Idle oil pressure 5w30 vs 5w40

Status
Not open for further replies.
Joined
Dec 31, 2017
Messages
15,069
Location
SE British Columbia, Canada
I've tried out some 5w40 in my Chev 6.0 with 180,000 miles. The 5w30 was QSUD with a Kv100 of 11 cSt. The 5w40 was Motomaster Formula 1 made by Citgo. Sorry but no Kv100 at this point but probably around 14 cSt.

Here are the two shots of the oil pressure gage at a full 210 deg with the same run down the highway and back. Just one or two psi difference at idle. The highway oil pressures were also within a few psi, at 40 psi and just above. ( of course the highway pressures would have been regulated.) The pressure sensor on this engine is at the back of the driver's side head. I wasn't sure what to expect, so I posted this to see what others may have experienced.
smile.gif


First pic: 5w30. 2nd pic 5w40. Enjoy.


9ABC643B-CE63-4029-A0B0-3689B60E0C5C.jpeg


F787DF57-9F3C-4F6B-8A36-B5C4096A997B.jpeg
 
Last edited:
so to clarify the pictures were taken at idle following a highway run to heat it up?
 
Originally Posted by Rand
so to clarify the pictures were taken at idle following a highway run to heat it up?


Yes, about 5 miles each way. Same route, pretty much same ambient temp.
 
Expected results, really. Not really beneficial, imo, but you just testing out a hypothesis? Does engine consume oil? You tow heavy with this truck?
 
Not surprised. It's about the same on my 5.6 Titan after a short highway milk run like that. Not much diff.

After 3 hour 7500 lb tow through the desert at 100+ the idle pressure becomes pronounced between 30 and 40.

An all aluminum block and heads in my rig doenst typically help.

Not enough to make me worry but certainly enough to see a notable diff in pressure.



UD
 
Last edited:
Can you hook up an OBDII reader and get the actual pressure readings?
 
Originally Posted by bmwtechguy
Expected results, really. Not really beneficial, imo, but you just testing out a hypothesis? Does engine consume oil? You tow heavy with this truck?


Yes, just checking. Doesn't consume oil. I tow a 28 ft trailer at temps up to 90C.
 
My lq4 engine runs 15-20 psi hot idle and around 35-40 at highway speeds on 10w30. Lucas oil stabilizer seemed to add around 3-5 psi average.
 
Does your gauge has a resistor built in (to stay in place....resistors serve as a buffer zone)....its the sam as @ temperature gauge...it is always at 90'C no matter what is the ambient temperature outside...
wink.gif
 
Originally Posted by Kamele0N
Does your gauge has a resistor built in (to stay in place....resistors serve as a buffer zone)....its the sam as @ temperature gauge...it is always at 90'C no matter what is the ambient temperature outside...
wink.gif




The oil pressure reading seems to be sensitive. The temp gauge seems to rise in the first 5 minutes after startup, reaches 210 F then stays there without moving.
 
GM seems to make an effort to indicate actual oil pressure, Dodge/Ram & Ford just put the gauge somewhere in the "normal" zone. Makes one wonder why they just didn't use an idiot light, dummy gauge is about as useful!
 
Originally Posted by Snagglefoot
I've tried out some 5w40 in my Chev 6.0 with 180,000 miles. The 5w30 was QSUD with a Kv100 of 11 cSt. The 5w40 was Motomaster Formula 1 made by Citgo. Sorry but no Kv100 at this point but probably around 14 cSt.

Here are the two shots of the oil pressure gage at a full 210 deg with the same run down the highway and back. Just one or two psi difference at idle. The highway oil pressures were also within a few psi, at 40 psi and just above. ( of course the highway pressures would have been regulated.) The pressure sensor on this engine is at the back of the driver's side head. I wasn't sure what to expect, so I posted this to see what others may have experienced.
smile.gif


First pic: 5w30. 2nd pic 5w40. Enjoy.

Thanks for posting this.

I had estimated the HTHSV for QSUD 5W-30 SN PLUS as 3.3 cP using my base-oil viscosity calculator. If the 5W-40 has HTHSV = 3.6 cP, then that's 10% difference in oil pressure; so, 28 psi vs. 31 psi sounds just right.

You wouldn't see this oil-pressure behavior with a typical Resource Conserving (ILSAC) 5W-30 though. QSUD 5W-30 SN PLUS has an unusually large HTHSV.
 
Status
Not open for further replies.
Back
Top