Oil treatment

[GeoffK]

Hi
Has anyone any comments or views on using Wynns oil treatment. My engine has done 118k miles and does not seem to be using oil. Oil pressure normally 45-50 psi. Runs well. Oil cooler fitted

Cheers Geoff

[Paul Hollingworth]

I've been using Moris's Golden film engine oil which is cheap from TFM, the last I bought was £11 for 5 litres but it's gone up 7 quid now. It's said to have 700 ppm ZDDP (zinc) which is one on the lower classic 20W50 oils. (Who knows how much is enough) I've been supplementing this with STP which is rumoured to be 1900 ppm. Still miles cheaper than buying Duckhams Q20-50 which is over £30 for 5 litres but is 1200 ppm. The STP makes my engine a little less rattly but doesn't do anything for my oil pressure as that's controlled by the relief valve to 65-70 psi. I suppose it may help the pressure at idle but its never below 40 psi when stonking hot anyway.
https://www.tfmsuperstore.co.uk/product ... 5-litre-2/
https://www.classic-oils.net/Oils-by-Ap ... neral-base

[GeoffK]

Would you consider an oil pressure of 45-50 to be a bit low? If so what can be done to raise it?

[Paul Hollingworth]

Yes, I think your oil pressure is a bit low but many B series engines survive for years like that. Assuming your crank isn't worn you can change your big end shells and three of the main bearings in situ by just removing the sump. I ran the engine mounting nuts to the end of their threads then jacked under the sump with a suitable piece of wood to lift the engine enough to get the screws along the front edge of the sump with an open-ended spanner. The others are easy to remove. There is a John Twist video on you tube. I had the head off when I was doing this, but I see no reason why you would have to, just take the plugs out. To be honest you probably only need to do the intermediate main bearings (2 & 4) as they are the narrowest and tend to wear. I also changed my oil pump rotors and relief valve spring.

[Ian F]

Geoff, one thing I think to remember is that it isn't oil pressure per se which keeps metal surfaces apart. I was told this by a tribologist (Google?) so I believed it. It is the shear strength of the oil film I believe.
Dropping oil pressure may be a sign of wear in bearings - increased clearances - but I would agree with Paul, 40-50 psi is acceptable. I am assuming this pressure is at running speeds (3000 rpm or so?) and with the engine hot?
It also may be something as simple as an inaccurate gauge or a pressure relief valve setting.

Ian F

[GeoffK]

Paul & Ian Thanks for your feedback. I am not inclined to change the bearings at the moment - maybe a summer job when the wind and rain have eased of.
The comment that the shear strength of the oil generates the actual pressure sounds very plausible. I am assuming the shear means the ability of the oil to hold together under opposite (shearing) forces rather than than its actual physical strength. Does that make sense? In which case ‘beefing’ up the oil with an additive could improve the shear strength of the oil between the bearing surfaces therefore increase the oil pressure??
The oil pressure, albeit a bit on the low side is fairly constant even after a run of 30 miles or so when the engine has got really hot. Under those conditions the pressure drops to about 30psi at tick over of 750rpm.
I have only had the car for 12 months and only done 1000 miles, so I don’t know when the oil was last changed but looking at the dipstick it looks quite clean and does not feel ‘thin’. I will add the Wynns in a couple of days and see if there are any differences.

How do you reset the oil pressure relief valve?

Cheers Geoff

[GeoffK]

The Wynns has gone in and no noticeable changes to oil pressure except that at tickover (750rpm) the pressure never drops below 45psi and when I touch the throttle it shoots up to 50psi and stays there no matter how many revs I give it. This suggests to me that the pressure relief spring is ‘set’ at this figure and maybe a new spring is needed.
Engine seems a little bit quieter.

[Paul Hollingworth]

I'm not a tribologist but I used to do oil film thickness calculations to size engine bearings using proprietary software. I could give you some bulsh*t about Booker's mobility solution to Reynolds equations and Okvirks short bearing approximation but frankly I never understood any of that. The gallery oil pressure is an input to this calculation and there is an assumption that there is sufficient flow rate to keep the bearings full. The flow rate to do this is calculated. If you have a large clearance, then the more oil flow is required. Oil leaks out of the ends of short bearings more quickly that long ones. Similarly, more viscus oil escapes less easily so requires less flow rate. Missing from this calculation was the characteristics of the oil pump of course. In reality if the pump struggles to meet the required flow rate then the pressure drops. The upshot of this is that your oil pressure should go up if you add a viscosity enhancer like Wyns or STP. The proper solution is to reduce the clearance in your bearings by fitting new shells. The B series was fitted with Vandervell VP2C bearing material. It was a copper-lead base with an indium overlay. At least one of these materials is deemed toxic so consequently it's no longer available. It wasn't required for a low output engine like B series in anycase. Bog standard aluminium-tin would have been fine. When I replaced my shells most of the overlay had gone from the loaded halves. The engine owned up to having done 100,000 miles and I stripped it because it was burning oil, the oil pressure was still fine. I'm running County brand shells now from Israel which I assume are aluminium-tin without any problems, oil pressure still fine.
I think a valid point has been made about your pressure relief valve. It's worth changing the spring and checking you have the shim in there. It's a small job but awkward. You have to get under the car so you need it up on ramps or axle stands. The valve is at the back of the block where the exhaust comes down. The only thing I could get on it was a ring spanner. It's also a b*gger to start the thread to get it back in. You need strong fingers.
Of course you could just have a faulty gauge as has been said. If the engine doesn't rattle, perhaps you are worrying too much.

[Ian F]

Thanks Paul. I don't think I can add anything to this!!

Ian F

[GeoffK]

Hi Paul
You mentioned a shim that is fitted with the relief spring. I assume that if the shim is fitted it would increase the ‘strength’ of the spring by shortening its length by the thickness of the shim This would mean that the valve would open at a higher pressure. If the shim is not there the valve would open at a lower pressure. I wonder if mine has a shim fitted? I think that a new valve/spring/shim is required. Cheers Geoff