High oil pressure after oil change....??

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That's not rust, it's Canadian patina...
Nov 11, 2005
~Kingston, ON, pero soñando de Panamá
Had the oil changed today in my '76 40 I would normally do this myself, but didn't really feel like lying on the cold ground today. I had 5W30 put in - not sure what was in there before, as I had never changed the oil in this truck before. (only had it a month) Before my oil change I was running about 1/2 way between the two ticks on my gauge, slightly on the higher side. That seemed normal to me - mid range on the "in range" of the gauge. Now I am running right at the second bar or the top of the "in range" I would have thought that going to 5W30 would have lowered the pressure in the cold - was I assuming backwards?

Also noticed that my temperature is now running slightly lower (this I can understand a bit more as the oil is doing a better job of lubricating the engine) Before I was at the lower of the two ticks, now I am about 1/8" below it. I still seem to have heat from the heater, but it seemed kind of odd for it to drop that much.

Am I missing something here or is there something I should be checking out.

Oh, I did see the dipstick when they changed the oil, it was bang on level.. (my first thought was too much oil) They said they put 7L in.......

Any thoughts would be appreciated.

Better flowing filter?
first of all, many say not to rely on the stock gauge.

mine runs at about the same spot on "fresh" oil. after it has been in service a couple months it will run anywhere from center of the "ok" range to just above the lower end of the ok range.
The old oil could have been highly diluted with gasoline. By putting fresh oil in it's now as thick as it needs to be. The oil is probably also doing a better job of cooling the bearings which helps explain the lower temps. You might want to keep an eye on it to make sure the oil isn't getting diluted by fuel. Or it could have been as simple as the filter was plugged or some other reason the motor couldn't build pressure.

Are you sure you werent low on oil before you had it changed?
Better flowing filter makes sense....

Why would my oil get diluted with gas? (blowby?)

Engine seems to run fine - and the same as it did before, other than mentioned items

Not really relying on the gauge, but just wondering why there was such a difference.

Not sure about oil level before, it was checked about 3 wks ago, but not by me.
I'm running an Autometer mechanical oil gauge in my 40 and with that I have a more accurate reading of the oil pressure in the 2F. With fresh oil and a cold engine at anything above 1k rpm the gauge will read 65 psi. After the oil warms it will drop down to 60 psi. Warm fresh oil at idle will give a reading around 50 psi. Now after 3500 to 4000 miles the pressure at idle will drop down to about 40 psi, but I still get the 60 psi reading at anything over 1k rpm. So yes, old oil may give a lower reading.
MrMoMo said:
Why would my oil get diluted with gas? (blowby?)

A bad fuel pump is the most common reason. The carbs will also leak down into the manifold after shut down too if they're in need of a rebuild. Fuel will also build up if the motor is running too rich as well.

zebrabeefj40 said:
MrMoMo said:
Why would my oil get diluted with gas? (blowby?)

. Fuel will also build up if the motor is running too rich as well.


the others are quite possible, but running rich is what i would look at first.
Diagnosing oil pressure problems without an accurate gauge is a waste of time.
Not sure how cold you are, but 5w30 is generally too thin for an F-series engine.

I would also diagnose the lower temps separately from the oil pressure issue. Reminds me of the first oil change I did on my Cruiser many years ago, and the same thing happened. Was puzzled about it for a few months until I realized the thermostat had stuck open at the same time. Ended up being just a coincidence...

Just my humble opinion... :)
I am only planning on running 5W30 for the winter - it can be pretty damn cold here. (-15C last night) I was a bit concerned that 10W30 would not start lubing the engine fast enough with a cold start.

Also noticed that my rad cap was making a very slight bubbling/air leaking noise after shutting down (only heard with the hood up, and only found by "earing" around) - could a leaky cap cause my temp to go down?
I used to feel like you did, Bruce, and ran 5W30 in the winter. I gave that up a few years ago. I was running 20W50 this winter, until I changed to 10W40 last week. My wife was driving the '40 the last couple of months and made the point of saying how easily it started (pull the choke and one twist of the starter) even when it was -20F (-29C) (stock starter)! All that thin of oil will do for you is help reveal your leaks.

The gurgling you hear when you shut down is normal.
What is the toyota suggested oil weight for a 2F? (or MUD suggested?)

Temp seems to have come back to normal, oil is just a hare lower than it was - I'm happy!

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