Oil

Sounds like a good deal Austin, pity it's the wrong grade for a pre-serpentine V8. ;-)

20W50 is the correct grade for a pre-serpentine v8 with the old style oil pump. Marketing forced dictated a change in recommendation by rover, but there were no mods made to the engines to tighten up production tolerances - it is designed to pump a heavy oil in volume, not a thinner oil at pressure.

15w/40 is not thin. The specification is a good one and is what is known as a multifleet extended drain Super High Performance oil. Not a synthetic but superior in performance to many synthetics.

Huw

15w40 may not be thin but it is not as thick as 20w50 as required by V8's.

David LLAMA 4x4

As long as the oil pressure does not drop off the scale when idling and it is not consumed at an accelerated rate then the difference in viscosity is of no consequence.

Huw

That's as maybe, BUT it's the wrong grade for a pre-serpentine V8, and will result in premature rear main bearing and cam shell wear. (Trust me, I've stripped and rebuilt enough of them!) You could also put it in a Ford Zetec engine, it meets all the spec's, BUT your valves would gum and stick because it's the wrong grade. I could put it in my BMW 330d, it's the right grade, BUT it doesn't meet the spec and premature engine wear would result if I left it in there for the normal change interval of 14,000 miles! You need to put an oil into an engine that is suitable both in specification and grade, not just one or the other.

But the later engines call for 10W40 in the LR handbook. My disco always ran 10W40 without either problem. That was a serpentine though

- when did they change the oil pump?

Well I just went and bought some Castrol Longlife 11 oil for the wife's BMW

330i...£39.99 for 4 litres. Thought I was seeing things when she rang it up.

Well now, the BMW engines fitted to Range Rover calls for the same oil when fitted to a BMW but no mention is made of it in the Range Rover handbook which specifies [only the need for] ACEA A3 for petrol versions and B3 for diesel engines. These are the same engines fitted with the same computerised service interval monitor which results in approximately the same mileage drain intervals as in a BMW car. My diesel RR version needs changing at about every 14500 miles. The viscosity specified as suitable for the UK BMW engines include anything between 5w/30 to 10w/40 including 10w/30 and 5w/40 of course. In fact there would be no problem with A3/B3 0w/40 viscosity [such as Mobil1 0w/40 for petrol engines but no other viscosity of Mobil1] although this one grade is not specifically mentioned in the handbook as a suitable grade.

There is a wide range of oils commonly available which meet these criteria without costing an arm and a leg.

Huw

On or around Tue, 19 Apr 2005 13:31:51 +0000 (UTC), "Badger" enlightened us thusly:

yeah, I know. Trouble is, it's not easy finding decent quality 20W50, or not hereabouts. I've been running this one on Castrol GTX "for high mileage engines", which it seems OK with, and which IIRC is 15W40. I did have some

15W50 for a while, but it was crap oil, and worse than decent 15W40. At least the modern stuff has anti-sludging properties, so it's not all bad, and this Q8 stuff says it's designed to resist cam wear, which ought to be helpful.

'ere, that's a point. 3.9 cam into a 3.5 hotwire: good, bad, or indifferent?

Yes, the pump design and the tolerances within the engine.

WRONG! Pressure will be maintained at the pump relief valve (and gauge, if one is fitted) but this is not a true representation of what is happening within the rest of the engine. Every bearing surface is an orifice, the thinner the fluid is then the greater the flow rate across the orifice for a given pressure. As we are talking dynamic pressures not static, the pressure beyond that orifice will be lower than before it, this repeating through the engine until there is virtually no pressure (or flow) at the rear main bearing! The firther away you go from the pump outlet, the lower the oil pressure becomes at each successive bearing, amplified by the use of a thinner fluid.

Same cam, I think mate. AFAIK it was only the flapper type 3.5 that had the totally different cam profile. If I get a chance, I'll check the part numbers.

Nope, it's dear stuff. Ought to be Castrol SLX Longlife I though, not II, that's a VW spec.

Does the Rangie book call for just the basic spec Huw, or does it say that the oil must meet the Longlife criteria as well? I wouldn't dream of putting an oil in my 330d that didn't meet the Longlife I spec, based on the potential wallet-destroying properties of the potential repair bills if it all went pear-shaped. Please tell me of the other oils you know of that meet the Longlife I spec other than SLX and Mobil1, would be handy to know.

ETC6099 3.5 Efi ETC8686 3.9 Efi

Richard

On or around Wed, 20 Apr 2005 08:02:04 +0000 (UTC), "Badger" enlightened us thusly:

True nuff. Mind, the handbook for my (H-plate) one lists the thinner oils as well, but the really thin ones have temperature restrictions. It's rare that it's hot enough in this country to really need the "50" bit, I reckon - plus, decent quality "40" has a chance of staying in grade when up to temperature, and I suspect that the crappier "50s" may not.

On or around Wed, 20 Apr 2005 08:31:24 +0000 (UTC), beamendsltd enlightened us thusly:

's more about the cam timings, though - the early 3.5 and the 3.9 have identical profiles, 2 degrees different in timing, IIRC.

Your last sentence carries a lot of truth in it Austin, especially the bit about crappier oils, however if I were running a thinner oil than 20W50 I'd fit an MGBV8 pressure relief valve spring to up the pressure by 15psi or so (tested with a gauge, not believing the std pressures as quoted anyway!) simply to ensure an adequate flow to the rerar mains.

It's a long time since I was taught anything about viscosity, but there's something which feels odd about this...

[thinks]

I think that the critical aspect is the pipework between the orifices, and the total possible flow. Pressure is a secondary effect here. The pump doesn't shift any more volume with a thinner oil, while each orifice can pass more oil. So there's not enough oil being pumped through the system to meet all the demands, and the differences in the pipework, distance and size and such, decide which bearing gets what oil there is.

Is that right?

If you could pump more oil, it'd be different.

I expect the design of the oil passages in an engine is very important, so that the more distant bearings still get oil.

Yes, the early 3.5 carb and the 3.9efi are same profiles but 3.9efi is 2 degrees advanced. 3.5EFI rangie is a totally different profile. Richard, do you have different cam part no's listed for rr3.5efi and disco

3.5efi? Badger.