Auto-RX and Oil Pressure Light

[mdv]

I've been using Auto_rx in my 92 Corolla with 171k on it for the last 500 miles. Recently, when at hot idle, the oil pressure idiot light will flicker or be steady until the rpm is brought up a little. Needless to say, this is very disconcerting.

After a phone conversation with Frank, it's my understanding that is normal in some cars as Auto-Rx also cleans the sending units and causes the sporadic readings. I hope that's the case as I don't want to kill the engine.

Out of curiosity, for the others who have used Auto-RX in high mileage or neglected applications, have you seen this happen on your cars?

 

[W.T.McGlynn]

Tried "Auto-Rx" on my 99 Tacoma
@ 58K on the clock.Ran cleaning cycle for 800 miles.Have not had any oil pressure light flicker or come on.I would guess the oil pressure
if anything should be better,but that is only a guess.Good Luck & Stay KOOL......

 

[Drew99GT]

I'd undo the electrical sending unit and install a mechanical/test sending unit and read the actual oil pressure just to make sure. It's real easy on Corolla's; the sending unit is to the left of the oil filter on the block. Also, how low does your engine idle? My 94 Corolla will flicker the oil pressure light if the rpms drop below 500 rpm on occasion when the engine is real hot with the A/C on. Specified idle rpm in my Haynes manual is 700 rpm with a manual transmission

I've inspected the idle air control valve and it's fairly gummed up as I recently cleaned the throttle body and intake manifold.

 

[Toyota Steve]

Autorx won't change the oils viscosity. However, if you're cleaning crusted up, burned on oil from places like the crank fillets ,and top end pressure galleys, then your oil pressure will go down. Just like cleaning the plaque out of blood vessels is to lower blood pressure, the result of cleaning the pressurised oil galleys in a crudded up engine will also lower the pressure. Toyota guages aren't the best, in fact any consideration of what they show and reality is purely coincidental. A direct pressure reading guage is the right option. If in fact the pressure is somewhat lower now, just bump up the viscosity, and know the autorx is allowing the engine to now get oil to where it was always intended to be... Steve

 

[Pablo]

Toyota Steve wrote:

quote:

---

Toyota guages aren't the best, in fact any consideration of what they show and reality is purely coincidental.

---

TOO funny!

I must agree with Steve and the others. More of an cleaning effect than anything.

AutoRx may change the viscosity a tiny bit. To say 0% change wouldn't make sense, I mean you are adding 12 oz of a substance that does have a bit different viscosity than your base oil!

Speaking of base oil - that's the key here - when I ran my second dose of AutoRx I used Walmart SuperTech 15w40 - boy does that stuff thin out compared to Amsoil 15w40.

 

[mdv]

Drew99GT: This is a base car, no tach. When I first noticed the light, I bumped up the idle anyway. I didn't see the light for about 50 miles then it came back. I may just have to bite the bullet and put a gauge on it. This is a winter/beater car for me so I was trying to keep expenses to a minimum, but I don't want to cause an issues with it as well. How do I know what the thread size is for the sending unit if I buy a gauge? I've never installed one on a Japanese car and the last one I did came as part of a kit for that application.

Toyota Steve: Thanks for the explanation, that makes sense to me. (As a side note, I work at a Toyota dealer right now, and have been wondering why the oil pressure gauges on the Tundra's show a low/normal reading before the coolant is warm!) I think this engine was fairly neglected before I got the car. I drained the Auto-Rx a tad early and filled the crankcase with 10W-40 instead of 10w30 and am still going to run this to 750 miles and add the second bottle per Frank's reccomendation. I still have the light when the engine is hot, so now I'm thinking the problem is just a light issue and not because the oil is too thin or has no pressure.


Thanks everyone for your input

 

[Terry]

MDV, consider the pressure guage as the answer to the question.

Worst case:
Be prepared for the possibility that the mains are worn so much in 171K the actual oil pressure may be low due to to much clearance or the pump is severly worn from impacted goop .

Best case:
Most probable scenario is the sending unit with a piece of carbon floating in and out of orifice.

Pabs, Auto-RX tested Vis @ 100 C is 7.1 cSt or SAE 20w.

ToyoSteve has the correct analogy IMHO on the engine and sending unit.

Let us know what you find !

 

[mdv]

Thanks guys. Hopefully it's not worst case!

For the record, the oil is Chevron Supreme. I may be going to Amsoil after the Auto-Rx app is complete. We'll see.