I’ve been looking around to find the best oils and fluids for the P5B, as (not surprisingly) most of the products the 46 year old Handbook recommends aren’t around any more. So that I don’t forget, and because this may be useful to others, I thought I’d document it here.

The image above is taken from the very impressive website petroliana.co.uk (permission granted) by Alan Chandler, which documents Alan’s collection and restoration of many petrol/oil-related artefacts through the history of motoring. The site is well worth a visit.

Now, back to Rover P5 and P5B oils and fluids…

Engine Oil

The original Rover P5B manual suggests numerous 20W50 oils, including Castrol GTX which is still widely available, but here’s a very useful thread on the P5 Club Forum.

Seems there’s concern over the amount (or lack of, to be precise) Zinc in modern oils, and that may be causing premature wear to classic engines. This includes Castrol GTX, the modern version of which is very different to it’s 1960’s formulation. Having looked at the content of various oils, my choice would be Penrite Classic Light. This is a 20W-50 oil with a high Zinc content. Penrite also have a very handy product finder for classic cars.

This is available from Classic Oils in Aylesbury.

Automatic Transmission & Power Steering Fluid

The original manual recommends Castrol TQF, amongst other makes. Castrol still make TQF, also available from Classic Oils in Aylesbury. The P5 Club Forum has this handy thread on transmission oils. As far as I can tell the modern TQF is very similar to the formulation in the 1960’s – certainly I can’t find any concerns about it on the web.

There is plenty of concern over ‘Dexron’ type fluids that were specified by GM, as they contain friction modifiers which help to smooth out the changes on boxes that were designed to be used with it. The Borg-Warner 35 that the P5B uses wasn’t designed to use it, and it can cause slip and other problems that can damage a P5B gearbox. I’ll stick with Castrol TQF while it’s still available.

Brake & Clutch Fluid

Seems this is the easy one – any DOT4 fluid should be fine.