Agree on 5W-40 being too thin but I used to run 15W-40 in mine and never had a death rattle from the bottom end or a flickering oil pressure light. When I had my engine reconned, the builders recommended 10W-60 fully synthetic so that's what I've been running in it since. Not cheap (although you do get the regular deals from Euro Car Parts so if you buy it at the right time you can keep the cost down) but it seems to do the job. Admittedly, that is in what is effectively a new engine though.
At 140k it isn't excessive, mine had 287k when I decided it really did need a rebuild. While you've got it apart, drop the sump off and give it, and the pickup strainer, a good clean. If it's been neglected you'll probably find a lot of sludge in there. If funds will stretch to it, a set of oil pump gears and ARP head studs instead of stretch bolts too. The problem with the stretch bolts is unless you buy genuine Land Rover ones, and they are still made to the same spec as the originals, you've no way of knowing if they will stretch too much, too little or just shear off! If it's got a Britpart oil filter, bin it and fit something like a Mahle, the Britpart ones don't have a non-return valve so the oil can drain back to the sump when left.
As for the original overheat, my money would be on a partially clogged radiator rather than a stat.
Peterborough, Cambs
- '93 Range Rover Classic 4.2 LSE, sold
- '97 Range Rover 4.0SE, in Oxford Blue with a sort of grey/blue leather interior sold as two is plenty.....
- '96 4.6HSE Ascot - now sold
- '98 4.0SE in Rioja Red
'98 Ex-Greater Manchester Police motorway patrol car, Range Rover P38 4.0, in Chawton white - the everyday car
All running perfectly on LPG
- Proud to be a member of the YCHJCYA2PDTHFH club.