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Sun May 18, 2025 6:27 pm

Once warmed up my oil light flickers, not a solid red. Here is as much info as I can give you:

Using Quaker State 10w-40
Engine is relatively fresh with good compression
Using an external oil filter assembly from CB
Using a WIX oil filter.
Oil sender is new but don't recall the brand.

I have been told by some that I should be Using 20w-50. Others say not needed. I don't like to be just a "parts changer." Any ideas from those with a similar set up or similar problem will be a great help.

Thanks in advance!

Scott

Sun May 18, 2025 8:24 pm

Do you have access to an oil pressure gauge set for diagnostic testing? Can you borrow one? Does auto zone or o’reilly have one on the rental tool list?

If you can lock down the actual oil pressure you have a starting point. We can work from there.

Mon May 19, 2025 7:29 am

Avoid the 20W50, as Rob says a guage screwed in the hole temporarily will tell you if it's time to panic, or that the switch is turning on at a higher pressure than it should.

Or just try another switch.

Do you have a laser thermometer gun?, or a meat thermometer that will fit down the dipstick hole?, a temperature reading when it's flickering can tell you alot too.

Mon May 19, 2025 9:44 am

Is that a combined pressure gauge sender and warning light switch or only a warning light switch?

The combined switch switches at about 9psi, the stock switch at about 4psi.

Both are pretty low, but with a hot well used engine there are times idling where a stock switch would stay off but the combined sender would flicker on.

Or do you have a "save my Bug" dipstick with an additional contact going to the oil pressure switch . They are designed to make the oil light flicker well before the point that anything is wrong, (especially in a bus) by reacting to oil temperature directly.

Mon May 19, 2025 10:43 am

all of the above. I would not use 20w-50 unless you are in a bus in 100F weather out on the highway or climbing long grades - in which case you may need to pull over once in awhile and let the engine cool a bit.

A stock sender will not trip the red light until a really low pressure. The aftermarket ones can set off around 10 pounds pressure and they will flicker at a light, especially if your idle RPM is a bit low.

Mon May 19, 2025 7:37 pm

According to the owner's manual it's normal at idle if fully warmed up. It can happen more if your idle is a little low.

Tue May 20, 2025 12:43 am

have a bias against Quaker State oil. It has been problematic in the past for me in A/C & water cooled VWs. I suspect a lack of anti-foaming agents.

Can't prove it. But Castrol 10w-30 didn't give me fits when I put that in. so no more green bottles for me. That was decades ago.

Tue May 20, 2025 4:52 am

The temperature of the oil is critical here to diagnose where the problem is. Post a picture of your engine compartment too so we can see if the tins and seals are all in place. Lots of guys don't realize how much air recirculation back there effects oil and head temperatures.

Tue May 20, 2025 5:58 am

besides what has been mentioned above:

Bearing clearances can effect this, even on a fresh rebuild

Oil pump clearances…do you know if the gears were flush with the pump face, pump cover gaskets vary and thicker gaskets reduce pressure.

Does the oil pump shaft fully engage the cam? This is something most don’t think of or measure and can result in what you are experiencing.

Tue May 20, 2025 7:25 am

There's one important distinction that you didn't specify.

Is this happening only at idle or even while driving?