Oil and oil pressure.

[Gmg31]

Drove down to Silverstone at the weekend and noticed that when sitting on the motorway at 70mph my oil pressure dropped quite alarmingly. (Renault federal 1560cc ) Had to spend the whole weekend below 50 in order to maintain reasonable oil pressure.  There were several oil specialist at the event and the general consensus is that I needed a Classic 20W50 that would maintain its integrity better.  There were two front runners, Miller and Duckams. I bought the Duckams and undertook the oil change tonight. A couple of interesting outcomes.
When I started her up the oil light went out quickly but the gauge was slow to climb. when I went out for a drive I noticed that the pressure was lower that the previous high but it remained solid and never moved one way or the other no matter what speed I went up to.  I wonder what others find their oil gauge shows and how they move at differing speeds.

[EuropaTC]

I'm on the TC engine so bear that in mind with the following experiences....

In the 80s I used the normal 20/50, either GTX or that green Duckhams stuff. When Mobil 1 came out I went to that, I think it was initially 10/50. Oil pressure stated the same at idle or running and when 0/50 came out I went onto that despite dire warnings from some folks. Make winter starting easier but otherwise no more leaks, no change in pressures.

Fast forward to the 21st century and we either have the choice of "classic" 20/50 or modern full synthetic 0/40 (or 5/40, 10/40).  I did wonder if it would affect hot pressure being 10 down but no, hot pressures are the same.  So it may well be controversial, but I'm not convinced that we "must use" a classic 20/50. Having said that, I'm not brave enough to fill it with 0/30.....

[jbcollier]

Can you give us some numbers for comparison.  The oil pressure was at “X”.  At a steady 70 mph, it dropped down to “Y”.  I know the gauges aren’t renown for their accuracy but it would give us a better idea of what’s happening.

What oil were you running on the way down?

What do you know of the history of the engine?

[Gmg31]

The engine was a 1560 Federal Renault Lotus factory   test engine which  had never been in a car and was gifted to the prev owner by Mr Chapman.  It sat for 35 years in his garage.  When I got it I took the head of and inspected it and its a good engine, I skimmed the head and re seated the valves.  At the time I didn't know how long she had run as a test engine so I used Miller running in oil just to be on the safe side. 

On my gauge the first mark doesn't have a number but I'm guessing its about 25, the second mark is 50 and the high number 100.  During my first 1000 miles the needle was just above 50 most of the time but dropped to the lower mark on the 70 mph run probably about 25.  Since the new oil change she now sits at the 50 mark and doesn't move at all.   

[EuropaTC]

John is the expert on here for Renault so his input will be more relevant than mine.

Unless the Renault is like the old A series and runs at 70psi, I would have thought 50psi when running above 2000 revs was reasonable. If it were a TC engine it would be remarkable on the standard pump !

I've just realised you were asking for numbers in the first post, so the gauges on the Europa (TC engine) normally show 25 on idle, 40+ at anything over 1500rpm when hot. (it hits 60psi cold)  The Elan has much higher mileage/worn engine and normally gives 20psi idle, 40psi on the move and at around 85C it's normal temperature. 

If your tickover is 800 rpm then I'd expect the gauge to show a significantly lower pressure at idle. If it's 50psi regardless of revs I'd be looking for the reason.

Brian

[Clifton]

I read once 10 psi per 1,000 rpms. My 240Z, more than one, never got about 50 psi ever.

[jbcollier]

Clifton is quoting what the Renault manual says: minimum oil pressure is 10 psi per 1000 rpm.  My oil pressure is 60 psi on start-up (cold oil) -- the rating of the oil pressure bypass.  Light duty (60°C sump oil temp) sees it going to 55 at speed and 40 at idle.  Working hard (80+°C sump oil temp) it drops to 50 at speed and 25 at idle.  I run a front mounted oil cooler with an oil thermostat that opens at 80°C.  Even flat out for half an hour sees the oil temp under 100°C.

I'm currently running Penrite Classic Light (20/70, conventional) and plan to try Mobil 1 (10/50, fully synthetic) next as the engine is now broken in.

The stock cooling system is on the marginal side and the little engines work hard.  This means high oil temps.  Fitting an oil cooler is a good idea and high quality oil is an absolute must.

What oil were you running on the way up?

[Gmg31]

Thanks for that JB exactly what I needed.  I was using the Miller running in oil for the first 2000 miles. But can’t remember the grade.  Im really pleased with the Duckams. I have an oil cooler which I didn’t install but might do so in winter.

[jbcollier]

Then I definitely wouldn't worry at all.  Running in oil is not meant for high load situations.