# Oil pressure problem after change to synthetic.



## Icebreak (Jan 16, 2006)

I usually change my own oil but before the holidays I was short on time and let a Firestone dealership do it.

I see on the receipt that they used synthetic oil and this truck (Dodge V6 Dakota) has always used non-synthetic.

Right after they did the change I started noticing that the oil pressure guage would drop to zero intermittantly. Sometimes not at all for a few days. Sometimes two or three times a day for a few days.

I suspect they may have not filled the filter before installing and that I have a bubble of air wandering around.

Not liking any anomolies in my vehical, I started thinking over the last couple of days the type of oil may have caused a problem.

Any engine savvy people have ideas or opinions?

Thanks ahead of time.


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## Christoph (Jan 16, 2006)

I would check the wires going to the pressure sensor first.I can't imagine this to be a oil viscocity issue.
C


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## raggie33 (Jan 16, 2006)

very good point perhaps the oil jockey hit the wire there usaly one wire near the oil filter well the ones ive seen where


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## Jumpmaster (Jan 16, 2006)

I have the same engine in my 2002 Ram and just switched to synthetic on Saturday. Haven't noticed any drop in oil pressure, so far.

JM-99


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## Lightmeup (Jan 16, 2006)

Yeah, I've heard of this before. I was told it's not a good idea to switch to synthetic if you've been using regular oil for awhile. I can't remember the reason right now though.


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## Icebreak (Jan 16, 2006)

I think you guys are on to something. Truck runs perfect.

I know this shop does this kind of work all the time. They are in the business district and have a good rep. But still, it's a Firestone dealership. Not one of the more expensive shops I've delt with that have those perfectionist type mechanics. I can see the "oil jocky" bumping things around. Nice visual, raggie.

So switching to synthetic isn't a concern I take it.

Man, auto trouble is the one thing that can invoke wild imaginings in me. This truck has been a jewel but I've had big trouble in other vehicals and it can just ruin a day, or week or couple months.

Thanks, Chritoph and raggie.


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## DieselDave (Jan 16, 2006)

1. Why did they go to syn. without asking you? An oil change with regular oil is $20-$25 but with syn. it raises to about $50. What did they charge you?

2 I have never seen anyone (commercially) fill a oil filter before installing. You fill a fuel filter but I don't believe you need to fill an oil filter. Many oil filters are mounted open end down so they would be impossible to fill prior to installation. Point being, that should not be an issue.

3. Odds are very high you have an oil pressure sensor failure.

Lighter side. I drove my Dad's truck last year and was running down the highway at 70 MPH. I looked over and noticed the oil pressure was at 0. I immediately turned the truck off and coasted to a stop on the side of the highway. I checked the oil level, looked for leaks but everything seemed fine. I finally got my Dad on the phone and he said, "Oh yea, I meant to tell you the gauge has gone bad. I restarted the truck and the gauge worked normally for a while.

If the pressure is really 0 I think you would hear an odd noise from the engine but don't know for sure.


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## pedalinbob (Jan 16, 2006)

I doubt the change to synthetic would cause a pressure drop.

Like others mentioned, check the oil pressure sending unit (likely electronic, not mechanical), and consider the filter itself.

I have seen some odd things happen with a goofed filter.
Some have a built in bypass in case the filter clogs. That bypass can be screwed up right from the factory, causing strangeness, especially if it is located near the sensor.

Or, some engine blocks have a spring loaded bypass. It could be sticky.

Also, if the pressure is truly dropping to zero, and you have hydraulic lifters, they will start clacking loudly. If not, the pressure is not zero.

I admit I do not know your engine, and not sure if these issues could cause the symptoms you describe--just food for thought!

Bob


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## Jumpmaster (Jan 16, 2006)

My understanding (since I just switched) was that if you use regular oil and then switch to synthetic, you're not supposed to switch back to regular oil again because the synthetic "does something" to the rings...though the parts guy couldn't tell me exactly what that "something" would be...

I just planned on keeping synthetic in it from now on anyway...it has 46k on it and I plan on driving it for a long time...used the Mobile synth this time...might try Royal Purple next -- heard good things about it.

JM-99


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## raggie33 (Jan 16, 2006)

man id say im almsot sure it would kncok like crazy if the presure was o i forget what oil presure should be at idle but id guess 20 to 30 but its been a while so i forget


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## Icebreak (Jan 16, 2006)

JM-99 –

Good to know.

Lightmeup –

Yeah I know I’ve heard that but I can’t remember if it was speculative do do or not.

DeiselDave –

1 I think your question answered itself. More money. The receipt is at the office. Now it sounds like I’m stuck with synthetic for the life of the truck. We’ll I’ve heard it was better but that should have been my choice. 
2 I used to fill the filter just cause I heard it was correct. Didn’t really understand why so no more of that. This helps cause I may have suggested it without talking to you guys first.
3 That’s what it sounds like, yes. Thanks for the confirmation.
Runs quiet and smooth.

