Sounds like the perfect excuse for an "Italian tune-up"  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

designboy wrote:

One last question is where does the sludge blockages go once its blasted through the engine on motorway runs? This is why I thought you might have to open it up to remove it. I'd seen a post on here where someone did - they vacuumed it out! Guessing you dont have the skills to do this with out knowing what your doing too.

You're confusing the two issues:
Decent long runs using top quality fuel and an additive, if you think the engine has been used for only short runs and is likely to have heavy sooty deposits in the combustion areas (piston crown, valves and head space), should reduce the deposits.

Oil sludge builds up in the oilways inside the engine when the oil isn't changed frequently enough or the wrong oil is used and especially if the car is used for short runs only. The only way to get rid of the sludge is to change the oil and if it is very black and contaminated run the car for a week or so and then change the oil again.

Change the oil at half the recommended intervals i.e. about 7k miles not 15k.

Don't use oil flush - most engineers agree it does more harm than good. Only use OE filters and take care when fitting that the spigot is properly engaged before bolting down. Use the correct spec oil and make sure the engine is properly warmed up before draining out the old oil. Oh yes - and be aware there are two sump plugs to remove when draining. They are not re-usable so you'll need to buy two for each change of oil.

Having said all that I had better practice what I preach - just about to change my engine oil this morning! 2008 MY Java Black TDV8 HSE

I must google how to do an oil change then. Guessing its straight forward enough.
I'll do one a year and have LR do the other on the service.