hi everyone, ive just service our mk1 1.8 eunos roadster, it had a slightly high oil pressure before the service, i put this down to old oil, so, old oil out, new oil in, new filter as well, now, the oil pressure is higher, it sits at about 5kg/cm2 on start up and goes to 6 when first driving, then drops to 4-5 when fully warm. on tick over it drops to about 2 - 2.5 kg/cm2 which i take it about normal, what could be causing the oil pressure to rise that far?
any help is appreciated
Sounds normal to me, drive on! 
Mmmm…if that’s normal then you have got me slightly worried. Mine sits around 1kg/cm at idle and runs at 3-4 when warm which is a fair bit lower. Or is that within the acceptable range?
What oil did you use?
Mobil Super 2000 XP 10w40 semi synthetic oil as recomended by mx5parts.co.uk. i thought that the oil pressure should be more like 1-2 when idle and 3-4 when driving.
50 psi when warmed-up and driving is a good pressure. 1 bar = 14.7psi
so what could cause the high pressure, and is it bad for the car?
Hi
I would think an old, thin oil would give rise to a lower pressure than new, viscous oil.
My 1993 Mk I Eunost Roadster is just the same as yours. As taff eunos says…drive on!
MikeC
More likely to be the sender-unit possibly showing early signs of failure if it has only just started to show those figures. I have a low-mileage 1994 1.8 which goes straight to 6 on the guage on initial cold start then as the oil warms up the needle sits half way up, only ever drops to 1.5- 2 bar after a few hours on a hot motorway run.
My 1.6 reads 6 on startup, about 4 @4000 revs once warm and about 2 at idle. 10W40 oil used. I’ve never thought these readings as odd…
so probably nothing to be concerned about? i had images of head gaskets going due to to much pressure and and all sorts of other things. the car has done 122000 miles!!
1997 1.8 manual;
Oil Pressure
With engine at operating temperature, oil pressure should be 15-28 psi (1.0-2.0 kg/cm2 ) at 1000 RPM, and 43-
57 psi(3.0-4.0 kg/cm2 ) at 3000 RPM.
Oil Pressure Relief Valve
Pressure relief valve opening pressure is 50-64 psi (3.5-4.5 kg/cm2 ). Pressure relief valve is located in oil pump
body and is not adjustable.
LUBRICATION SPECIFICATIONS
Material Condition Specification
Engine Oil (1) Ambient Temperature Above -10°F (-23°C) To Over 100°F (38°C) SAE 10W-30
Engine Oil (1) Ambient Temperature Less Than -10°F (-23°C) To 60°F (16°C) SAE 5W-30
(1) Energy conserving oils are recommended, API classification SG", “SH”
It may depend on how accurate the gauge is but that oil is a bit heavy by the book and probably thicker than the relief can handle cold. Mobil suggest 0W40 and Castrol 5W30 both fully synth. Personally I would change it as you don’t want to risk damaging the pump and thick oil won’t splash cool as it should either.
well thanks all of you for your replys, but im getting a few mixed results here. should i change the oil or leave it? and if it is the wrong oil, how can i let mx5parts.com know this
I’d say it’s normal and you can just leave it. The figures you get are exactly like I always got with my original '94 engine. My replacement engine (and pressure sender) always show somewhat lower readings, but not so I’d worry about it. 10W-40 oil is fine.
There is a mountain out a mole hill being created here!
There is a guy who is working on these cars in a professional basis, Taff
Eunos and he has told you to leave it alone. Then there are the amateur mechanics,
myself included in that description and one of them has even told you to change
the oil.
If you are unable to takes Taff’s advice that things are good, you have to
do the following to sort your worrying out no advantage to the car.
Change the oil and filter very unlikely to reduce the indicated pressure
but if it makes you feel better why not say £40.
Then you can replace the oil pressure sensor second hand say £30, new I
guess £100, do not use a modern Mazda one as they are only a switch after say
Then you could take the sump off that is a real pain of a job and change the
oil pump as that has the relief valve if 1 and 2 do not get you the reading
that believe you want. Cost say £300 to £400.
So you no longer have conflicting advice.
Either drive it or waste your money!
What grade does your owners handbook say to use?
OP
It will be fine, leave it be and it will sort itself out.
M-m
Hi Rich and Katie
I have taken some pictures for you. They are of my 1993 Eunos Roadster S-Special 1.8 with 148,000 Km on the clock. I have had the car now about 5.5 years. I always pay attention to the oil gauge because of her age and it has not changed since I bought her. It runs like a dream, as it always has. Below is a record of the service I maintain.
November 2012 90,420 Drain oil & replace with Mobil Super 2000 X1 10W/40 semi-synthetic oil. Replace oil filter. 7,812 since oil change.
So, it is 2,000 miles since last oil change. I use 10/40 because I spend a fair amount of summer if France.
Images 1 & 2 show the gauges immediately upon starting. Cold water, high revs. Image 1 is at idle, Image 2 is at 3,000 revs.
Images 3 & 4 show gauges after running the engine while stationary to get to normal running temperature. Image 3 is at idle, Image 4 is at 3,000 revs.
If you are going to work on your car yourself consider buying one of the many good manuals available, which will identify suggested oils.
If you don’t want to go on the recommended oils from the forum identify the ambient temperatures you plan to run the car in which will point bto the viscosities required. Then choose a reputable modern brand that will conform to current specifications.
Hope this helps and that the images actually do appear, I’m not an expert.
Cheers
MikeC
Nope…Photobucket looks and feels totally different now…can’t get my head round it! If you want the images PM me with your email address and I can mail them to you.
MikeC
I wouldn’t worry about it. I wouldn’t trust the dashboard gauge anyway. If you want to be sure of the oil pressure get it checked with a workshop oil pressure guage. New oil will give more pressure the old oil.