5W20 Towing and Hot Idle PSI

[Winston]

So, I went thin with my '95 Mitsu Montero with 163,000 miles. This truck is a bit under powered with a 3.0L V6 with 172 hp.

I just used it to tow my 2500lb tent trailer up Mount Diablo in Contra Costa County, CA. It was a short trip, about 30 minutes in 95F heat with the AC going full blast. It is a pretty steep drive and the truck has to work pretty hard. When I reached the campground and let the truck idle, I still had 15psi at idle. This is the same hot idle temp that I got with 5W30 or 10W30 oil.

Just wanted to share.

Thin seems good to me.

 

[buster]

Cool. What 5w-20 are you using? I'm running the Red Line 5w-20 and so far it has shown less evaporation than other 5w-20's.

 

[Drew99GT]

Jimminy, do you want that engine to die a painful death?

I can relate, driving in the mountains of Colorado. Unfortunately, thin is not in with my father's 98 Blazer. Under mountain pass conditions in high heat with 5w30, the idle oil pressure use to drop a hair under 20 psi. I haven't actually driven up into the mountains this summer in the souring heat yet, but the last few years, I could get the pressure to stay above 20 psi with 10w30 and a quart or two of 15w40.

Can you tell a power or mileage difference with the 5w-20 under the high heat conditions?

 

[Winston]

I am using Motorcraft 5W20. It has had flawless used oil analysis so I trust it is well formulated, and it was not too expensive at Walmart.

I don't notice much difference in power. It "seems" to rev a bit easier, but I think that is imaginary.

 

[Gary Allan]

Any observations with your dynamic oil pressure readings, Winston? That is, how was the pressure while climbing the great mountain?

I doubt you'll see any difference at all in "power" or 'butt dyno' ..cept when cold ..and it doesn't look like cold is in your normal seasonal span.

 

[Slick 55]

What is your reasoning to use 5W-20 in an engine that does not recommend it?

 

[Louie's gone fishing]

Thanks for a real 'hands-on' comment on 5w-20. Could it be that a good 5w-20 can do th job, even in an engine not spec'd for it?

 

[427Z06]

Thanks for sharing, Winston.

I believe Gary has a similar test planned. But with his luck, his right sun-visor will slip into the down position and the spare tire will loose it's air.

 

[JohnBrowning]

Make sure you do a used oil analysis so we can see how 5W20 is doing in this engine. I love seeing how engines behave to oils that are thicker or thinner then recoemended. We seldom get a used oil analysis out of anyone that is running 5W20 in an engine not recomending it! We really need to see more of thes so we can see how many engines especialy older designs do when running thinner then recomended oils viscosities.

Like wise we never see any used oil analysis from anyone that use's MMO for any part of their OCI.

 

[Gary Allan]

quote:

---

Originally posted by 427Z06:
Thanks for sharing, Winston.

I believe Gary has a similar test planned.

---

Shhh! You'll ruin the dramatic impact!! This could be up there with ***-Wee's Big Adenture!

quote:

---

Originally posted by 427Z06:
But with his luck, his right sun-visor will slip into the down position and the spare tire will loose it's air.

---

Yes. Several interior fixtures are put at risk here. (visions of Bones in "The Search for Spock"). I choose the danger!

 

[Winston]

quote:

---

Any observations with your dynamic oil pressure readings

---

The oil pressure gauge is heavily "dampened." It moves very slowly. When driving around the pressure stays right around 45-50psi, which is just past the middle position of the gauge. When reved up it does not get much past 60psi. These readings are all similar to the readings I got with other 5W30 and 10W30 oil. The only difference I saw was lower pressures on cold startup. Although my "cold" startup this morning was at 60F at 6:30 this morning.

quote:

---

What is your reasoning to use 5W-20 in an engine that does not recommend it?

---

I was just curious. So much debate about thin oils, I thought I would try one. I don't think it will affect the life of this engine much. Plus, the vehicle has an oil pressure gauge, so I can monitor the pressure to see if the thinner oil causes any dramatic oil pressure problems. If there were problems with oil pressure I would have drained out the oil. Seems like the oil pressure is A-OK. I will run this oil out to about 7000 miles and do a used oil analysis.(about 5-6 months)