Is there anything wrong with using 20w50 oil?

[Bullet]

My truck is a 1994 with over 120,000 miles. I changed the oil today withe penz 10w30, I've been using 5w and 10w 30 for most part. I was listening close to the noise in the engine. Some clatter from the rockers and probably piston slap. This noise has been there for years and has good oil pressure.

The engine doesn't burn a drop of oil. Once driving in a flood water when down the intake and locked the engine. After a few minutes the water squeezed past the pistons and started. The next day I changed the oil 3xs. That was in 1997 or 98.

Does a thicker oil help control piston slap?

 

[wavinwayne]

I have no clue whether using 20w50 will control piston slap (it might

), but to answer the question posted in your topic title:

No, there is nothing WRONG with using 20w50 oil, assuming you don't run it in -20° weather. From what I've gathered here on BITOG, you CAN run 20w50 in any modern gas-powered engine; the possible downside that comes to mind is that your MPG may drop a little.

 

[drive it forever]

My opinion is that using a thicker oil will accelerate engine wear. I would use a 15w40 diesel engine oil before I would a 20w50. A thicker oil might cushion the parts a little better, but, as the claim goes, most engine wear is from engine start up. Using 20w50 over a 5 or 10w30 will cause your engine life to decrease because of the thicker viscosity at start up. If the noise has been there for years and the truck has 120k on it, I would stick with what you have been doing/using. This is my opinion.

 

[jorton]

This is a most complicated topic.

I think the best grade is 10w-40 because it's mid-way between the lowest and highest viscosity, but the best formulation is 5w-30 because that's what most auto manufacturers use in new cars.

I know mechanics and machine shops and race engine builders who use 20w-50.

I never heard of piston slap before 1997. Your's may be a rod or wrist pin from when it was hydro-locked.

 

[theguru]

To control piston slap in the Oz LS-1's they speced Mobil 1 10w-30.

 

[mikemc]

10w30 is a great all-around oil for gassers that are in good mechanical condition. I would be hesitant to move up to 20w50 since your truck is not burning oil.

 

[jthorner]

A slightly thicker oil might be helpful if your piston to bore clearances are growing.

If you want to go a little thicker, the first step would be a "high mileage" 10W-30 as they tend to the thicker side of the 30 weight spec. After that would be a 15W-40 fleet oil (often wrongly called a diesel oil).

10W-40 is IMO a useless grade as the available 15W-40s are generally more shear stable and I wouldn't use a 10W-40 or a 15W-40 in severe winter conditions.

20W-50 would probably work ok, but the reduced performance and fuel economy would give you little back in return.

John

 

[BlazerLT]

Thicker oil will not stop piston slap.

Stick with the 10w30.

 

[gianmarco]

in some countries 20W-50 is all you can find! I wonder the reason for this, in Peru for example 20w-50 is the standard weight offered everywhere, sure you can find some synth but they cost as much as 5 or 6 X dino...wierd uh?