200tdi unusually high fuel use

A up all,

My 200tdi def has recently began to use an excessive amount of fuel, way more than normal. Usually I get 230-40 miles per full tank with general driving and occasional towing, now I’m averaging 170 miles per tank. Only thing that I have done prior to noticing the change is a full service and replaced a injector leak off pipe. I’ve gone through the fuel lines looking for a leak. Checked turbo boost which is normal. No more smoke than usual. Engines running at right temps. Brakes are not hot and/or sticking. Any ideas where to look next?
Cheers Ben

I'm assuming you've checked your tires?

Yeah, they’re still there

I took the filter off the other day to add some injector cleaner direct. The filter was only 3/4 full. I bought a new lift pump just in case and the old one did seem knackered. Just been out for a drive and no difference. Performance is still sluggish and when I took the filter off again after a few mins of getting back the filter was still about 3/4 full. Boost diaphragm good and no leaks.

Are you just going by fuel gauge reading for when its empty or are you actually calculating mpg from mileage and fuel added (just in case your gauge is misreading)

I’ve gone off the gauge and how much fuel I’ve needed to fill the tank up. Just refulled tonight (trip meter reading 170mls to a previous full tank) and I’ve filled up 46ltr in a 55ltr tank. So I’ve done 170mls to 46 ish litres. The last time I refulled it was roughly the same amount hence why I know I’m losing fuel somewhere.

That's about 16 mpg, cant see how it can get that bad and not have some form of engine issue (unless it is leaking or being syphoned off by a scallyway)

................Unless you trip meter / speedo is under-reading, are you doing the same journeys each week (therefore the same physical miles) or is it general driving around.

My routes to work vairy as I’m a tree surgeon so no fixed place of work. Fuel tank/cap is locked and like I said there is no visual signs of a leak. I still don’t get why the fuel filter is only 3/4 full.

Any performance issues? Air getting into top of fuel tank OK? No chance of a vacuum? Any inrush when you take the filler cap off?

I think it is normal for the fuel filter to be 3/4 full.

What is your air filter like? I know you said you had it serviced but was the air filter done.

Col

Yes fuel filter unlikely to be totally full. How is the seperator bowl?

It doesnt seem to pick up too well off the line like it usually does as I said before similar to turbo lag/fuel starvation. There was a vacuum created in the tank a few weeks back when I went to fill up but this turned out to be the leak off pipe (1st injector to op) perished and came off. I replaced it and did the service (inc air) and the vacuum/inrush went. My filter doesn’t have a separator just a tap at the bottom for water.

No seperator back by the tank, like on a Disco 1?

Nah, direct. Pick up from tank to lift pump, filter then ip.