My GM 3100 has the typical piston slap. Last weekend I had the engine torn down to replace the intake manifold gaskets (as preventive maintenance, there weren't leaking) and I put some cheap 10w40 in and the piston slap was gone. Ran engine flush and put amsoil 5w30 (recommended viscosity by gm) and it was back. My question is should I, and would it be safe to, replace the Amsoil 5w30 with Amsoil 5w40 to get rid of the sounds? I read that the piston slap in these engines are nothing to worry about, however a car with only 50K on it that sounds like a deisel at startup is annoying. Whats your thoughts?
Piston Slap and oil question
- Thread starter HACCOFFICER
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I feel your pain. I used to get GM dealership oil changes and they used regular Mobil. And mine slapped like crazy at start-up. I started using Chevron Supreme 10W-30 and now it sounds like a sewing machine. I had a previous truck that I used Pennzoil 10W-30 and then moved to Mobil 1 10W-30, the Pennzoil was awful, the truck slapped all the time. With the Mobil 1 is still pinged at start-up but not all the time. But the Chevron oil has done better than any of the rest. If I get to where I can't find Chevron Supreme, Im gonna use Havoline.
I have a 3100 also. It is 9 years old, 100K and has barely slapped for a minute or so on cold start since new. Always used Trop-Artic. When they changed the formula to semi-synthetic, it quieted it down, but is not annoying, or abnormal. Do a search on this with the key word piston slap. I remember a poster who said that 10-30 Castrol synthetic helped the most. Someone else said high moly content oils helped. Valvoline sythentic oil additive was also mentioned.
Sorry I have no experience with Amsoil, and I know I did not really answer your question, but I hope my .02 helps.
Sorry I have no experience with Amsoil, and I know I did not really answer your question, but I hope my .02 helps.
A thicker oil "takes up the space" between the piston skirt and the cylinder wall per se. This is a band aid fix though. The real fix is to replace the pistons and have the bores honed or bored.
I have a GM 3100 engine in a Lumina with 70,000 some miles and it does not slap and never has.
btw-Amsoil synthetic in it from the first oil change.
btw-Amsoil synthetic in it from the first oil change.
Would a 10w 30 be better for this or the 5w40. I am looking for the extra cushion until the pistons warm and expand. I have no problem with continuing to use 5w30. I need this car to go the next 5 years so I dont want this "piston slap" to get worse. I am sold on Amsoil, unless I can find one with better anti-wear capabilities.
Mine has had a tap since new.
A thicker oil reduces the tap.
My decision has been to run thicker oil.
A thicker oil reduces the tap.
My decision has been to run thicker oil.
How much thicker do you think? 5w40 10w30
A 10w30 will allow less slap noise than 5w30, since it is thicker during the warup phase. A straight 30 would be even better. A 5w40 or 5w50 might have the same amount of slap as 5w30 if the thickness during warmup is the same.
Cool so 10w30 it is!
Here's a dumb question. What does piston slap sound like?
"Here's a dumb question. What does piston slap sound like? " Ot spimds like a diesel. It is somewhat more audible if you get down and listen to the lower part of the engine. It should go away after a minute or so.
HACCOFFICER: I wouldn't go with a 10W in Pa. unless its a synthetic.
HACCOFFICER: I wouldn't go with a 10W in Pa. unless its a synthetic.
It does go away after the engine warms some. Gm 3100's have this I hear
My GM 3100 (112,000 miles) has been running strong since 35k even though it rattles its *** off on cold-starts.
Piston slap will not affect the longevity, performance, or fuel mileage of your engine. Its just an annoyance.
Piston slap will not affect the longevity, performance, or fuel mileage of your engine. Its just an annoyance.
I use a 10w30 in my 3100 (Lumina). For a long time now, I have had a very slight lifter tick for about the first 30 seconds after the car is turned on (seems slightly louder in the winter). Otherwise, when the car is warmed up, you can barely hear it running. Never had any problems with piston slap though.
Just out of curiosity HACCOFFICER, what would I be getting into if I decided to replace the intake manifold gaskets on my car? I have heard problems with these gaskets are common in this engine.
Just out of curiosity HACCOFFICER, what would I be getting into if I decided to replace the intake manifold gaskets on my car? I have heard problems with these gaskets are common in this engine.
Johnsmith-There not that hard to do. It will take a day if you have the right tools. Get fel-pros perma dry gaskets which is a metal, rubber gasket that is the solution to the problem. Get yourselve a good repair manual. It was not nearly as hard as I thought it was going to be. When I took the old gaskets out I noticed they were beginning to go bad (splitting) so I got them right on time.
" I have heard problems with these gaskets are common in this engine."
Its really more like inevitable. Your odds (from what I have seen) are that by 60K you will have a leak. It may not be enough to kill the engine, but it will almost certainly exist.
Its really more like inevitable. Your odds (from what I have seen) are that by 60K you will have a leak. It may not be enough to kill the engine, but it will almost certainly exist.
Dang!
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