Morning everyone!

1997 XK8 convertible; 140K

I took her in for an oil and filter change at one of the oil in a box places near me.
They put in 7.7 quarts of Mobil 1 synthetic and replaced the filter ( they told me it was a Jag spec filter).

The issue I'm having is that whenever the car gets to normal operating temperature, the oil gauge and the red dash "low oil pressure" light comes on when at idle and anything below 1000 RPM. Anything above this RPM and when driving moves the needle back to normal. No other signs or symptoms present.

I would appreciate any help you could provide. I await your responses!
Thanks in advance

Nick

 

What viscosity oil did they use?

 

 

They used 5/30 Gus

 

I would not disagree with the 5w-30 but I do not use it I use 10w-30 in my 99. It could be that the transponder for the oil pressure is failing and not sending the right information. I should also note that both the oil and temperature gauges in the xk8 have a narrow window between good and bad so it may not be as bad as you think however, you need to be sure. You need to check the actual pressure at the transponder by removing it and installing an oil pressure gauge and see what the true pressure really is.

 

 

If I recall correctly it is located at the fuel filter. If you do this be sure to check the thread of the pressure gauge before forcing it in I had a hard time finding the right fitting for it. You do not want to screw it up..

 

Just to be pedantic ............ moi ?? Never !!

The oil pressure transducer is an on/off switch so the gauge is as much use as a chocolate teapot - you might as well just have the little light.
Steve's (Jagwrangler) RealGauge adds a "proper" transducer and the necessary electronics to convert the gauge into an accurate instrument.

My guess it that you have a faulty transducer or a wiring issue, but don't gamble on oil pressure - it's what stops your engine (motor) from becoming an expensive lump of scrap metal.

 

Just to be pedantic ............ moi ?? Never !!

Yes - you DO want to screw it up, but not with the threads crossed

 

The oil pressure transducer is located at the oil filter, not fuel filter. I'm sure that's what Gus meant to say. It would not surprise me to find that the pressure is low enough to cause the light to come with that many miles. I used 10W40 in my 97 and according to the Realgauge I had 12 lbs. at idle and 50 at 2000 rpm with a warm engine.

 

Yes the oil filter. Dam my age is showing..

Gus
www.jagrepair.com

 

 

Yes it is mounted at the oil filter. First check the lead on it they may have moved it when they installed the filter.

I made my last trip to one of the oil change shops when they first left the oil filler cap off twice and second poured a quart of oil all over the intake manifold and I did not notice until smoke was pluming out from under the hood and car. Three strikes and you are out!

Check your PM

 

First verify that you really did get a genuine filter with the check valve.

Second, the oil pressure sender (actually an on/off switch) near the oil filter is a cheap part to replace.

Third, if that does not fix it, then a inspection of the of the oil sump is in order (ie; drop the oil pan). They can get clogged with debris from the plastic of tensioners and chain guides disintegrating. I assume you have replaced the secondary tensioners with the mileage you have, this could be a sign that the other plastic bits may need attention.

 

 

I would drain what may be 0w-20 Mobil One oil out right away and put in 10W30 or 10W40 conventional oil before taking anything apart. Leave the filter. The engine is designed for, and the manual recommends conventional oil.

That 0W20 or 5W20 synthetic oil has the viscosity of kerosene and may be the problem at low RPM.

0W20 syn. is whats in my wife's 2017 Rav-4 and it scares me. When it's off warranty I'm using 5W30.

 

a lot of these places use bulk oil and it might be stocked for the newest cars with the 20 viscosity. perhaps they used the wrong oil and or lied about what they used. it is a simple matter to change the oil and see if your problem goes away. everything that is happening says low viscosity.

unless you know the people who work at these oil change places very well never use them. many cars have been damaged by the actions of these places.

 

Really now, surely this debate is over. Blaming synthetic oil for low oil pressure is reasoning less reliant on science and much more oriented toward anecdotal hearsay or witchcraft.

Using the correct viscosity of a synthetic oil in any IC engine, vintage, modern or in between will never cause low oil pressure, or otherwise damage the engine. To suggest otherwise is to disregard both science and the obvious reality of the millions of cars of every vintage now using synthetic oil without any problems.


^^^^^^^ #1
if the person working on your car is making minimum wage, then it's reasonable not to expect much in the way of quality service

Z.

 

Zray, manufacturers specify low viscosity oil for only one reason: CAFE, Corporate Average Fuel Economy, in the States. Low vis synthetic oil adds on average 1 mile per gallon to to fuel economy. His car has 140,000 miles on it. The main and rod bearings probably have increased clearances and may be bleeding off oil pressure at idle. I am suggesting a simple change of viscosity to see if the oil change is the problem.

 

I'm in complete agreement with you on the viscosity. Put in the weight of oil called for in the manual for your climate, and in regards to the oil pressure it shouldn't matter whether a synthetic or conventional oil is used.

But yes, change the oil ASAP and don't go back to the place that put in the current oil.. All signs point to them being incompetent.

Z