be suspicious if you are consistently doing the same tasks…. but if you’re now performing tasks differently than previously…. or have come into the habit of carrying around more junk/heavier loads…. etc etc….
