Oil Pressure.

[bian]

Hi. I have a 1985 C reg Excel. When first stsrted oil pressure is 3 - 4 , but once hot and idling it drops to 1 or a little below (but needle wavers a bit). If I press the accelerator it will go back to 3-4, same effect when driving - around 25mph drops to 1 push accelerator to 50 mph and goes up again. Is this normal, faulty dial, faulty oil pressure switch ..... or me being paranoid!

[Grant H]

The Owners handbook for a non SE (normal running conditions) lists 0.34 Bar at idle, 2.4 Bar at 3.5K and 3.1 Bar at 6.5K. The oil pressure is used to confirm the engine has warmed up. What you describe is as expected, that is the idle pressure is low when hot.

[bian]

Many thanks. Moment of alarm over and heart rate back to normal...

[CHRISYD]

Not too sure about needle wavering tho. what oil type is it? 20/50, 15/50 etc.

[bian]

Hi. Its 20:50 , new Comma.
Needle waver is very slight
Thanks.

[bian]

Forgot to say, I'm in Andalucia, souther Spain, very hot - but that shouldn't make a differance should it?

[AndyC]

Was that just to highlight how lacking in heat the UK climate is?

If it's a hot environment that ideally use a 60warm rather than 50warm oil (so 20w60 or 10w60) as that will be thicker when warm than your current oil. The cold rating will not matter, so either 10w10 or 20w60 will be fine as you will not be bothered about very cold starts. It should hopefully increase the oil pressure but more importantly give a thicker protective coating on the moving parts at the higher temperatures your car operates in. It's not something i'd say you should rush out to change to, just try and get the 10w60 or 20w60 for the next scheduled oil change.

[CHRISYD]

Hi. Its 20:50 , new Comma.
Needle waver is very slight
Thanks.

Thats fine then. Try cleaning the oil pressure switch connection just to make sure. When the needle does flutter next time give dial a gentle tap and see if it makes a difference.

[Excel_Propshaft]

let me give you a hint

there is a O-ring on the distributor shaft to seal it against the oil pump.
It is placed on the sucking side of the pump.
If its getting old, it can let air pass by in the suction area of the pump.
As with higher revs, the suction "vacuum" increases and let pass air by this O-ring thus let dropping the oil pressure.

[Lotus-e-Clan]

I've steered clear of the Comma brand, mainly due to my own ignorance about the quality, but I suspect it's cheap for a reason.

Anyone on here have any positive experiences with Comma engine oil? Happy to be put right on the quality.

I'd second the 10/60 for properly hot climates, but steer clear of it when the ambient temps fall bellow 7C (best avoid single-figure ambients all together). I ran fully synthetic Castrol 10/60 in my Nicosil SE 912 for about 6 or 7 years and didn't change it often enough. Piston slap when cold became more and more noticeable -especially as the oil ages and degrades - old , degraded (thickening) 10/60 would slap at 15C ambient! But the slap still disappeared with old 10/60 when the engine warms. i now run Valvoline Racing synthetic 5w/50 with no piston slap on start-up unless it's very old and cold.

[DavidOliver]

Hi bian. Here in Andalucia during the summer with a good oil, preferably synthetic as it breaks down at higher temperatures than non-synthetic, it is more important to ensure clean radiators, coolant, radiator air ducts ( these often get knocked off).
Our engines run at 100ºC water temperature, so an extra 15ºC air temperature in Andalucia should be handled by the coolant system, particularly as I doubt we drive around here at full bore when engine heat produced is maximum.
A common fault for cooling are casting burrs on the water pump volute, easy to smooth out.
The oil filter needs to be Lotus compliant, non-return valve and not pressure reducing.
On engine oil change it is worth considering lifting the cam covers to remove all oil and on saddle type covers you can check valve clearances and renew cam cover gasket sealing.

I use Castrol Edge 10/60 and Lotus oil filter.
I also have a mechanical oil pressure guage to ensure direct pressure readings, no loose wires or connections. What you see is what you get.

Dave the cog.

[CHRISYD]

I've steered clear of the Comma brand, mainly due to my own ignorance about the quality, but I suspect it's cheap for a reason.

Anyone on here have any positive experiences with Comma engine oil? Happy to be put right on the quality.

I'd second the 10/60 for properly hot climates, but steer clear of it when the ambient temps fall bellow 7C (best avoid single-figure ambients all together). I ran fully synthetic Castrol 10/60 in my Nicosil SE 912 for about 6 or 7 years and didn't change it often enough. Piston slap when cold became more and more noticeable -especially as the oil ages and degrades - old , degraded (thickening) 10/60 would slap at 15C ambient! But the slap still disappeared with old 10/60 when the engine warms. i now run Valvoline Racing synthetic 5w/50 with no piston slap on start-up unless it's very old and cold.

I must admit i only use Decent brand oils in my lotus although ive used comma or similar in my everyday cars with no problems. I think the cheaper oils dont "last" as long protection wise as Quality oils so i always change the oils sooner than i might with the better oils.

[Skyedriver]

Wasn't sure whether to tag onto this thread or start anew but here goes.
Bought the car 6 days ago, oil pressure looked about right when I drove away but halfway home the gauge started to read what I would say is high. ie it's reading 5bar on a 5bar VDO gauge, it'll drop slightly at tick over when hot to about 4 bar. Not running but the ignition on, the gauge reads about 1bar!
The car reputedly had a service late last year and has been used very little since. Oil looks clean and filter has "Lotus" on it.
The obvious answer is a faulty switch or gauge but of course it could be a blocked pressure relief valve in the engine or the bypass in the filter (?!).
I'm thinking I'll replace the filter and drop the oil anyway but I'm considering checking the pressure with a capilliary type oil pressure gauge which should be more accurate. Has anyone any recommendations for a gauge and where to connect it to. It's not going to be a permanent fixture, just temporarily sat in the engine bay.
Thanks in advance.

[Alan_M]

Wasn't sure whether to tag onto this thread or start anew but here goes.
Bought the car 6 days ago, oil pressure looked about right when I drove away but halfway home the gauge started to read what I would say is high. ie it's reading 5bar on a 5bar VDO gauge, it'll drop slightly at tick over when hot to about 4 bar. Not running but the ignition on, the gauge reads about 1bar!
The car reputedly had a service late last year and has been used very little since. Oil looks clean and filter has "Lotus" on it.
The obvious answer is a faulty switch or gauge but of course it could be a blocked pressure relief valve in the engine or the bypass in the filter (?!).
I'm thinking I'll replace the filter and drop the oil anyway but I'm considering checking the pressure with a capilliary type oil pressure gauge which should be more accurate. Has anyone any recommendations for a gauge and where to connect it to. It's not going to be a permanent fixture, just temporarily sat in the engine bay.
Thanks in advance.

You can buy relatively cheap universal oil pressure test kits. To connect remove the electric sender near the starter motor and screw in adapter.

[MetBlue]

. reading 5bar on a 5bar VDO gauge,

My gauge is scaled 0-7 bar. I assume the sender and gauge need to be matched? Will be interested to see what an independent gauge reads.
Check also you have a good electrical connection at the pick up. Need to check mine, as at low revs, gauge jumps around (flicking) and on occasions jumps to full scale end stop, but once engine is on sweet spot, gauge sits rock steady (water pick up was exactly the same until I tweeked the spade connector. Now it's just a steady read).

Tony