Mobil T&S 5w 40 & Pinging

[Hirev]

I own a 91 Toyota v6 truck I bought new. In May of 05 I changed to Mobil T&S within a week I noticed some off idle, mild pinging if the clutch was not let out easy. What was strange is I never had this problem in the 14 years I have owned this truck. I got my gas at one of two Chevron gas station for more than 10 years.

In December 05 I changed out the Mobil T&S to some Chevron 5w 30 SL. The pinging stopped within a day and has not pinged since. This truck uses very little oil about 1 qt in 3500 miles.

I now realize it was the Mobil 5w 40 T&S oil that was causing this problem.

I have used many oils in it life but none of the others did this. Such as Chevron 5w 30, 10w 30, 15w 40 HDEO, Mobil 1 10w 30, Mobil 0w 40, Mobil 15w 40 HDEO 1300, Along with some early synthetic Castrol, GC and GTX.

Question: Has anyone else had this problem with Mobil T&S?

 

[Ed_T]

Sounds like coincidence.

 

[bar1]

Could be a leaky rear crank seal.
But it's probably not

Have your ignition system, fuel system and air intake system checked.

 

[gtoracer]

I have experienced this with M1-10w-30 in my 93 5.7Chev truck, IMHO any synthetic provides a better seal in the ringpak and thus raises cyl pressures and effiency, having said that I would ask if that older engine has a o2 sensor, if not it would not be able to adjust for the raised cyl pressure thus the pinging...Pete

 

[GoldenRod]

"I have experienced this with M1-10w-30 in my 93 5.7Chev truck, IMHO any synthetic provides a better seal in the ringpak and thus raises cyl pressures and effiency, having said that I would ask if that older engine has a o2 sensor, if not it would not be able to adjust for the raised cyl pressure thus the pinging...Pete"
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That has got to be one of the most interesting things I have read in a long time.

 

[Hirev]

quote:

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I have experienced this with M1-10w-30 in my 93 5.7Chev truck, IMHO any synthetic provides a better seal in the ringpak and thus raises cyl pressures and effiency, having said that I would ask if that older engine has a o2 sensor, if not it would not be able to adjust for the raised cyl pressure thus the pinging...Pete

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Yes the motor has EFI and a O2 sensor.

I used Mobil 1 10w 30 a lot in its life (in older formulas) in this motor and never had the problem.

 

[Thingfish]

What does an 02 have to do with detecting knock ?
An 02 strictly measures oxygen content to determine mixture, or catalyst function on OBD2 vehicles. ( to check if the cats are working )
Ring blowby is a mixture of air and fuel, an o2 would still see the same mixture, just more of it from less blowby.

However, IF it is making a better seal and making more cylinder pressure.... The answer could be right there.... pressure = temperature.

 

[1sttruck]

Another possibility.... does the truck have hydraulic lifters ? If so the heavier oil may changed how the lifters actuate, slighly chnaging the valve timing ? If so you should notice a similar pinging at start up when it's cold out.

 

[gtoracer]

I have experienced this with M1-10w-30 in my 93 5.7Chev truck, IMHO any synthetic provides a better seal in the ringpak and thus raises cyl pressures and effiency, having said that I would ask if that older engine has a o2 sensor, if not it would not be able to adjust for the raised cyl pressure thus the pinging...Pete


Sorry guys my bad,I meant knock sensor
What made me think this was,it got worse when I went to 5w-40 T & suv, also the pinging went away when I switched to 93 octane gas.......Pete

[ January 21, 2006, 04:03 PM: Message edited by: gtoracer ]

 

[Geoff]

The higher viscosity is probably having the effect of sealing your cylinders better - and therefore raising your compression ratio. Higher compression needs higher octane or you get pinging. Also, on an older engine, you'll have carbon buildup inside the cylinders that will effectively increase compression since it is "filling up" the volume.

I have run water through the intake via a small vacuum hose on a hot engine at fast idle and it cleans the carbon right out. It steam cleans the cylinders. Don't use a diameter larger hose than about 3mm.

 

[Propflux01]

If the engine burns even a slight amount of oil, that burning oil can/will cause pinging. perhaps the mobil's 5w portion was alittle too thin for the clearances of your engine.

 

[Hirev]

I just find it so odd that the problem stopped completely once I changed over to 5w 30 Chevron from the Mobil T&S.

To answer a ? above the motor uses a solid lifter cam so no Hyd lifters to cause problems.