Gee thanks for the rush, Pop. Dads are funny cause all you can do is smile when they do stuff like that. 

pedallianbob –

That’s helpful info. Maybe I get them to check the sensor and give me a new filter just in case. You know considering the bill was double what it should have been. Yes, no clacking.

JM-99 –

OK. I’m feeling a little better about it now. My memory is coming back. I was going to go to Royal Purple in my old Toyota years ago.

raggie33 –

I’m sure you are right. I remember the sensor wires and connectors being kinda in the way.

Don’t you just love CPF? Six people with excellent information in a matter of minutes. I have the day off work today so I’m not going to blow the afternoon at the shop. Just take in the morning. Pick it up at lunch.

Thanks, gentlemen. Send me a bill for the diagnostics and consulting if you must.


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## nickz (Jan 16, 2006)

The switch to synthetic after use of "dino" oils is an issue of the detergents used in the synthetic oil. Standard or "dino" oil has a tendancy to build deposits in your engine. The high detergent content of synthetic oils is said to cause these deposits to break loose and circulate through your engine until your filter catches the particles. It is the circulation of these built up particles that is said to cause engine damage.


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## dano (Jan 16, 2006)

Switching from Dino to Synthetic isn't a problem, neither is going from one to the other in intervals. Synthetic does not harm engine seals, piston rings, etc. All that is a myth.

A jumpy gauge is probably a problem with the gauge and/or gauge pick-up assembly/sensor.

-dan


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## Jumpmaster (Jan 16, 2006)

Icebreak said:


> 2 I used to fill the filter just cause I heard it was correct. Didn’t really understand why so no more of that. This helps cause I may have suggested it without talking to you guys first.



That may have been a throwback from older motors...I had a 1952 M38A1 (military Jeep the CJ-5 was modeled after) and it had the paper cartridge type filter that went into a little container above the engine (!)...I had to put the filter in, then fill that part with oil.

Thanks for the info, Dano...glad I can switch back if I find myself in the po-house!

JM-99


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## cy (Jan 16, 2006)

going from non detergent oil used the 50's to modern detergent oils could possibly cause problems. 

my 1954 Austin Healey 100-4 uses non-detergent oil. I'm afraid to run detergent oil for fear it will desolve oil buildup film on critical parts. needless to say it's hard to find, got a small stash of non detergent oil.

if your oil pressure was truly zero, you would know within a few miles. engine will destroy itself in short order.


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## raggie33 (Jan 16, 2006)

cy said:


> going from non detergent oil used the 50's to modern detergent oils could possibly cause problems.
> 
> my 1954 Austin Healey 100-4 uses non-detergent oil. I'm afraid to run detergent oil for fear it will desolve oil buildup film on critical parts. needless to say it's hard to find, got a small stash of non detergent oil.


look for air compreser oil aint it like 30 nd?but i may be wrong


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## Christoph (Jan 16, 2006)

Ya beat me to it raggie yes compressor oil is non detergent.there are even some synth compressor oils non det.

C


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## tvodrd (Jan 16, 2006)

I love the smell of "bean oil" in the morning, smells like ........the race track! (Sorry for the O.T.  )

Larry


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## cy (Jan 16, 2006)

yep, caster bean oil for two strokes;;;


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## Moat (Jan 17, 2006)

Dano is right - there were some issues with synthetics when they first became commercially available for autos (mid 70's?), but have long since been resolved in any current oils. High natural detergency, oil seal incompatibility/shrinkage (leaks), IIRC.

The fill-the-filter thing is not a bad idea, as there are initially a few seconds where there is no oil pressure (as the empty, new filter fills with oil) - although the residual oil film on/between parts appears sufficient... millions of empty-filter changes with no real problems seem to support that. (although I still like to fill 'em on my bikes/pickup, if possible... just because!).

If it's not the gauge acting up, I'd tend to replace the filter - could be a bad/mis-located anti-drainback flapper in the filter or something (?)... cheap insurance, anyhoo.

I've done a fair amount of reading re; synth vs. dino, and conclude that dino is fine... but for a little xtra $$, synth is the way to go. Mobil 1, in particular.

Let us know what you find, Jeff!


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## Unicorn (Jan 17, 2006)

cy said:


> going from non detergent oil used the 50's to modern detergent oils could possibly cause problems.
> 
> my 1954 Austin Healey 100-4 uses non-detergent oil. I'm afraid to run detergent oil for fear it will desolve oil buildup film on critical parts. needless to say it's hard to find, got a small stash of non detergent oil.
> 
> if your oil pressure was truly zero, you would know within a few miles. engine will destroy itself in short order.



Isn't racing oil usually non-detergent?


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