demtek9

Actually It has gotten better just by changing the way I drive it. Instead of lugging it around trying to save gas, I just drive it as any normal car or truck and let the engine rev.
I just got an article in an off road magazine that said the same thing. Drive the 3.8 like you don't like it and it will do better. Seems to be working.
I'll try that seafoam treatment at the next oil change too.

crodgers618

That's what i was told got my first oil change and put in the 5w30 after 4 days the motor started to rattle when under load and felt like it was losing power asked around on here and got some different answers. Finally got a hold of my buddy he has 2 Jeeps and works on cars he said to get that oil out and go with 10w40 i changed it after 2 weeks and one day later what a difference no ping our knocking on start up runs real quite no noise from the motor at all and I do have more power. I'm putting in a fuel system cleaner today and I'll see what that does. I have a 07 with just about 41000 on it. Bought it used.

13rubi

This makes sense. Puttting a more viscous liquid into the same space ( oil clearance of main bearings ) will increace oil pressure which in turn will prematurley wear out bearings not designed to work at that pressure. This is called bearing errosion. I would also expect to see and increase in tin and babbit in your oil too. Did you do and control pre 5/30 samples to compare? A thicke oil can also cause more wear on cold starts. As a dealer tech for over 17 years I am a big believer in using the manufactuers recamended oil wts. I have seen too many damaged engines with denied waranty claims to think othe wise IMHO.

Uneasy Rider

Dude. That makes no sense. LMAO

Flip94ta

I was waiting for somebody to say it.

FallschirmJaeger

That's interesting, seems there are mixed reviews.

Sounds like I won't be able to do this "trick," being that I'm in the MidWest. Summers get 100+, however, Winters fall very cold.

Mine's a JK '07, Manual 6speed, 3.8L. I'll keep an eye on this for the future, though.

Just changed my oil this weekend, used 5W20 royal purple, and then used a pint of the seafoam fuel cleaner. Still waiting to drain the tank and see any differences with the injection.

Mr.T

Here's my 2 cents... Oil viscosity changes quite a bit with temperature. Engines have to be designed to handle variations in oil temperature, which is going to vary with RPM, power, ambient temp, etc.

One can use a viscosity calculator such as the one at bobistheoilguy, along with the viscosity specs for a 5w-20 oil at 100 and 40 Deg C, then figure how much temperature reduction from 100 C would make the 5w-20 oil equal the 100 C viscosity of another oil.

Just compared a 5w-20 with a 5w-40, there's about 18 deg difference in temperature (near 100 deg C) for equal viscosity in cSt. So 5w-40 is like running 5w-20 at 18 deg cooler temperature. And since they are both 5w for the winter rating, they have roughly equivalent viscosity for cold weather startup viscosity.

Bottom line, I'm not concerned about any bad side affects, other than a slight MPG loss, from substituting 5w-40 for a 5w-20. I've used 5w-20 and 30, and am running 5w-40 now. This engine doesn't use oil even with 5w-20, but there is a slight audible difference -- more like a Mercedes with 5w-40. Driving in Death Valley in summer, and the Oregon mountains in winter, 5w-40 synthetic makes sense for me. At some cold start temperature, a 15w-X becomes a limiting factor.

Dronac

I didn't do a control with 5w-20, though there is a noticeable decrease in engine noise with 5w-30. Plus, I did a run of 5w-40 and all wear metals were down below the 5w-30 wear levels (Rotella 5w-40 diesel oil compared to Royal Purple 5w-30 and Penzzoil Platinum 5w-30).


In this picture, the current (leftmost) numbers are from Rotella 5w-40 Diesel oil. The next two are Royal Purple 5w-30, and the last is Penzzoil Platinum 5w-30

aldaman

thanks for sharing. I am not too familiar with reading the report, but if I interpreted it correctly did the Penzoil brand provide better protection over Royal purple?

Specifically! I was comparing the #s from:

Aluminum
Copper
SUS
cSt

Dronac

Not exactly. The Penzoil was only run for 3,000 miles, vs 5,000 for all the others. Doing a rough estimation in my head, I believe the copper falls in between the Royal Purple runs mile per mile, while other metals are higher, even at just 3k miles. SUS and cSt shows that the viscosity at those temps was less then the RP, though only very slightly. The "expected ranges" column only applies to the 5w-40 sample on this sheet.

On a side note, Rotella 5w-40 did give me occasional start up noise in the winter, but regardless, the oil sample was still better. I'v got 5w-30 in my engine now as I wanted to see the results of this last sample before sticking to 5w-40, and I'll probably sample it as another control sample. Next time I'm giving Mobile 1 5w-40 a shot to try and avoid start up noise, as it tends to have a bit better cold flow.

Man... I'v spent too much time on bobistheoilguy forums.